This series provides initial support for the ARMv9 Scalable Matrix Extension (SME). SME takes the approach used for vectors in SVE and extends this to provide architectural support for matrix operations. A more detailed overview can be found in [1].
For the kernel SME can be thought of as a series of features which are intended to be used together by applications but operate mostly orthogonally:
- The ZA matrix register. - Streaming mode, in which ZA can be accessed and a subset of SVE features are available. - A second vector length, used for streaming mode SVE and ZA and controlled using a similar interface to that for SVE. - TPIDR2, a new userspace controllable system register intended for use by the C library for storing context related to the ZA ABI.
A substantial part of the series is dedicated to refactoring the existing SVE support so that we don't need to duplicate code for handling vector lengths and the SVE registers, this involves creating an array of vector types and making the users take the vector type as a parameter. I'm not 100% happy with this but wasn't able to come up with anything better, duplicating code definitely felt like a bad idea so this felt like the least bad thing. If this approach makes sense to people it might make sense to split this off into a separate series and/or merge it while the rest is pending review to try to make things a little more digestable, the series is very large so it'd probably make things easier to digest if some of the preparatory refactoring could be merged before the rest is ready.
One feature of the architecture of particular note is that switching to and from streaming mode may change the size of and invalidate the contents of the SVE registers, and when in streaming mode the FFR is not accessible. This complicates aspects of the ABI like signal handling and ptrace.
This initial implementation is mainly intended to get the ABI in place, there are several areas which will be worked on going forwards - some of these will be blockers, others could be handled in followup serieses:
- SME is currently not supported for KVM guests, this will be done as a followup series. A host system can use SME and run KVM guests but SME is not available in the guests. - The KVM host support is done in a very simplistic way, were anyone to attempt to use it in production there would be performance impacts on hosts with SME support. As part of this we also add enumeration of fine grained traps. - There is not currently ptrace or signal support TPIDR2, this will be done as a followup series. - No support is currently provided for scheduler control of SME or SME applications, given the size of the SME register state the context switch overhead may be noticable so this may be needed especially for real time applications. Similar concerns already exist for larger SVE vector lengths but are amplified for SME, particularly as the vector length increases. - There has been no work on optimising the performance of anything the kernel does.
It is not expected that any systems will be encountered that support SME but not SVE, SME is an ARMv9 feature and SVE is mandatory for ARMv9. The code attempts to handle any such systems that are encountered but this hasn't been tested extensively.
v8: - Rebase onto v5.17-rc1. - Support interoperation with KVM, SME is disabled for KVM guests with minimal handling for cleaning up SME state when entering and leaving the guest. - Document and implement that signal handlers are invoked with ZA and streaming mode disabled. - Use the RDSVL instruction introduced in EAC2 of the architecture to obtain the streaming mode vector length during enumeration, ZA state loading/saving and in test programs. - Store a pointer to SVCR in fpsimd_last_state and use it in fpsimd_save() for interoperation with KVM. - Add a test case sme_trap_no_sm checking that we generate a SIGILL when using an instruction that requires streaming mode without enabling it. - Add basic ZA context form validation to testcases helper library. - Move signal tests over to validating streaming VL from ZA information. - Pulled in patch removing ARRAY_SIZE() so that kselftest builds cleanly and to avoid trivial conflicts. v7: - Rebase onto v5.16-rc3. - Reduce indentation when supporting custom triggers for signal tests as suggested by Catalin. - Change to specifying a width for all CPU features rather than adding single bit specific infrastructure. - Don't require zeroing of non-shared SVE state during syscalls. v6: - Rebase onto v5.16-rc1. - Return to disabling TIF_SVE on kernel entry even if we have SME state, this avoids the need for KVM to handle the case where TIF_SVE is set on guest entry. - Add syscall-abi.h to SME updates to syscall-abi, mistakenly omitted from commit. v5: - Rebase onto currently merged SVE and kselftest patches. - Add support for the FA64 option, introduced in the recently published EAC1 update to the specification. - Pull in test program for the syscall ABI previously sent separately with some revisions and add coverage for the SME ABI. - Fix checking for options with 1 bit fields in ID_AA64SMFR0_EL1. - Minor fixes and clarifications to the ABI documentation. v4: - Rebase onto merged patches. - Remove an uneeded NULL check in vec_proc_do_default_vl(). - Include patch to factor out utility routines in kselftests written in assembler. - Specify -ffreestanding when building TPIDR2 test. v3: - Skip FFR rather than predicate registers in sve_flush_live(). - Don't assume a bool is all zeros in sve_flush_live() as per AAPCS. - Don't redundantly specify a zero index when clearing FFR. v2: - Fix several issues with !SME and !SVE configurations. - Preserve TPIDR2 when creating a new thread/process unless CLONE_SETTLS is set. - Report traps due to using features in an invalid mode as SIGILL. - Spell out streaming mode behaviour in SVE ABI documentation more directly. - Document TPIDR2 in the ABI document. - Use SMSTART and SMSTOP rather than read/modify/write sequences. - Rework logic for exiting streaming mode on syscall. - Don't needlessly initialise SVCR on access trap. - Always restore SME VL for userspace if SME traps are disabled. - Only yield to encourage preemption every 128 iterations in za-test, otherwise do a getpid(), and validate SVCR after syscall. - Leave streaming mode disabled except when reading the vector length in za-test, and disable ZA after detecting a mismatch. - Add SME support to vlset. - Clarifications and typo fixes in comments. - Move sme_alloc() forward declaration back a patch.
[1] https://community.arm.com/developer/ip-products/processors/b/processors-ip-b...
Mark Brown (38): arm64: cpufeature: Always specify and use a field width for capabilities arm64: Add feature detection for fine grained traps kselftest/arm64: Remove local ARRAY_SIZE() definitions arm64/sme: Provide ABI documentation for SME arm64/sme: System register and exception syndrome definitions arm64/sme: Manually encode SME instructions arm64/sme: Early CPU setup for SME arm64/sme: Basic enumeration support arm64/sme: Identify supported SME vector lengths at boot arm64/sme: Implement sysctl to set the default vector length arm64/sme: Implement vector length configuration prctl()s arm64/sme: Implement support for TPIDR2 arm64/sme: Implement SVCR context switching arm64/sme: Implement streaming SVE context switching arm64/sme: Implement ZA context switching arm64/sme: Implement traps and syscall handling for SME arm64/sme: Disable ZA and streaming mode when handling signals arm64/sme: Implement streaming SVE signal handling arm64/sme: Implement ZA signal handling arm64/sme: Implement ptrace support for streaming mode SVE registers arm64/sme: Add ptrace support for ZA arm64/sme: Disable streaming mode and ZA when flushing CPU state arm64/sme: Save and restore streaming mode over EFI runtime calls KVM: arm64: Hide SME system registers from guests KVM: arm64: Trap SME usage in guest KVM: arm64: Handle SME host state when running guests arm64/sme: Provide Kconfig for SME kselftest/arm64: sme: Add streaming SME support to vlset kselftest/arm64: Add tests for TPIDR2 kselftest/arm64: Extend vector configuration API tests to cover SME kselftest/arm64: sme: Provide streaming mode SVE stress test kselftest/arm64: signal: Allow tests to be incompatible with features kselftest/arm64: signal: Handle ZA signal context in core code kselftest/arm64: Add stress test for SME ZA context switching kselftest/arm64: signal: Add SME signal handling tests kselftest/arm64: Add streaming SVE to SVE ptrace tests kselftest/arm64: Add coverage for the ZA ptrace interface kselftest/arm64: Add SME support to syscall ABI test
Documentation/arm64/elf_hwcaps.rst | 33 + Documentation/arm64/index.rst | 1 + Documentation/arm64/sme.rst | 432 +++++++++++++ Documentation/arm64/sve.rst | 70 ++- arch/arm64/Kconfig | 11 + arch/arm64/include/asm/cpu.h | 4 + arch/arm64/include/asm/cpufeature.h | 25 + arch/arm64/include/asm/el2_setup.h | 64 +- arch/arm64/include/asm/esr.h | 13 +- arch/arm64/include/asm/exception.h | 1 + arch/arm64/include/asm/fpsimd.h | 110 +++- arch/arm64/include/asm/fpsimdmacros.h | 86 +++ arch/arm64/include/asm/hwcap.h | 8 + arch/arm64/include/asm/kvm_arm.h | 1 + arch/arm64/include/asm/kvm_host.h | 4 + arch/arm64/include/asm/processor.h | 18 +- arch/arm64/include/asm/sysreg.h | 64 ++ arch/arm64/include/asm/thread_info.h | 2 + arch/arm64/include/uapi/asm/hwcap.h | 8 + arch/arm64/include/uapi/asm/ptrace.h | 69 ++- arch/arm64/include/uapi/asm/sigcontext.h | 55 +- arch/arm64/kernel/cpufeature.c | 284 +++++++-- arch/arm64/kernel/cpuinfo.c | 13 + arch/arm64/kernel/entry-common.c | 11 + arch/arm64/kernel/entry-fpsimd.S | 36 ++ arch/arm64/kernel/fpsimd.c | 585 ++++++++++++++++-- arch/arm64/kernel/process.c | 28 +- arch/arm64/kernel/ptrace.c | 356 +++++++++-- arch/arm64/kernel/signal.c | 194 +++++- arch/arm64/kernel/syscall.c | 34 +- arch/arm64/kernel/traps.c | 1 + arch/arm64/kvm/fpsimd.c | 45 +- arch/arm64/kvm/hyp/nvhe/switch.c | 30 + arch/arm64/kvm/hyp/vhe/switch.c | 10 +- arch/arm64/kvm/sys_regs.c | 9 +- arch/arm64/tools/cpucaps | 3 + include/uapi/linux/elf.h | 2 + include/uapi/linux/prctl.h | 9 + kernel/sys.c | 12 + tools/testing/selftests/arm64/abi/.gitignore | 1 + tools/testing/selftests/arm64/abi/Makefile | 9 +- .../selftests/arm64/abi/syscall-abi-asm.S | 69 ++- .../testing/selftests/arm64/abi/syscall-abi.c | 205 +++++- .../testing/selftests/arm64/abi/syscall-abi.h | 15 + tools/testing/selftests/arm64/abi/tpidr2.c | 298 +++++++++ tools/testing/selftests/arm64/fp/.gitignore | 4 + tools/testing/selftests/arm64/fp/Makefile | 12 +- tools/testing/selftests/arm64/fp/rdvl-sme.c | 14 + tools/testing/selftests/arm64/fp/rdvl.S | 8 + tools/testing/selftests/arm64/fp/rdvl.h | 1 + tools/testing/selftests/arm64/fp/ssve-stress | 59 ++ tools/testing/selftests/arm64/fp/sve-ptrace.c | 13 +- tools/testing/selftests/arm64/fp/sve-test.S | 30 + tools/testing/selftests/arm64/fp/vec-syscfg.c | 10 + tools/testing/selftests/arm64/fp/vlset.c | 10 +- tools/testing/selftests/arm64/fp/za-ptrace.c | 354 +++++++++++ tools/testing/selftests/arm64/fp/za-stress | 59 ++ tools/testing/selftests/arm64/fp/za-test.S | 426 +++++++++++++ .../testing/selftests/arm64/signal/.gitignore | 2 + .../selftests/arm64/signal/test_signals.h | 5 + .../arm64/signal/test_signals_utils.c | 40 +- .../arm64/signal/test_signals_utils.h | 2 + .../testcases/fake_sigreturn_sme_change_vl.c | 92 +++ .../arm64/signal/testcases/sme_trap_no_sm.c | 38 ++ .../signal/testcases/sme_trap_non_streaming.c | 45 ++ .../arm64/signal/testcases/sme_trap_za.c | 36 ++ .../selftests/arm64/signal/testcases/sme_vl.c | 68 ++ .../arm64/signal/testcases/ssve_regs.c | 129 ++++ .../arm64/signal/testcases/testcases.c | 36 ++ .../arm64/signal/testcases/testcases.h | 3 +- 70 files changed, 4590 insertions(+), 244 deletions(-) create mode 100644 Documentation/arm64/sme.rst create mode 100644 tools/testing/selftests/arm64/abi/syscall-abi.h create mode 100644 tools/testing/selftests/arm64/abi/tpidr2.c create mode 100644 tools/testing/selftests/arm64/fp/rdvl-sme.c create mode 100644 tools/testing/selftests/arm64/fp/ssve-stress create mode 100644 tools/testing/selftests/arm64/fp/za-ptrace.c create mode 100644 tools/testing/selftests/arm64/fp/za-stress create mode 100644 tools/testing/selftests/arm64/fp/za-test.S create mode 100644 tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_sme_change_vl.c create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_trap_no_sm.c create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_trap_non_streaming.c create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_trap_za.c create mode 100644 tools/testing/selftests/arm64/signal/testcases/sme_vl.c create mode 100644 tools/testing/selftests/arm64/signal/testcases/ssve_regs.c
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