March 2025 - Linux-kselftest-mirror

[PATCH 0/3] RISC-V KVM selftests improvements

by Atish Patra

This series improves the following tests. 1. Get-reg-list : Adds vector support 2. SBI PMU test : Distinguish between different types of illegal exception The first patch is just helper patch that adds stval support during exception handling. Signed-off-by: Atish Patra <atishp(a)rivosinc.com> --- Atish Patra (3): KVM: riscv: selftests: Add stval to exception handling KVM: riscv: selftests: Decode stval to identify exact exception type KVM: riscv: selftests: Add vector extension tests .../selftests/kvm/include/riscv/processor.h | 1 + tools/testing/selftests/kvm/lib/riscv/handlers.S | 2 + tools/testing/selftests/kvm/riscv/get-reg-list.c | 111 ++++++++++++++++++++- tools/testing/selftests/kvm/riscv/sbi_pmu_test.c | 32 ++++++ 4 files changed, 145 insertions(+), 1 deletion(-) --- base-commit: b3f263a98d30fe2e33eefea297598c590ee3560e change-id: 20250324-kvm_selftest_improve-9bedb9f0a6d3 -- Regards, Atish patra

41 minutes

4
14
0 0

[RFC PATCH 00/39] 1G page support for guest_memfd

by Ackerley Tng

Hello, This patchset is our exploration of how to support 1G pages in guest_memfd, and how the pages will be used in Confidential VMs. The patchset covers: + How to get 1G pages + Allowing mmap() of guest_memfd to userspace so that both private and shared memory can use the same physical pages + Splitting and reconstructing pages to support conversions and mmap() + How the VM, userspace and guest_memfd interact to support conversions + Selftests to test all the above + Selftests also demonstrate the conversion flow between VM, userspace and guest_memfd. Why 1G pages in guest memfd? Bring guest_memfd to performance and memory savings parity with VMs that are backed by HugeTLBfs. + Performance is improved with 1G pages by more TLB hits and faster page walks on TLB misses. + Memory savings from 1G pages comes from HugeTLB Vmemmap Optimization (HVO). Options for 1G page support: 1. HugeTLB 2. Contiguous Memory Allocator (CMA) 3. Other suggestions are welcome! Comparison between options: 1. HugeTLB + Refactor HugeTLB to separate allocator from the rest of HugeTLB + Pro: Graceful transition for VMs backed with HugeTLB to guest_memfd + Near term: Allows co-tenancy of HugeTLB and guest_memfd backed VMs + Pro: Can provide iterative steps toward new future allocator + Unexplored: Managing userspace-visible changes + e.g. HugeTLB's free_hugepages will decrease if HugeTLB is used, but not when future allocator is used 2. CMA + Port some HugeTLB features to be applied on CMA + Pro: Clean slate What would refactoring HugeTLB involve? (Some refactoring was done in this RFC, more can be done.) 1. Broadly involves separating the HugeTLB allocator from the rest of HugeTLB + Brings more modularity to HugeTLB + No functionality change intended + Likely step towards HugeTLB's integration into core-mm 2. guest_memfd will use just the allocator component of HugeTLB, not including the complex parts of HugeTLB like + Userspace reservations (resv_map) + Shared PMD mappings + Special page walkers What features would need to be ported to CMA? + Improved allocation guarantees + Per NUMA node pool of huge pages + Subpools per guest_memfd + Memory savings + Something like HugeTLB Vmemmap Optimization + Configuration/reporting features + Configuration of number of pages available (and per NUMA node) at and after host boot + Reporting of memory usage/availability statistics at runtime HugeTLB was picked as the source of 1G pages for this RFC because it allows a graceful transition, and retains memory savings from HVO. To illustrate this, if a host machine uses HugeTLBfs to back VMs, and a confidential VM were to be scheduled on that host, some HugeTLBfs pages would have to be given up and returned to CMA for guest_memfd pages to be rebuilt from that memory. This requires memory to be reserved for HVO to be removed and reapplied on the new guest_memfd memory. This not only slows down memory allocation but also trims the benefits of HVO. Memory would have to be reserved on the host to facilitate these transitions. Improving how guest_memfd uses the allocator in a future revision of this RFC: To provide an easier transition away from HugeTLB, guest_memfd's use of HugeTLB should be limited to these allocator functions: + reserve(node, page_size, num_pages) => opaque handle + Used when a guest_memfd inode is created to reserve memory from backend allocator + allocate(handle, mempolicy, page_size) => folio + To allocate a folio from guest_memfd's reservation + split(handle, folio, target_page_size) => void + To take a huge folio, and split it to smaller folios, restore to filemap + reconstruct(handle, first_folio, nr_pages) => void + To take a folio, and reconstruct a huge folio out of nr_pages from the first_folio + free(handle, folio) => void + To return folio to guest_memfd's reservation + error(handle, folio) => void + To handle memory errors + unreserve(handle) => void + To return guest_memfd's reservation to allocator backend Userspace should only provide a page size when creating a guest_memfd and should not have to specify HugeTLB. Overview of patches: + Patches 01-12 + Many small changes to HugeTLB, mostly to separate HugeTLBfs concepts from HugeTLB, and to expose HugeTLB functions. + Patches 13-16 + Letting guest_memfd use HugeTLB + Creation of each guest_memfd reserves pages from HugeTLB's global hstate and puts it into the guest_memfd inode's subpool + Each folio allocation takes a page from the guest_memfd inode's subpool + Patches 17-21 + Selftests for new HugeTLB features in guest_memfd + Patches 22-24 + More small changes on the HugeTLB side to expose functions needed by guest_memfd + Patch 25: + Uses the newly available functions from patches 22-24 to split HugeTLB pages. In this patch, HugeTLB folios are always split to 4K before any usage, private or shared. + Patches 26-28 + Allow mmap() in guest_memfd and faulting in shared pages + Patch 29 + Enables conversion between private/shared pages + Patch 30 + Required to zero folios after conversions to avoid leaking initialized kernel memory + Patch 31-38 + Add selftests to test mapping pages to userspace, guest/host memory sharing and update conversions tests + Patch 33 illustrates the conversion flow between VM/userspace/guest_memfd + Patch 39 + Dynamically split and reconstruct HugeTLB pages instead of always splitting before use. All earlier selftests are expected to still pass. TODOs: + Add logic to wait for safe_refcount [1] + Look into lazy splitting/reconstruction of pages + Currently, when the KVM_SET_MEMORY_ATTRIBUTES is invoked, not only is the mem_attr_array and faultability updated, the pages in the requested range are also split/reconstructed as necessary. We want to look into delaying splitting/reconstruction to fault time. + Solve race between folios being faulted in and being truncated + When running private_mem_conversions_test with more than 1 vCPU, a folio getting truncated may get faulted in by another process, causing elevated mapcounts when the folio is freed (VM_BUG_ON_FOLIO). + Add intermediate splits (1G should first split to 2M and not split directly to 4K) + Use guest's lock instead of hugetlb_lock + Use multi-index xarray/replace xarray with some other data struct for faultability flag + Refactor HugeTLB better, present generic allocator interface Please let us know your thoughts on: + HugeTLB as the choice of transitional allocator backend + Refactoring HugeTLB to provide generic allocator interface + Shared/private conversion flow + Requiring user to request kernel to unmap pages from userspace using madvise(MADV_DONTNEED) + Failing conversion on elevated mapcounts/pincounts/refcounts + Process of splitting/reconstructing page + Anything else! [1] https://lore.kernel.org/all/20240829-guest-memfd-lib-v2-0-b9afc1ff3656@quic… Ackerley Tng (37): mm: hugetlb: Simplify logic in dequeue_hugetlb_folio_vma() mm: hugetlb: Refactor vma_has_reserves() to should_use_hstate_resv() mm: hugetlb: Remove unnecessary check for avoid_reserve mm: mempolicy: Refactor out policy_node_nodemask() mm: hugetlb: Refactor alloc_buddy_hugetlb_folio_with_mpol() to interpret mempolicy instead of vma mm: hugetlb: Refactor dequeue_hugetlb_folio_vma() to use mpol mm: hugetlb: Refactor out hugetlb_alloc_folio mm: truncate: Expose preparation steps for truncate_inode_pages_final mm: hugetlb: Expose hugetlb_subpool_{get,put}_pages() mm: hugetlb: Add option to create new subpool without using surplus mm: hugetlb: Expose hugetlb_acct_memory() mm: hugetlb: Move and expose hugetlb_zero_partial_page() KVM: guest_memfd: Make guest mem use guest mem inodes instead of anonymous inodes KVM: guest_memfd: hugetlb: initialization and cleanup KVM: guest_memfd: hugetlb: allocate and truncate from hugetlb KVM: guest_memfd: Add page alignment check for hugetlb guest_memfd KVM: selftests: Add basic selftests for hugetlb-backed guest_memfd KVM: selftests: Support various types of backing sources for private memory KVM: selftests: Update test for various private memory backing source types KVM: selftests: Add private_mem_conversions_test.sh KVM: selftests: Test that guest_memfd usage is reported via hugetlb mm: hugetlb: Expose vmemmap optimization functions mm: hugetlb: Expose HugeTLB functions for promoting/demoting pages mm: hugetlb: Add functions to add/move/remove from hugetlb lists KVM: guest_memfd: Track faultability within a struct kvm_gmem_private KVM: guest_memfd: Allow mmapping guest_memfd files KVM: guest_memfd: Use vm_type to determine default faultability KVM: Handle conversions in the SET_MEMORY_ATTRIBUTES ioctl KVM: guest_memfd: Handle folio preparation for guest_memfd mmap KVM: selftests: Allow vm_set_memory_attributes to be used without asserting return value of 0 KVM: selftests: Test using guest_memfd memory from userspace KVM: selftests: Test guest_memfd memory sharing between guest and host KVM: selftests: Add notes in private_mem_kvm_exits_test for mmap-able guest_memfd KVM: selftests: Test that pinned pages block KVM from setting memory attributes to PRIVATE KVM: selftests: Refactor vm_mem_add to be more flexible KVM: selftests: Add helper to perform madvise by memslots KVM: selftests: Update private_mem_conversions_test for mmap()able guest_memfd Vishal Annapurve (2): KVM: guest_memfd: Split HugeTLB pages for guest_memfd use KVM: guest_memfd: Dynamically split/reconstruct HugeTLB page fs/hugetlbfs/inode.c | 35 +- include/linux/hugetlb.h | 54 +- include/linux/kvm_host.h | 1 + include/linux/mempolicy.h | 2 + include/linux/mm.h | 1 + include/uapi/linux/kvm.h | 26 + include/uapi/linux/magic.h | 1 + mm/hugetlb.c | 346 ++-- mm/hugetlb_vmemmap.h | 11 - mm/mempolicy.c | 36 +- mm/truncate.c | 26 +- tools/include/linux/kernel.h | 4 +- tools/testing/selftests/kvm/Makefile | 3 + .../kvm/guest_memfd_hugetlb_reporting_test.c | 222 +++ .../selftests/kvm/guest_memfd_pin_test.c | 104 ++ .../selftests/kvm/guest_memfd_sharing_test.c | 160 ++ .../testing/selftests/kvm/guest_memfd_test.c | 238 ++- .../testing/selftests/kvm/include/kvm_util.h | 45 +- .../testing/selftests/kvm/include/test_util.h | 18 + tools/testing/selftests/kvm/lib/kvm_util.c | 443 +++-- tools/testing/selftests/kvm/lib/test_util.c | 99 ++ .../kvm/x86_64/private_mem_conversions_test.c | 158 +- .../x86_64/private_mem_conversions_test.sh | 91 + .../kvm/x86_64/private_mem_kvm_exits_test.c | 11 +- virt/kvm/guest_memfd.c | 1563 ++++++++++++++++- virt/kvm/kvm_main.c | 17 + virt/kvm/kvm_mm.h | 16 + 27 files changed, 3288 insertions(+), 443 deletions(-) create mode 100644 tools/testing/selftests/kvm/guest_memfd_hugetlb_reporting_test.c create mode 100644 tools/testing/selftests/kvm/guest_memfd_pin_test.c create mode 100644 tools/testing/selftests/kvm/guest_memfd_sharing_test.c create mode 100755 tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.sh -- 2.46.0.598.g6f2099f65c-goog

14 hours, 54 minutes

17
124
0 0

[PATCH v4 00/14] Add support for suppressing warning backtraces

by Alessandro Carminati

Some unit tests intentionally trigger warning backtraces by passing bad parameters to kernel API functions. Such unit tests typically check the return value from such calls, not the existence of the warning backtrace. Such intentionally generated warning backtraces are neither desirable nor useful for a number of reasons. - They can result in overlooked real problems. - A warning that suddenly starts to show up in unit tests needs to be investigated and has to be marked to be ignored, for example by adjusting filter scripts. Such filters are ad-hoc because there is no real standard format for warnings. On top of that, such filter scripts would require constant maintenance. One option to address problem would be to add messages such as "expected warning backtraces start / end here" to the kernel log. However, that would again require filter scripts, it might result in missing real problematic warning backtraces triggered while the test is running, and the irrelevant backtrace(s) would still clog the kernel log. Solve the problem by providing a means to identify and suppress specific warning backtraces while executing test code. Support suppressing multiple backtraces while at the same time limiting changes to generic code to the absolute minimum. Architecture specific changes are kept at minimum by retaining function names only if both CONFIG_DEBUG_BUGVERBOSE and CONFIG_KUNIT are enabled. The first patch of the series introduces the necessary infrastructure. The second patch introduces support for counting suppressed backtraces. This capability is used in patch three to implement unit tests. Patch four documents the new API. The next two patches add support for suppressing backtraces in drm_rect and dev_addr_lists unit tests. These patches are intended to serve as examples for the use of the functionality introduced with this series. The remaining patches implement the necessary changes for all architectures with GENERIC_BUG support. With CONFIG_KUNIT enabled, image size increase with this series applied is approximately 1%. The image size increase (and with it the functionality introduced by this series) can be avoided by disabling CONFIG_KUNIT_SUPPRESS_BACKTRACE. This series is based on the RFC patch and subsequent discussion at https://patchwork.kernel.org/project/linux-kselftest/patch/02546e59-1afe-4b… and offers a more comprehensive solution of the problem discussed there. Design note: Function pointers are only added to the __bug_table section if both CONFIG_KUNIT_SUPPRESS_BACKTRACE and CONFIG_DEBUG_BUGVERBOSE are enabled to avoid image size increases if CONFIG_KUNIT is disabled. There would be some benefits to adding those pointers all the time (reduced complexity, ability to display function names in BUG/WARNING messages). That change, if desired, can be made later. Checkpatch note: Remaining checkpatch errors and warnings were deliberately ignored. Some are triggered by matching coding style or by comments interpreted as code, others by assembler macros which are disliked by checkpatch. Suggestions for improvements are welcome. Changes since RFC: - Introduced CONFIG_KUNIT_SUPPRESS_BACKTRACE - Minor cleanups and bug fixes - Added support for all affected architectures - Added support for counting suppressed warnings - Added unit tests using those counters - Added patch to suppress warning backtraces in dev_addr_lists tests Changes since v1: - Rebased to v6.9-rc1 - Added Tested-by:, Acked-by:, and Reviewed-by: tags [I retained those tags since there have been no functional changes] - Introduced KUNIT_SUPPRESS_BACKTRACE configuration option, enabled by default. Changes since v2: - Rebased to v6.9-rc2 - Added comments to drm warning suppression explaining why it is needed. - Added patch to move conditional code in arch/sh/include/asm/bug.h to avoid kerneldoc warning - Added architecture maintainers to Cc: for architecture specific patches - No functional changes Changes since v3: - Rebased to v6.14-rc6 - Dropped net: "kunit: Suppress lock warning noise at end of dev_addr_lists tests" since 3db3b62955cd6d73afde05a17d7e8e106695c3b9 - Added __kunit_ and KUNIT_ prefixes. - Tested on interessed architectures. ---- Guenter Roeck (14): bug/kunit: Core support for suppressing warning backtraces kunit: bug: Count suppressed warning backtraces kunit: Add test cases for backtrace warning suppression kunit: Add documentation for warning backtrace suppression API drm: Suppress intentional warning backtraces in scaling unit tests x86: Add support for suppressing warning backtraces arm64: Add support for suppressing warning backtraces loongarch: Add support for suppressing warning backtraces parisc: Add support for suppressing warning backtraces s390: Add support for suppressing warning backtraces sh: Add support for suppressing warning backtraces sh: Move defines needed for suppressing warning backtraces riscv: Add support for suppressing warning backtraces powerpc: Add support for suppressing warning backtraces Documentation/dev-tools/kunit/usage.rst | 30 ++++++- arch/arm64/include/asm/asm-bug.h | 27 ++++-- arch/arm64/include/asm/bug.h | 8 +- arch/loongarch/include/asm/bug.h | 42 +++++++--- arch/parisc/include/asm/bug.h | 29 +++++-- arch/powerpc/include/asm/bug.h | 37 +++++++-- arch/riscv/include/asm/bug.h | 38 ++++++--- arch/s390/include/asm/bug.h | 17 +++- arch/sh/include/asm/bug.h | 28 ++++++- arch/x86/include/asm/bug.h | 21 +++-- drivers/gpu/drm/tests/drm_rect_test.c | 16 ++++ include/asm-generic/bug.h | 16 +++- include/kunit/bug.h | 56 +++++++++++++ include/kunit/test.h | 1 + include/linux/bug.h | 13 +++ lib/bug.c | 51 +++++++++++- lib/kunit/Kconfig | 9 ++ lib/kunit/Makefile | 7 +- lib/kunit/backtrace-suppression-test.c | 104 ++++++++++++++++++++++++ lib/kunit/bug.c | 42 ++++++++++ 20 files changed, 519 insertions(+), 73 deletions(-) create mode 100644 include/kunit/bug.h create mode 100644 lib/kunit/backtrace-suppression-test.c create mode 100644 lib/kunit/bug.c -- 2.34.1

3 days, 7 hours

15
44
0 0

[PATCH v12 00/28] riscv control-flow integrity for usermode

by Deepak Gupta

Basics and overview =================== Software with larger attack surfaces (e.g. network facing apps like databases, browsers or apps relying on browser runtimes) suffer from memory corruption issues which can be utilized by attackers to bend control flow of the program to eventually gain control (by making their payload executable). Attackers are able to perform such attacks by leveraging call-sites which rely on indirect calls or return sites which rely on obtaining return address from stack memory. To mitigate such attacks, risc-v extension zicfilp enforces that all indirect calls must land on a landing pad instruction `lpad` else cpu will raise software check exception (a new cpu exception cause code on riscv). Similarly for return flow, risc-v extension zicfiss extends architecture with - `sspush` instruction to push return address on a shadow stack - `sspopchk` instruction to pop return address from shadow stack and compare with input operand (i.e. return address on stack) - `sspopchk` to raise software check exception if comparision above was a mismatch - Protection mechanism using which shadow stack is not writeable via regular store instructions More information an details can be found at extensions github repo [1]. Equivalent to landing pad (zicfilp) on x86 is `ENDBRANCH` instruction in Intel CET [3] and branch target identification (BTI) [4] on arm. Similarly x86's Intel CET has shadow stack [5] and arm64 has guarded control stack (GCS) [6] which are very similar to risc-v's zicfiss shadow stack. x86 and arm64 support for user mode shadow stack is already in mainline. Kernel awareness for user control flow integrity ================================================ This series picks up Samuel Holland's envcfg changes [2] as well. So if those are being applied independently, they should be removed from this series. Enabling: In order to maintain compatibility and not break anything in user mode, kernel doesn't enable control flow integrity cpu extensions on binary by default. Instead exposes a prctl interface to enable, disable and lock the shadow stack or landing pad feature for a task. This allows userspace (loader) to enumerate if all objects in its address space are compiled with shadow stack and landing pad support and accordingly enable the feature. Additionally if a subsequent `dlopen` happens on a library, user mode can take a decision again to disable the feature (if incoming library is not compiled with support) OR terminate the task (if user mode policy is strict to have all objects in address space to be compiled with control flow integirty cpu feature). prctl to enable shadow stack results in allocating shadow stack from virtual memory and activating for user address space. x86 and arm64 are also following same direction due to similar reason(s). clone/fork: On clone and fork, cfi state for task is inherited by child. Shadow stack is part of virtual memory and is a writeable memory from kernel perspective (writeable via a restricted set of instructions aka shadow stack instructions) Thus kernel changes ensure that this memory is converted into read-only when fork/clone happens and COWed when fault is taken due to sspush, sspopchk or ssamoswap. In case `CLONE_VM` is specified and shadow stack is to be enabled, kernel will automatically allocate a shadow stack for that clone call. map_shadow_stack: x86 introduced `map_shadow_stack` system call to allow user space to explicitly map shadow stack memory in its address space. It is useful to allocate shadow for different contexts managed by a single thread (green threads or contexts) risc-v implements this system call as well. signal management: If shadow stack is enabled for a task, kernel performs an asynchronous control flow diversion to deliver the signal and eventually expects userspace to issue sigreturn so that original execution can be resumed. Even though resume context is prepared by kernel, it is in user space memory and is subject to memory corruption and corruption bugs can be utilized by attacker in this race window to perform arbitrary sigreturn and eventually bypass cfi mechanism. Another issue is how to ensure that cfi related state on sigcontext area is not trampled by legacy apps or apps compiled with old kernel headers. In order to mitigate control-flow hijacting, kernel prepares a token and place it on shadow stack before signal delivery and places address of token in sigcontext structure. During sigreturn, kernel obtains address of token from sigcontext struture, reads token from shadow stack and validates it and only then allow sigreturn to succeed. Compatiblity issue is solved by adopting dynamic sigcontext management introduced for vector extension. This series re-factor the code little bit to allow future sigcontext management easy (as proposed by Andy Chiu from SiFive) config and compilation: Introduce a new risc-v config option `CONFIG_RISCV_USER_CFI`. Selecting this config option picks the kernel support for user control flow integrity. This optin is presented only if toolchain has shadow stack and landing pad support. And is on purpose guarded by toolchain support. Reason being that eventually vDSO also needs to be compiled in with shadow stack and landing pad support. vDSO compile patches are not included as of now because landing pad labeling scheme is yet to settle for usermode runtime. To get more information on kernel interactions with respect to zicfilp and zicfiss, patch series adds documentation for `zicfilp` and `zicfiss` in following: Documentation/arch/riscv/zicfiss.rst Documentation/arch/riscv/zicfilp.rst How to test this series ======================= Toolchain --------- $ git clone git@github.com:sifive/riscv-gnu-toolchain.git -b cfi-dev $ riscv-gnu-toolchain/configure --prefix=<path-to-where-to-build> --with-arch=rv64gc_zicfilp_zicfiss --enable-linux --disable-gdb --with-extra-multilib-test="rv64gc_zicfilp_zicfiss-lp64d:-static" $ make -j$(nproc) Qemu ---- Get the lastest qemu $ cd qemu $ mkdir build $ cd build $ ../configure --target-list=riscv64-softmmu $ make -j$(nproc) Opensbi ------- $ git clone git@github.com:deepak0414/opensbi.git -b v6_cfi_spec_split_opensbi $ make CROSS_COMPILE=<your riscv toolchain> -j$(nproc) PLATFORM=generic Linux ----- Running defconfig is fine. CFI is enabled by default if the toolchain supports it. $ make ARCH=riscv CROSS_COMPILE=<path-to-cfi-riscv-gnu-toolchain>/build/bin/riscv64-unknown-linux-gnu- -j$(nproc) defconfig $ make ARCH=riscv CROSS_COMPILE=<path-to-cfi-riscv-gnu-toolchain>/build/bin/riscv64-unknown-linux-gnu- -j$(nproc) In case you're building your own rootfs using toolchain, please make sure you pick following patch to ensure that vDSO compiled with lpad and shadow stack. "arch/riscv: compile vdso with landing pad" Branch where above patch can be picked https://github.com/deepak0414/linux-riscv-cfi/tree/vdso_user_cfi_v6.12-rc1 Running ------- Modify your qemu command to have: -bios <path-to-cfi-opensbi>/build/platform/generic/firmware/fw_dynamic.bin -cpu rv64,zicfilp=true,zicfiss=true,zimop=true,zcmop=true vDSO related Opens (in the flux) ================================= I am listing these opens for laying out plan and what to expect in future patch sets. And of course for the sake of discussion. Shadow stack and landing pad enabling in vDSO ---------------------------------------------- vDSO must have shadow stack and landing pad support compiled in for task to have shadow stack and landing pad support. This patch series doesn't enable that (yet). Enabling shadow stack support in vDSO should be straight forward (intend to do that in next versions of patch set). Enabling landing pad support in vDSO requires some collaboration with toolchain folks to follow a single label scheme for all object binaries. This is necessary to ensure that all indirect call-sites are setting correct label and target landing pads are decorated with same label scheme. How many vDSOs --------------- Shadow stack instructions are carved out of zimop (may be operations) and if CPU doesn't implement zimop, they're illegal instructions. Kernel could be running on a CPU which may or may not implement zimop. And thus kernel will have to carry 2 different vDSOs and expose the appropriate one depending on whether CPU implements zimop or not. References ========== [1] - https://github.com/riscv/riscv-cfi [2] - https://lore.kernel.org/all/20240814081126.956287-1-samuel.holland@sifive.c… [3] - https://lwn.net/Articles/889475/ [4] - https://developer.arm.com/documentation/109576/0100/Branch-Target-Identific… [5] - https://www.intel.com/content/dam/develop/external/us/en/documents/catc17-i… [6] - https://lwn.net/Articles/940403/ --- changelog --------- v12: - It seems like I had accidently squashed arch agnostic indirect branch tracking prctl and riscv implementation of those prctls. Split them again. - set_shstk_status/set_indir_lp_status perform CSR writes only when CPU support is available. As suggested by Zong Li. - Some minor clean up in kselftests as suggested by Zong Li. v11: - patch "arch/riscv: compile vdso with landing pad" was unconditionally selecting `_zicfilp` for vDSO compile. fixed that. Changed `lpad 1` to to `lpad 0`. v10: - dropped "mm: helper `is_shadow_stack_vma` to check shadow stack vma". This patch is not that interesting to this patch series for risc-v. There are instances in arch directories where VM_SHADOW_STACK flag is anyways used. Dropping this patch to expedite merging in riscv tree. - Took suggestions from `Clement` on "riscv: zicfiss / zicfilp enumeration" to validate presence of cfi based on config. - Added a patch for vDSO to have `lpad 0`. I had omitted this earlier to make sure we add single vdso object with cfi enabled. But a vdso object with scheme of zero labeled landing pad is least common denominator and should work with all objects of zero labeled as well as function-signature labeled objects. v9: - rebased on master (39a803b754d5 fix braino in "9p: fix ->rename_sem exclusion") - dropped "mm: Introduce ARCH_HAS_USER_SHADOW_STACK" (master has it from arm64/gcs) - dropped "prctl: arch-agnostic prctl for shadow stack" (master has it from arm64/gcs) v8: - rebased on palmer/for-next - dropped samuel holland's `envcfg` context switch patches. they are in parlmer/for-next v7: - Removed "riscv/Kconfig: enable HAVE_EXIT_THREAD for riscv" Instead using `deactivate_mm` flow to clean up. see here for more context https://lore.kernel.org/all/20230908203655.543765-1-rick.p.edgecombe@intel.… - Changed the header include in `kselftest`. Hopefully this fixes compile issue faced by Zong Li at SiFive. - Cleaned up an orphaned change to `mm/mmap.c` in below patch "riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE" - Lock interfaces for shadow stack and indirect branch tracking expect arg == 0 Any future evolution of this interface should accordingly define how arg should be setup. - `mm/map.c` has an instance of using `VM_SHADOW_STACK`. Fixed it to use helper `is_shadow_stack_vma`. - Link to v6: https://lore.kernel.org/r/20241008-v5_user_cfi_series-v6-0-60d9fe073f37@riv… v6: - Picked up Samuel Holland's changes as is with `envcfg` placed in `thread` instead of `thread_info` - fixed unaligned newline escapes in kselftest - cleaned up messages in kselftest and included test output in commit message - fixed a bug in clone path reported by Zong Li - fixed a build issue if CONFIG_RISCV_ISA_V is not selected (this was introduced due to re-factoring signal context management code) v5: - rebased on v6.12-rc1 - Fixed schema related issues in device tree file - Fixed some of the documentation related issues in zicfilp/ss.rst (style issues and added index) - added `SHADOW_STACK_SET_MARKER` so that implementation can define base of shadow stack. - Fixed warnings on definitions added in usercfi.h when CONFIG_RISCV_USER_CFI is not selected. - Adopted context header based signal handling as proposed by Andy Chiu - Added support for enabling kernel mode access to shadow stack using FWFT (https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/src/ext-firmware…) - Link to v5: https://lore.kernel.org/r/20241001-v5_user_cfi_series-v1-0-3ba65b6e550f@riv… (Note: I had an issue in my workflow due to which version number wasn't picked up correctly while sending out patches) v4: - rebased on 6.11-rc6 - envcfg: Converged with Samuel Holland's patches for envcfg management on per- thread basis. - vma_is_shadow_stack is renamed to is_vma_shadow_stack - picked up Mark Brown's `ARCH_HAS_USER_SHADOW_STACK` patch - signal context: using extended context management to maintain compatibility. - fixed `-Wmissing-prototypes` compiler warnings for prctl functions - Documentation fixes and amending typos. - Link to v4: https://lore.kernel.org/all/20240912231650.3740732-1-debug@rivosinc.com/ v3: - envcfg logic to pick up base envcfg had a bug where `ENVCFG_CBZE` could have been picked on per task basis, even though CPU didn't implement it. Fixed in this series. - dt-bindings As suggested, split into separate commit. fixed the messaging that spec is in public review - arch_is_shadow_stack change arch_is_shadow_stack changed to vma_is_shadow_stack - hwprobe zicfiss / zicfilp if present will get enumerated in hwprobe - selftests As suggested, added object and binary filenames to .gitignore Selftest binary anyways need to be compiled with cfi enabled compiler which will make sure that landing pad and shadow stack are enabled. Thus removed separate enable/disable tests. Cleaned up tests a bit. - Link to v3: https://lore.kernel.org/lkml/20240403234054.2020347-1-debug@rivosinc.com/ v2: - Using config `CONFIG_RISCV_USER_CFI`, kernel support for riscv control flow integrity for user mode programs can be compiled in the kernel. - Enabling of control flow integrity for user programs is left to user runtime - This patch series introduces arch agnostic `prctls` to enable shadow stack and indirect branch tracking. And implements them on riscv. --- --- Changes in v12: - EDITME: describe what is new in this series revision. - EDITME: use bulletpoints and terse descriptions. - Link to v11: https://lore.kernel.org/r/20250310-v5_user_cfi_series-v11-0-86b36cbfb910@ri… Changes in v11: - EDITME: describe what is new in this series revision. - EDITME: use bulletpoints and terse descriptions. - Link to v10: https://lore.kernel.org/r/20250210-v5_user_cfi_series-v10-0-163dcfa31c60@ri… --- Andy Chiu (1): riscv: signal: abstract header saving for setup_sigcontext Clément Léger (1): riscv: Add Firmware Feature SBI extensions definitions Deepak Gupta (25): mm: VM_SHADOW_STACK definition for riscv dt-bindings: riscv: zicfilp and zicfiss in dt-bindings (extensions.yaml) riscv: zicfiss / zicfilp enumeration riscv: zicfiss / zicfilp extension csr and bit definitions riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE riscv mm: manufacture shadow stack pte riscv mmu: teach pte_mkwrite to manufacture shadow stack PTEs riscv mmu: write protect and shadow stack riscv/mm: Implement map_shadow_stack() syscall riscv/shstk: If needed allocate a new shadow stack on clone riscv: Implements arch agnostic shadow stack prctls prctl: arch-agnostic prctl for indirect branch tracking riscv: Implements arch agnostic indirect branch tracking prctls riscv/traps: Introduce software check exception riscv/signal: save and restore of shadow stack for signal riscv/kernel: update __show_regs to print shadow stack register riscv/ptrace: riscv cfi status and state via ptrace and in core files riscv/hwprobe: zicfilp / zicfiss enumeration in hwprobe riscv: enable kernel access to shadow stack memory via FWFT sbi call riscv: kernel command line option to opt out of user cfi riscv: create a config for shadow stack and landing pad instr support riscv: Documentation for landing pad / indirect branch tracking riscv: Documentation for shadow stack on riscv kselftest/riscv: kselftest for user mode cfi Jim Shu (1): arch/riscv: compile vdso with landing pad Documentation/arch/riscv/index.rst | 2 + Documentation/arch/riscv/zicfilp.rst | 115 +++++ Documentation/arch/riscv/zicfiss.rst | 176 +++++++ .../devicetree/bindings/riscv/extensions.yaml | 14 + arch/riscv/Kconfig | 20 + arch/riscv/Makefile | 5 +- arch/riscv/include/asm/asm-prototypes.h | 1 + arch/riscv/include/asm/assembler.h | 44 ++ arch/riscv/include/asm/cpufeature.h | 13 + arch/riscv/include/asm/csr.h | 16 + arch/riscv/include/asm/entry-common.h | 2 + arch/riscv/include/asm/hwcap.h | 2 + arch/riscv/include/asm/mman.h | 25 + arch/riscv/include/asm/mmu_context.h | 7 + arch/riscv/include/asm/pgtable.h | 30 +- arch/riscv/include/asm/processor.h | 2 + arch/riscv/include/asm/sbi.h | 26 + arch/riscv/include/asm/thread_info.h | 3 + arch/riscv/include/asm/usercfi.h | 89 ++++ arch/riscv/include/asm/vector.h | 3 + arch/riscv/include/uapi/asm/hwprobe.h | 2 + arch/riscv/include/uapi/asm/ptrace.h | 22 + arch/riscv/include/uapi/asm/sigcontext.h | 1 + arch/riscv/kernel/Makefile | 1 + arch/riscv/kernel/asm-offsets.c | 8 + arch/riscv/kernel/cpufeature.c | 13 + arch/riscv/kernel/entry.S | 31 +- arch/riscv/kernel/head.S | 12 + arch/riscv/kernel/process.c | 26 +- arch/riscv/kernel/ptrace.c | 83 ++++ arch/riscv/kernel/signal.c | 142 +++++- arch/riscv/kernel/sys_hwprobe.c | 2 + arch/riscv/kernel/sys_riscv.c | 10 + arch/riscv/kernel/traps.c | 43 ++ arch/riscv/kernel/usercfi.c | 530 +++++++++++++++++++++ arch/riscv/kernel/vdso/Makefile | 12 + arch/riscv/kernel/vdso/flush_icache.S | 4 + arch/riscv/kernel/vdso/getcpu.S | 4 + arch/riscv/kernel/vdso/rt_sigreturn.S | 4 + arch/riscv/kernel/vdso/sys_hwprobe.S | 4 + arch/riscv/mm/init.c | 2 +- arch/riscv/mm/pgtable.c | 17 + include/linux/cpu.h | 4 + include/linux/mm.h | 7 + include/uapi/linux/elf.h | 1 + include/uapi/linux/prctl.h | 27 ++ kernel/sys.c | 30 ++ tools/testing/selftests/riscv/Makefile | 2 +- tools/testing/selftests/riscv/cfi/.gitignore | 3 + tools/testing/selftests/riscv/cfi/Makefile | 10 + tools/testing/selftests/riscv/cfi/cfi_rv_test.h | 82 ++++ tools/testing/selftests/riscv/cfi/riscv_cfi_test.c | 78 +++ tools/testing/selftests/riscv/cfi/shadowstack.c | 385 +++++++++++++++ tools/testing/selftests/riscv/cfi/shadowstack.h | 27 ++ 54 files changed, 2195 insertions(+), 29 deletions(-) --- base-commit: 39a803b754d5224a3522016b564113ee1e4091b2 change-id: 20240930-v5_user_cfi_series-3dc332f8f5b2 -- - debug

3 days, 17 hours

5
82
0 0

[PATCH v4 00/38] Mediated vPMU 4.0 for x86

by Mingwei Zhang

With joint effort from the upstream KVM community, we come up with the 4th version of mediated vPMU for x86. We have made the following changes on top of the previous RFC v3. v3 -> v4 - Rebase whole patchset on 6.14-rc3 base. - Address Peter's comments on Perf part. - Address Sean's comments on KVM part. * Change key word "passthrough" to "mediated" in all patches * Change static enabling to user space dynamic enabling via KVM_CAP_PMU_CAPABILITY. * Only support GLOBAL_CTRL save/restore with VMCS exec_ctrl, drop the MSR save/retore list support for GLOBAL_CTRL, thus the support of mediated vPMU is constrained to SapphireRapids and later CPUs on Intel side. * Merge some small changes into a single patch. - Address Sandipan's comment on invalid pmu pointer. - Add back "eventsel_hw" and "fixed_ctr_ctrl_hw" to avoid to directly manipulate pmc->eventsel and pmu->fixed_ctr_ctrl. Testing (Intel side): - Perf-based legacy vPMU (force emulation on/off) * Kselftests pmu_counters_test, pmu_event_filter_test and vmx_pmu_caps_test pass. * KUT PMU tests pmu, pmu_lbr, pmu_pebs pass. * Basic perf counting/sampling tests in 3 scenarios, guest-only, host-only and host-guest coexistence all pass. - Mediated vPMU (force emulation on/off) * Kselftests pmu_counters_test, pmu_event_filter_test and vmx_pmu_caps_test pass. * KUT PMU tests pmu, pmu_lbr, pmu_pebs pass. * Basic perf counting/sampling tests in 3 scenarios, guest-only, host-only and host-guest coexistence all pass. - Failures. All above tests passed on Intel Granite Rapids as well except a failure on KUT/pmu_pebs. * GP counter 0 (0xfffffffffffe): PEBS record (written seq 0) is verified (including size, counters and cfg). * The pebs_data_cfg (0xb500000000) doesn't match with the effective MSR_PEBS_DATA_CFG (0x0). * This failure has nothing to do with this mediated vPMU patch set. The failure is caused by Granite Rapids supported timed PEBS which needs extra support on Qemu and KUT/pmu_pebs. These extra support would be sent in separate patches later. Testing (AMD side): - Kselftests pmu_counters_test, pmu_event_filter_test and vmx_pmu_caps_test all pass - legacy guest with KUT/pmu: * qmeu option: -cpu host, -perfctr-core * when set force_emulation_prefix=1, passes * when set force_emulation_prefix=0, passes - perfmon-v1 guest with KUT/pmu: * qmeu option: -cpu host, -perfmon-v2 * when set force_emulation_prefix=1, passes * when set force_emulation_prefix=0, passes - perfmon-v2 guest with KUT/pmu: * qmeu option: -cpu host * when set force_emulation_prefix=1, passes * when set force_emulation_prefix=0, passes - perf_fuzzer (perfmon-v2): * fails with soft lockup in guest in current version. * culprit could be between 6.13 ~ 6.14-rc3 within KVM * Series tested on 6.12 and 6.13 without issue. Note: a QEMU series is needed to run mediated vPMU v4: - https://lore.kernel.org/all/20250324123712.34096-1-dapeng1.mi@linux.intel.c… History: - RFC v3: https://lore.kernel.org/all/20240801045907.4010984-1-mizhang@google.com/ - RFC v2: https://lore.kernel.org/all/20240506053020.3911940-1-mizhang@google.com/ - RFC v1: https://lore.kernel.org/all/20240126085444.324918-1-xiong.y.zhang@linux.int… Dapeng Mi (18): KVM: x86/pmu: Introduce enable_mediated_pmu global parameter KVM: x86/pmu: Check PMU cpuid configuration from user space KVM: x86: Rename vmx_vmentry/vmexit_ctrl() helpers KVM: x86/pmu: Add perf_capabilities field in struct kvm_host_values{} KVM: x86/pmu: Move PMU_CAP_{FW_WRITES,LBR_FMT} into msr-index.h header KVM: VMX: Add macros to wrap around {secondary,tertiary}_exec_controls_changebit() KVM: x86/pmu: Check if mediated vPMU can intercept rdpmc KVM: x86/pmu/vmx: Save/load guest IA32_PERF_GLOBAL_CTRL with vm_exit/entry_ctrl KVM: x86/pmu: Optimize intel/amd_pmu_refresh() helpers KVM: x86/pmu: Setup PMU MSRs' interception mode KVM: x86/pmu: Handle PMU MSRs interception and event filtering KVM: x86/pmu: Switch host/guest PMU context at vm-exit/vm-entry KVM: x86/pmu: Handle emulated instruction for mediated vPMU KVM: nVMX: Add macros to simplify nested MSR interception setting KVM: selftests: Add mediated vPMU supported for pmu tests KVM: Selftests: Support mediated vPMU for vmx_pmu_caps_test KVM: Selftests: Fix pmu_counters_test error for mediated vPMU KVM: x86/pmu: Expose enable_mediated_pmu parameter to user space Kan Liang (8): perf: Support get/put mediated PMU interfaces perf: Skip pmu_ctx based on event_type perf: Clean up perf ctx time perf: Add a EVENT_GUEST flag perf: Add generic exclude_guest support perf: Add switch_guest_ctx() interface perf/x86: Support switch_guest_ctx interface perf/x86/intel: Support PERF_PMU_CAP_MEDIATED_VPMU Mingwei Zhang (5): perf/x86: Forbid PMI handler when guest own PMU perf/x86/core: Plumb mediated PMU capability from x86_pmu to x86_pmu_cap KVM: x86/pmu: Exclude PMU MSRs in vmx_get_passthrough_msr_slot() KVM: x86/pmu: introduce eventsel_hw to prepare for pmu event filtering KVM: nVMX: Add nested virtualization support for mediated PMU Sandipan Das (4): perf/x86/core: Do not set bit width for unavailable counters KVM: x86/pmu: Add AMD PMU registers to direct access list KVM: x86/pmu/svm: Set GuestOnly bit and clear HostOnly bit when guest write to event selectors perf/x86/amd: Support PERF_PMU_CAP_MEDIATED_VPMU for AMD host Xiong Zhang (3): x86/irq: Factor out common code for installing kvm irq handler perf: core/x86: Register a new vector for KVM GUEST PMI KVM: x86/pmu: Register KVM_GUEST_PMI_VECTOR handler arch/x86/events/amd/core.c | 2 + arch/x86/events/core.c | 40 +- arch/x86/events/intel/core.c | 5 + arch/x86/include/asm/hardirq.h | 1 + arch/x86/include/asm/idtentry.h | 1 + arch/x86/include/asm/irq.h | 2 +- arch/x86/include/asm/irq_vectors.h | 5 +- arch/x86/include/asm/kvm-x86-pmu-ops.h | 2 + arch/x86/include/asm/kvm_host.h | 10 + arch/x86/include/asm/msr-index.h | 18 +- arch/x86/include/asm/perf_event.h | 1 + arch/x86/include/asm/vmx.h | 1 + arch/x86/kernel/idt.c | 1 + arch/x86/kernel/irq.c | 39 +- arch/x86/kvm/cpuid.c | 15 + arch/x86/kvm/pmu.c | 254 ++++++++- arch/x86/kvm/pmu.h | 45 ++ arch/x86/kvm/svm/pmu.c | 148 ++++- arch/x86/kvm/svm/svm.c | 26 + arch/x86/kvm/svm/svm.h | 2 +- arch/x86/kvm/vmx/capabilities.h | 11 +- arch/x86/kvm/vmx/nested.c | 68 ++- arch/x86/kvm/vmx/pmu_intel.c | 224 ++++++-- arch/x86/kvm/vmx/vmx.c | 89 +-- arch/x86/kvm/vmx/vmx.h | 11 +- arch/x86/kvm/x86.c | 63 ++- arch/x86/kvm/x86.h | 2 + include/linux/perf_event.h | 47 +- kernel/events/core.c | 519 ++++++++++++++---- .../beauty/arch/x86/include/asm/irq_vectors.h | 5 +- .../selftests/kvm/include/kvm_test_harness.h | 13 + .../testing/selftests/kvm/include/kvm_util.h | 3 + .../selftests/kvm/include/x86/processor.h | 8 + tools/testing/selftests/kvm/lib/kvm_util.c | 23 + .../selftests/kvm/x86/pmu_counters_test.c | 24 +- .../selftests/kvm/x86/pmu_event_filter_test.c | 8 +- .../selftests/kvm/x86/vmx_pmu_caps_test.c | 2 +- 37 files changed, 1480 insertions(+), 258 deletions(-) base-commit: 0ad2507d5d93f39619fc42372c347d6006b64319 -- 2.49.0.395.g12beb8f557-goog

3 days, 20 hours

5
48
0 0

[PATCH] selftests/pidfd: align stack to fix SP alignment exception

by Shuai Xue

The pidfd_test fails on the ARM64 platform with the following error: Bail out! pidfd_poll check for premature notification on child thread exec test: Failed When exception-trace is enabled, the kernel logs the details: #echo 1 > /proc/sys/debug/exception-trace #dmesg | tail -n 20 [48628.713023] pidfd_test[1082142]: unhandled exception: SP Alignment, ESR 0x000000009a000000, SP/PC alignment exception in pidfd_test[400000+4000] [48628.713049] CPU: 21 PID: 1082142 Comm: pidfd_test Kdump: loaded Tainted: G W E 6.6.71-3_rc1.al8.aarch64 #1 [48628.713051] Hardware name: AlibabaCloud AliServer-Xuanwu2.0AM-1UC1P-5B/AS1111MG1, BIOS 1.2.M1.AL.P.157.00 07/29/2023 [48628.713053] pstate: 60001800 (nZCv daif -PAN -UAO -TCO -DIT +SSBS BTYPE=-c) [48628.713055] pc : 0000000000402100 [48628.713056] lr : 0000ffff98288f9c [48628.713056] sp : 0000ffffde49daa8 [48628.713057] x29: 0000000000000000 x28: 0000000000000000 x27: 0000000000000000 [48628.713060] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 [48628.713062] x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000400e80 [48628.713065] x20: 0000000000000000 x19: 0000000000402650 x18: 0000000000000000 [48628.713067] x17: 00000000004200d8 x16: 0000ffff98288f40 x15: 0000ffffde49b92c [48628.713070] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [48628.713072] x11: 0000000000001011 x10: 0000000000402100 x9 : 0000000000000010 [48628.713074] x8 : 00000000000000dc x7 : 3861616239346564 x6 : 000000000000000a [48628.713077] x5 : 0000ffffde49daa8 x4 : 000000000000000a x3 : 0000ffffde49daa8 [48628.713079] x2 : 0000ffffde49dadc x1 : 0000ffffde49daa8 x0 : 0000000000000000 According to ARM ARM D1.3.10.2 SP alignment checking: > When the SP is used as the base address of a calculation, regardless of > any offset applied by the instruction, if bits [3:0] of the SP are not > 0b0000, there is a misaligned SP. To fix it, align the stack with 16 bytes. Signed-off-by: Shuai Xue <xueshuai(a)linux.alibaba.com> --- tools/testing/selftests/pidfd/pidfd_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/pidfd/pidfd_test.c b/tools/testing/selftests/pidfd/pidfd_test.c index c081ae91313a..ec161a7c3ff9 100644 --- a/tools/testing/selftests/pidfd/pidfd_test.c +++ b/tools/testing/selftests/pidfd/pidfd_test.c @@ -33,7 +33,7 @@ static bool have_pidfd_send_signal; static pid_t pidfd_clone(int flags, int *pidfd, int (*fn)(void *)) { size_t stack_size = 1024; - char *stack[1024] = { 0 }; + char *stack[1024] __attribute__((aligned(16))) = {0}; #ifdef __ia64__ return __clone2(fn, stack, stack_size, flags | SIGCHLD, NULL, pidfd); -- 2.39.3

5 days, 3 hours

2
4
0 0

[PATCH v4 0/5] Add support for the Bus Lock Threshold

by Manali Shukla

Misbehaving guests can cause bus locks to degrade the performance of a system. Non-WB (write-back) and misaligned locked RMW (read-modify-write) instructions are referred to as "bus locks" and require system wide synchronization among all processors to guarantee the atomicity. The bus locks can impose notable performance penalties for all processors within the system. Support for the Bus Lock Threshold is indicated by CPUID Fn8000_000A_EDX[29] BusLockThreshold=1, the VMCB provides a Bus Lock Threshold enable bit and an unsigned 16-bit Bus Lock Threshold count. VMCB intercept bit VMCB Offset Bits Function 14h 5 Intercept bus lock operations Bus lock threshold count VMCB Offset Bits Function 120h 15:0 Bus lock counter During VMRUN, the bus lock threshold count is fetched and stored in an internal count register. Prior to executing a bus lock within the guest, the processor verifies the count in the bus lock register. If the count is greater than zero, the processor executes the bus lock, reducing the count. However, if the count is zero, the bus lock operation is not performed, and instead, a Bus Lock Threshold #VMEXIT is triggered to transfer control to the Virtual Machine Monitor (VMM). A Bus Lock Threshold #VMEXIT is reported to the VMM with VMEXIT code 0xA5h, VMEXIT_BUSLOCK. EXITINFO1 and EXITINFO2 are set to 0 on a VMEXIT_BUSLOCK. On a #VMEXIT, the processor writes the current value of the Bus Lock Threshold Counter to the VMCB. Note: Currently, virtualizing the Bus Lock Threshold feature for L1 guest is not supported. More details about the Bus Lock Threshold feature can be found in AMD APM [1]. v3 -> v4 - Incorporated Sean's review comments - Added a preparatory patch to move linear_rip out of kvm_pio_request, so that it can be used by the bus lock threshold patches. - Added complete_userspace_buslock() function to reload bus_lock_counter to '1' only if the usespace has not changed the RIP. - Added changes to continue running bus_lock_counter accross the nested transitions. v2 -> v3 - Drop parch to add virt tag in /proc/cpuinfo. - Incorporated Tom's review comments. v1 -> v2 - Incorporated misc review comments from Sean. - Removed bus_lock_counter module parameter. - Set the value of bus_lock_counter to zero by default and reload the value by 1 in bus lock exit handler. - Add documentation for the behavioral difference for KVM_EXIT_BUS_LOCK. - Improved selftest for buslock to work on SVM and VMX. - Rewrite the commit messages. Patches are prepared on kvm-next/next (c9ea48bb6ee6). Testing done: - Tested the Bus Lock Threshold functionality on normal, SEV, SEV-ES and SEV-SNP guests. - Tested the Bus Lock Threshold functionality on nested guests. v1: https://lore.kernel.org/kvm/20240709175145.9986-4-manali.shukla@amd.com/T/ v2: https://lore.kernel.org/kvm/20241001063413.687787-4-manali.shukla@amd.com/T/ v3: https://lore.kernel.org/kvm/20241004053341.5726-1-manali.shukla@amd.com/T/ [1]: AMD64 Architecture Programmer's Manual Pub. 24593, April 2024, Vol 2, 15.14.5 Bus Lock Threshold. https://bugzilla.kernel.org/attachment.cgi?id=306250 Manali Shukla (3): KVM: x86: Preparatory patch to move linear_rip out of kvm_pio_request x86/cpufeatures: Add CPUID feature bit for the Bus Lock Threshold KVM: SVM: Add support for KVM_CAP_X86_BUS_LOCK_EXIT on SVM CPUs Nikunj A Dadhania (2): KVM: SVM: Enable Bus lock threshold exit KVM: selftests: Add bus lock exit test Documentation/virt/kvm/api.rst | 19 +++ arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/include/asm/svm.h | 5 +- arch/x86/include/uapi/asm/svm.h | 2 + arch/x86/kvm/svm/nested.c | 42 ++++++ arch/x86/kvm/svm/svm.c | 38 +++++ arch/x86/kvm/svm/svm.h | 2 + arch/x86/kvm/x86.c | 8 +- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/x86/kvm_buslock_test.c | 135 ++++++++++++++++++ 11 files changed, 249 insertions(+), 6 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86/kvm_buslock_test.c base-commit: c9ea48bb6ee6b28bbc956c1e8af98044618fed5e -- 2.34.1

5 days, 18 hours

4
18
0 0

[PATCH v6 0/5] userfaultfd move option

by Suren Baghdasaryan

This patch series introduces UFFDIO_MOVE feature to userfaultfd, which has long been implemented and maintained by Andrea in his local tree [1], but was not upstreamed due to lack of use cases where this approach would be better than allocating a new page and copying the contents. Previous upstraming attempts could be found at [6] and [7]. UFFDIO_COPY performs ~20% better than UFFDIO_MOVE when the application needs pages to be allocated [2]. However, with UFFDIO_MOVE, if pages are available (in userspace) for recycling, as is usually the case in heap compaction algorithms, then we can avoid the page allocation and memcpy (done by UFFDIO_COPY). Also, since the pages are recycled in the userspace, we avoid the need to release (via madvise) the pages back to the kernel [3]. We see over 40% reduction (on a Google pixel 6 device) in the compacting thread’s completion time by using UFFDIO_MOVE vs. UFFDIO_COPY. This was measured using a benchmark that emulates a heap compaction implementation using userfaultfd (to allow concurrent accesses by application threads). More details of the usecase are explained in [3]. Furthermore, UFFDIO_MOVE enables moving swapped-out pages without touching them within the same vma. Today, it can only be done by mremap, however it forces splitting the vma. TODOs for follow-up improvements: - cross-mm support. Known differences from single-mm and missing pieces: - memcg recharging (might need to isolate pages in the process) - mm counters - cross-mm deposit table moves - cross-mm test - document the address space where src and dest reside in struct uffdio_move - TLB flush batching. Will require extensive changes to PTL locking in move_pages_pte(). OTOH that might let us reuse parts of mremap code. Changes since v5 [10]: - added logic to split large folios in move_pages_pte(), per David Hildenbrand - added check for PAE before split_huge_pmd() to avoid the split if the move operation can't be done - replaced calls to default_huge_page_size() with read_pmd_pagesize() in uffd_move_pmd test, per David Hildenbrand - fixed the condition in uffd_move_test_common() checking if area alignment is needed Changes since v4 [9]: - added Acked-by in patch 1, per Peter Xu - added description for ctx, mm and mode parameters of move_pages(), per kernel test robot - added Reviewed-by's, per Peter Xu and Axel Rasmussen - removed unused operations in uffd_test_case_ops - refactored uffd-unit-test changes to avoid using global variables and handle pmd moves without page size overrides, per Peter Xu Changes since v3 [8]: - changed retry path in folio_lock_anon_vma_read() to unlock and then relock RCU, per Peter Xu - removed cross-mm support from initial patchset, per David Hildenbrand - replaced BUG_ONs with VM_WARN_ON or WARN_ON_ONCE, per David Hildenbrand - added missing cache flushing, per Lokesh Gidra and Peter Xu - updated manpage text in the patch description, per Peter Xu - renamed internal functions from "remap" to "move", per Peter Xu - added mmap_changing check after taking mmap_lock, per Peter Xu - changed uffd context check to ensure dst_mm is registered onto uffd we are operating on, Peter Xu and David Hildenbrand - changed to non-maybe variants of maybe*_mkwrite(), per David Hildenbrand - fixed warning for CONFIG_TRANSPARENT_HUGEPAGE=n, per kernel test robot - comments cleanup, per David Hildenbrand and Peter Xu - checks for VM_IO,VM_PFNMAP,VM_HUGETLB,..., per David Hildenbrand - prevent moving pinned pages, per Peter Xu - changed uffd tests to call move uffd_test_ctx_clear() at the end of the test run instead of in the beginning of the next run - added support for testcase-specific ops - added test for moving PMD-aligned blocks Changes since v2 [5]: - renamed UFFDIO_REMAP to UFFDIO_MOVE, per David Hildenbrand - rebase over mm-unstable to use folio_move_anon_rmap(), per David Hildenbrand - added text for manpage explaining DONTFORK and KSM requirements for this feature, per David Hildenbrand - check for anon_vma changes in the fast path of folio_lock_anon_vma_read, per Peter Xu - updated the title and description of the first patch, per David Hildenbrand - updating comments in folio_lock_anon_vma_read() explaining the need for anon_vma checks, per David Hildenbrand - changed all mapcount checks to PageAnonExclusive, per Jann Horn and David Hildenbrand - changed counters in remap_swap_pte() from MM_ANONPAGES to MM_SWAPENTS, per Jann Horn - added a check for PTE change after folio is locked in remap_pages_pte(), per Jann Horn - added handling of PMD migration entries and bailout when pmd_devmap(), per Jann Horn - added checks to ensure both src and dst VMAs are writable, per Peter Xu - added UFFD_FEATURE_MOVE, per Peter Xu - removed obsolete comments, per Peter Xu - renamed remap_anon_pte to remap_present_pte, per Peter Xu - added a comment for folio_get_anon_vma() explaining the need for anon_vma checks, per Peter Xu - changed error handling in remap_pages() to make it more clear, per Peter Xu - changed EFAULT to EAGAIN to retry when a hugepage appears or disappears from under us, per Peter Xu - added links to previous upstreaming attempts, per David Hildenbrand Changes since v1 [4]: - add mmget_not_zero in userfaultfd_remap, per Jann Horn - removed extern from function definitions, per Matthew Wilcox - converted to folios in remap_pages_huge_pmd, per Matthew Wilcox - use PageAnonExclusive in remap_pages_huge_pmd, per David Hildenbrand - handle pgtable transfers between MMs, per Jann Horn - ignore concurrent A/D pte bit changes, per Jann Horn - split functions into smaller units, per David Hildenbrand - test for folio_test_large in remap_anon_pte, per Matthew Wilcox - use pte_swp_exclusive for swapcount check, per David Hildenbrand - eliminated use of mmu_notifier_invalidate_range_start_nonblock, per Jann Horn - simplified THP alignment checks, per Jann Horn - refactored the loop inside remap_pages, per Jann Horn - additional clarifying comments, per Jann Horn Main changes since Andrea's last version [1]: - Trivial translations from page to folio, mmap_sem to mmap_lock - Replace pmd_trans_unstable() with pte_offset_map_nolock() and handle its possible failure - Move pte mapping into remap_pages_pte to allow for retries when source page or anon_vma is contended. Since pte_offset_map_nolock() start RCU read section, we can't block anymore after mapping a pte, so have to unmap the ptesm do the locking and retry. - Add and use anon_vma_trylock_write() to avoid blocking while in RCU read section. - Accommodate changes in mmu_notifier_range_init() API, switch to mmu_notifier_invalidate_range_start_nonblock() to avoid blocking while in RCU read section. - Open-code now removed __swp_swapcount() - Replace pmd_read_atomic() with pmdp_get_lockless() - Add new selftest for UFFDIO_MOVE [1] https://gitlab.com/aarcange/aa/-/commit/2aec7aea56b10438a3881a20a411aa4b1fc… [2] https://lore.kernel.org/all/1425575884-2574-1-git-send-email-aarcange@redha… [3] https://lore.kernel.org/linux-mm/CA+EESO4uO84SSnBhArH4HvLNhaUQ5nZKNKXqxRCyj… [4] https://lore.kernel.org/all/20230914152620.2743033-1-surenb@google.com/ [5] https://lore.kernel.org/all/20230923013148.1390521-1-surenb@google.com/ [6] https://lore.kernel.org/all/1425575884-2574-21-git-send-email-aarcange@redh… [7] https://lore.kernel.org/all/cover.1547251023.git.blake.caldwell@colorado.ed… [8] https://lore.kernel.org/all/20231009064230.2952396-1-surenb@google.com/ [9] https://lore.kernel.org/all/20231028003819.652322-1-surenb@google.com/ [10] https://lore.kernel.org/all/20231121171643.3719880-1-surenb@google.com/ Andrea Arcangeli (2): mm/rmap: support move to different root anon_vma in folio_move_anon_rmap() userfaultfd: UFFDIO_MOVE uABI Suren Baghdasaryan (3): selftests/mm: call uffd_test_ctx_clear at the end of the test selftests/mm: add uffd_test_case_ops to allow test case-specific operations selftests/mm: add UFFDIO_MOVE ioctl test Documentation/admin-guide/mm/userfaultfd.rst | 3 + fs/userfaultfd.c | 72 +++ include/linux/rmap.h | 5 + include/linux/userfaultfd_k.h | 11 + include/uapi/linux/userfaultfd.h | 29 +- mm/huge_memory.c | 122 ++++ mm/khugepaged.c | 3 + mm/rmap.c | 30 + mm/userfaultfd.c | 614 +++++++++++++++++++ tools/testing/selftests/mm/uffd-common.c | 39 +- tools/testing/selftests/mm/uffd-common.h | 9 + tools/testing/selftests/mm/uffd-stress.c | 5 +- tools/testing/selftests/mm/uffd-unit-tests.c | 192 ++++++ 13 files changed, 1130 insertions(+), 4 deletions(-) -- 2.43.0.rc2.451.g8631bc7472-goog

6 days, 8 hours

7
43
0 0

[PATCH 0/4] mm: permit guard regions for file-backed/shmem mappings

by Lorenzo Stoakes

The guard regions feature was initially implemented to support anonymous mappings only, excluding shmem. This was done such as to introduce the feature carefully and incrementally and to be conservative when considering the various caveats and corner cases that are applicable to file-backed mappings but not to anonymous ones. Now this feature has landed in 6.13, it is time to revisit this and to extend this functionality to file-backed and shmem mappings. In order to make this maximally useful, and since one may map file-backed mappings read-only (for instance ELF images), we also remove the restriction on read-only mappings and permit the establishment of guard regions in any non-hugetlb, non-mlock()'d mapping. It is permissible to permit the establishment of guard regions in read-only mappings because the guard regions only reduce access to the mapping, and when removed simply reinstate the existing attributes of the underlying VMA, meaning no access violations can occur. While the change in kernel code introduced in this series is small, the majority of the effort here is spent in extending the testing to assert that the feature works correctly across numerous file-backed mapping scenarios. Every single guard region self-test performed against anonymous memory (which is relevant and not anon-only) has now been updated to also be performed against shmem and a mapping of a file in the working directory. This confirms that all cases also function correctly for file-backed guard regions. In addition a number of other tests are added for specific file-backed mapping scenarios. There are a number of other concerns that one might have with regard to guard regions, addressed below: Readahead ~~~~~~~~~ Readahead is a process through which the page cache is populated on the assumption that sequential reads will occur, thus amortising I/O and, through a clever use of the PG_readahead folio flag establishing during major fault and checked upon minor fault, provides for asynchronous I/O to occur as dat is processed, reducing I/O stalls as data is faulted in. Guard regions do not alter this mechanism which operations at the folio and fault level, but do of course prevent the faulting of folios that would otherwise be mapped. In the instance of a major fault prior to a guard region, synchronous readahead will occur including populating folios in the page cache which the guard regions will, in the case of the mapping in question, prevent access to. In addition, if PG_readahead is placed in a folio that is now inaccessible, this will prevent asynchronous readahead from occurring as it would otherwise do. However, there are mechanisms for heuristically resetting this within readahead regardless, which will 'recover' correct readahead behaviour. Readahead presumes sequential data access, the presence of a guard region clearly indicates that, at least in the guard region, no such sequential access will occur, as it cannot occur there. So this should have very little impact on any real workload. The far more important point is as to whether readahead causes incorrect or inappropriate mapping of ranges disallowed by the presence of guard regions - this is not the case, as readahead does not 'pre-fault' memory in this fashion. At any rate, any mechanism which would attempt to do so would hit the usual page fault paths, which correctly handle PTE markers as with anonymous mappings. Fault-Around ~~~~~~~~~~~~ The fault-around logic, in a similar vein to readahead, attempts to improve efficiency with regard to file-backed memory mappings, however it differs in that it does not try to fetch folios into the page cache that are about to be accessed, but rather pre-maps a range of folios around the faulting address. Guard regions making use of PTE markers makes this relatively trivial, as this case is already handled - see filemap_map_folio_range() and filemap_map_order0_folio() - in both instances, the solution is to simply keep the established page table mappings and let the fault handler take care of PTE markers, as per the comment: /* * NOTE: If there're PTE markers, we'll leave them to be * handled in the specific fault path, and it'll prohibit * the fault-around logic. */ This works, as establishing guard regions results in page table mappings with PTE markers, and clearing them removes them. Truncation ~~~~~~~~~~ File truncation will not eliminate existing guard regions, as the truncation operation will ultimately zap the range via unmap_mapping_range(), which specifically excludes PTE markers. Zapping ~~~~~~~ Zapping is, as with anonymous mappings, handled by zap_nonpresent_ptes(), which specifically deals with guard entries, leaving them intact except in instances such as process teardown or munmap() where they need to be removed. Reclaim ~~~~~~~ When reclaim is performed on file-backed folios, it ultimately invokes try_to_unmap_one() via the rmap. If the folio is non-large, then map_pte() will ultimately abort the operation for the guard region mapping. If large, then check_pte() will determine that this is a non-device private entry/device-exclusive entry 'swap' PTE and thus abort the operation in that instance. Therefore, no odd things happen in the instance of reclaim being attempted upon a file-backed guard region. Hole Punching ~~~~~~~~~~~~~ This updates the page cache and ultimately invokes unmap_mapping_range(), which explicitly leaves PTE markers in place. Because the establishment of guard regions zapped any existing mappings to file-backed folios, once the guard regions are removed then the hole-punched region will be faulted in as usual and everything will behave as expected. Lorenzo Stoakes (4): mm: allow guard regions in file-backed and read-only mappings selftests/mm: rename guard-pages to guard-regions tools/selftests: expand all guard region tests to file-backed tools/selftests: add file/shmem-backed mapping guard region tests mm/madvise.c | 8 +- tools/testing/selftests/mm/.gitignore | 2 +- tools/testing/selftests/mm/Makefile | 2 +- .../mm/{guard-pages.c => guard-regions.c} | 921 ++++++++++++++++-- 4 files changed, 821 insertions(+), 112 deletions(-) rename tools/testing/selftests/mm/{guard-pages.c => guard-regions.c} (58%) -- 2.48.1

6 days, 22 hours

7
63
0 0

[PATCH v2 1/2] time/timekeeping: Fix possible inconsistencies in _COARSE clockids

by John Stultz

Lei Chen raised an issue with CLOCK_MONOTONIC_COARSE seeing time inconsistencies. Lei tracked down that this was being caused by the adjustment tk->tkr_mono.xtime_nsec -= offset; which is made to compensate for the unaccumulated cycles in offset when the mult value is adjusted forward, so that the non-_COARSE clockids don't see inconsistencies. However, the _COARSE clockids don't use the mult*offset value in their calculations, so this subtraction can cause the _COARSE clock ids to jump back a bit. Now, by design, this negative adjustment should be fine, because the logic run from timekeeping_adjust() is done after we accumulate approx mult*interval_cycles into xtime_nsec. The accumulated (mult*interval_cycles) will be larger then the (mult_adj*offset) value subtracted from xtime_nsec, and both operations are done together under the tk_core.lock, so the net change to xtime_nsec should always be positive. However, do_adjtimex() calls into timekeeping_advance() as well, since we want to apply the ntp freq adjustment immediately. In this case, we don't return early when the offset is smaller then interval_cycles, so we don't end up accumulating any time into xtime_nsec. But we do go on to call timekeeping_adjust(), which modifies the mult value, and subtracts from xtime_nsec to correct for the new mult value. Here because we did not accumulate anything, we have a window where the _COARSE clockids that don't utilize the mult*offset value, can see an inconsistency. So to fix this, rework the timekeeping_advance() logic a bit so that when we are called from do_adjtimex(), we call timekeeping_forward(), to first accumulate the sub-interval time into xtime_nsec. Then with no unaccumulated cycles in offset, we can do the mult adjustment without worry of the subtraction having an impact. Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Stephen Boyd <sboyd(a)kernel.org> Cc: Anna-Maria Behnsen <anna-maria(a)linutronix.de> Cc: Frederic Weisbecker <frederic(a)kernel.org> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Miroslav Lichvar <mlichvar(a)redhat.com> Cc: linux-kselftest(a)vger.kernel.org Cc: kernel-team(a)android.com Cc: Lei Chen <lei.chen(a)smartx.com> Fixes: da15cfdae033 ("time: Introduce CLOCK_REALTIME_COARSE") Reported-by: Lei Chen <lei.chen(a)smartx.com> Closes: https://lore.kernel.org/lkml/20250310030004.3705801-1-lei.chen@smartx.com/ Diagnosed-by: Thomas Gleixner <tglx(a)linutronix.de> Additional-fixes-by: Thomas Gleixner <tglx(a)linutronix.de> Signed-off-by: John Stultz <jstultz(a)google.com> --- v2: Include fixes from Thomas, dropping the unnecessary clock_set setting, and instead clearing ntp_error, along with some other minor tweaks. --- kernel/time/timekeeping.c | 94 ++++++++++++++++++++++++++++----------- 1 file changed, 69 insertions(+), 25 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 1e67d076f1955..929846b8b45ab 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -682,20 +682,19 @@ static void timekeeping_update_from_shadow(struct tk_data *tkd, unsigned int act } /** - * timekeeping_forward_now - update clock to the current time + * timekeeping_forward - update clock to given cycle now value * @tk: Pointer to the timekeeper to update + * @cycle_now: Current clocksource read value * * Forward the current clock to update its state since the last call to * update_wall_time(). This is useful before significant clock changes, * as it avoids having to deal with this time offset explicitly. */ -static void timekeeping_forward_now(struct timekeeper *tk) +static void timekeeping_forward(struct timekeeper *tk, u64 cycle_now) { - u64 cycle_now, delta; + u64 delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask, + tk->tkr_mono.clock->max_raw_delta); - cycle_now = tk_clock_read(&tk->tkr_mono); - delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask, - tk->tkr_mono.clock->max_raw_delta); tk->tkr_mono.cycle_last = cycle_now; tk->tkr_raw.cycle_last = cycle_now; @@ -710,6 +709,21 @@ static void timekeeping_forward_now(struct timekeeper *tk) } } +/** + * timekeeping_forward_now - update clock to the current time + * @tk: Pointer to the timekeeper to update + * + * Forward the current clock to update its state since the last call to + * update_wall_time(). This is useful before significant clock changes, + * as it avoids having to deal with this time offset explicitly. + */ +static void timekeeping_forward_now(struct timekeeper *tk) +{ + u64 cycle_now = tk_clock_read(&tk->tkr_mono); + + timekeeping_forward(tk, cycle_now); +} + /** * ktime_get_real_ts64 - Returns the time of day in a timespec64. * @ts: pointer to the timespec to be set @@ -2151,6 +2165,54 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset, return offset; } +static u64 timekeeping_accumulate(struct timekeeper *tk, u64 offset, + enum timekeeping_adv_mode mode, + unsigned int *clock_set) +{ + int shift = 0, maxshift; + + /* + * TK_ADV_FREQ indicates that adjtimex(2) directly set the + * frequency or the tick length. + * + * Accumulate the offset, so that the new multiplier starts from + * now. This is required as otherwise for offsets, which are + * smaller than tk::cycle_interval, timekeeping_adjust() could set + * xtime_nsec backwards, which subsequently causes time going + * backwards in the coarse time getters. But even for the case + * where offset is greater than tk::cycle_interval the periodic + * accumulation does not have much value. + * + * Also reset tk::ntp_error as it does not make sense to keep the + * old accumulated error around in this case. + */ + if (mode == TK_ADV_FREQ) { + timekeeping_forward(tk, tk->tkr_mono.cycle_last + offset); + tk->ntp_error = 0; + return 0; + } + + /* + * With NO_HZ we may have to accumulate many cycle_intervals + * (think "ticks") worth of time at once. To do this efficiently, + * we calculate the largest doubling multiple of cycle_intervals + * that is smaller than the offset. We then accumulate that + * chunk in one go, and then try to consume the next smaller + * doubled multiple. + */ + shift = ilog2(offset) - ilog2(tk->cycle_interval); + shift = max(0, shift); + /* Bound shift to one less than what overflows tick_length */ + maxshift = (64 - (ilog2(ntp_tick_length()) + 1)) - 1; + shift = min(shift, maxshift); + while (offset >= tk->cycle_interval) { + offset = logarithmic_accumulation(tk, offset, shift, clock_set); + if (offset < tk->cycle_interval << shift) + shift--; + } + return offset; +} + /* * timekeeping_advance - Updates the timekeeper to the current time and * current NTP tick length @@ -2160,7 +2222,6 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode) struct timekeeper *tk = &tk_core.shadow_timekeeper; struct timekeeper *real_tk = &tk_core.timekeeper; unsigned int clock_set = 0; - int shift = 0, maxshift; u64 offset; guard(raw_spinlock_irqsave)(&tk_core.lock); @@ -2177,24 +2238,7 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode) if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK) return false; - /* - * With NO_HZ we may have to accumulate many cycle_intervals - * (think "ticks") worth of time at once. To do this efficiently, - * we calculate the largest doubling multiple of cycle_intervals - * that is smaller than the offset. We then accumulate that - * chunk in one go, and then try to consume the next smaller - * doubled multiple. - */ - shift = ilog2(offset) - ilog2(tk->cycle_interval); - shift = max(0, shift); - /* Bound shift to one less than what overflows tick_length */ - maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1; - shift = min(shift, maxshift); - while (offset >= tk->cycle_interval) { - offset = logarithmic_accumulation(tk, offset, shift, &clock_set); - if (offset < tk->cycle_interval<<shift) - shift--; - } + offset = timekeeping_accumulate(tk, offset, mode, &clock_set); /* Adjust the multiplier to correct NTP error */ timekeeping_adjust(tk, offset); -- 2.49.0.395.g12beb8f557-goog

1 week, 3 days

3
22
0 0

2025

2024

2023

2022

2021

2020

2019

2018

2017

Linux-kselftest-mirror March 2025