This patch set enables the Intel flexible return and event delivery (FRED) architecture with KVM VMX to allow guests to utilize FRED.
The FRED architecture defines simple new transitions that change privilege level (ring transitions). The FRED architecture was designed with the following goals:
1) Improve overall performance and response time by replacing event delivery through the interrupt descriptor table (IDT event delivery) and event return by the IRET instruction with lower latency transitions.
2) Improve software robustness by ensuring that event delivery establishes the full supervisor context and that event return establishes the full user context.
The new transitions defined by the FRED architecture are FRED event delivery and, for returning from events, two FRED return instructions. FRED event delivery can effect a transition from ring 3 to ring 0, but it is used also to deliver events incident to ring 0. One FRED instruction (ERETU) effects a return from ring 0 to ring 3, while the other (ERETS) returns while remaining in ring 0. Collectively, FRED event delivery and the FRED return instructions are FRED transitions.
Intel VMX architecture is extended to run FRED guests, and the changes are majorly:
1) New VMCS fields for FRED context management, which includes two new event data VMCS fields, eight new guest FRED context VMCS fields and eight new host FRED context VMCS fields.
2) VMX nested-Exception support for proper virtualization of stack levels introduced with FRED architecture.
Search for the latest FRED spec in most search engines with this search pattern:
site:intel.com FRED (flexible return and event delivery) specification
We want to send out the FRED VMX patch set for review while the FRED native patch set v12 is being reviewed @ https://lkml.kernel.org/kvm/20231003062458.23552-1-xin3.li@intel.com/. For easier review, I have set up a base tree with the latest FRED native patch set on top of tip tree in the 'fred_v12' branch of repo https://github.com/xinli-intel/linux-fred-public.git.
Patch 1-2 are cleanups to VMX basic and misc MSRs, which were sent out earlier as a preparation for FRED changes: https://lore.kernel.org/kvm/20231030233940.438233-1-xin@zytor.com/.
Patch 3-14 add FRED support to VMX. Patch 15-18 add FRED support to nested VMX. Patch 19 exposes FRED to KVM guests to complete the enabling. Patch 20-23 adds FRED selftests.
Shan Kang (1): KVM: selftests: Add fred exception tests
Xin Li (22): KVM: VMX: Cleanup VMX basic information defines and usages KVM: VMX: Cleanup VMX misc information defines and usages KVM: VMX: Add support for the secondary VM exit controls KVM: x86: Mark CR4.FRED as not reserved KVM: VMX: Initialize FRED VM entry/exit controls in vmcs_config KVM: VMX: Defer enabling FRED MSRs save/load until after set CPUID KVM: VMX: Disable intercepting FRED MSRs KVM: VMX: Initialize VMCS FRED fields KVM: VMX: Switch FRED RSP0 between host and guest KVM: VMX: Add support for FRED context save/restore KVM: x86: Add kvm_is_fred_enabled() KVM: VMX: Handle FRED event data KVM: VMX: Handle VMX nested exception for FRED KVM: VMX: Dump FRED context in dump_vmcs() KVM: nVMX: Add support for the secondary VM exit controls KVM: nVMX: Add FRED VMCS fields KVM: nVMX: Add support for VMX FRED controls KVM: nVMX: Add VMCS FRED states checking KVM: x86: Allow FRED/LKGS/WRMSRNS to be exposed to guests KVM: selftests: Add FRED VMCS fields to evmcs KVM: selftests: Run debug_regs test with FRED enabled KVM: selftests: Add a new VM guest mode to run user level code
Documentation/virt/kvm/x86/nested-vmx.rst | 19 + arch/x86/include/asm/hyperv-tlfs.h | 19 + arch/x86/include/asm/kvm_host.h | 9 +- arch/x86/include/asm/msr-index.h | 15 +- arch/x86/include/asm/vmx.h | 57 ++- arch/x86/kvm/cpuid.c | 4 +- arch/x86/kvm/kvm_cache_regs.h | 10 + arch/x86/kvm/svm/svm.c | 4 +- arch/x86/kvm/vmx/capabilities.h | 20 +- arch/x86/kvm/vmx/hyperv.c | 61 ++- arch/x86/kvm/vmx/nested.c | 315 ++++++++++++-- arch/x86/kvm/vmx/nested.h | 2 +- arch/x86/kvm/vmx/vmcs.h | 1 + arch/x86/kvm/vmx/vmcs12.c | 19 + arch/x86/kvm/vmx/vmcs12.h | 38 ++ arch/x86/kvm/vmx/vmcs_shadow_fields.h | 6 +- arch/x86/kvm/vmx/vmx.c | 404 ++++++++++++++++-- arch/x86/kvm/vmx/vmx.h | 14 +- arch/x86/kvm/x86.c | 55 ++- arch/x86/kvm/x86.h | 5 +- tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/include/kvm_util_base.h | 1 + .../selftests/kvm/include/x86_64/evmcs.h | 146 +++++++ .../selftests/kvm/include/x86_64/processor.h | 33 ++ .../selftests/kvm/include/x86_64/vmx.h | 20 + tools/testing/selftests/kvm/lib/kvm_util.c | 5 +- .../selftests/kvm/lib/x86_64/processor.c | 15 +- tools/testing/selftests/kvm/lib/x86_64/vmx.c | 4 +- .../testing/selftests/kvm/x86_64/debug_regs.c | 50 ++- .../testing/selftests/kvm/x86_64/fred_test.c | 262 ++++++++++++ 30 files changed, 1464 insertions(+), 150 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86_64/fred_test.c
base-commit: d49b86c24e836941c85c4906e9519fca9426a6e0