[PATCH v3 0/9] KVM: x86/pmu: Guest Architectural LBR Enabling

Like Xu
2021-03-03T18:11:46Z

Hi geniuses,

Please help review the new version of Arch LBR enabling patch set.

The Architectural Last Branch Records (LBRs) is publiced
in the 319433-040 release of Intel Architecture Instruction
Set Extensions and Future Features Programming Reference[0].

The main advantages for the Arch LBR users are [1]:
- Faster context switching due to XSAVES support and faster reset of
LBR MSRs via the new DEPTH MSR
- Faster LBR read for a non-PEBS event due to XSAVES support, which
lowers the overhead of the NMI handler.
- Linux kernel can support the LBR features without knowing the model
number of the current CPU.

It's based on the kvm/queue tree plus two commits from kvm/intel tree:
- 'fea4ab260645 ("KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS")'
- '0ccd14126cb2 ("KVM: x86: Report XSS as an MSR to be saved if there are supported features")'

Please check more details in each commit and feel free to comment.

[0] https://software.intel.com/content/www/us/en/develop/download/
intel-architecture-instruction-set-extensions-and-future-features-programming-reference.html
[1] https://lore.kernel.org/lkml/1593780569-62993-1-git-send-email-kan.liang@linux.intel.com/

---
v2->v3 Changelog:
- Add host patches (0001-0004) to support guest Arch LBR;
- Fix arch_lbr_depth_is_valid() check condition; [Sean]
- Fix usage of KVM_ARCH_LBR_CTL_MASK;
- Fix intel_pmu_legacy_freezing_lbrs_on_pmi();
- Reset GUEST_IA32_LBR_CTL in the vmx_vcpu_reset();
- Refine intel_pmu_lbr_is_compatible();
- Simplify lbr_enable check and its usage;
- Add Arch LBR msrs to is_valid_passthrough_msr();
- Make XSAVE support for Arch LBR as a separate patch;

Previous:
https://lore.kernel.org/kvm/20210203135714.318356-1-like.xu@linux.intel.com/

Like Xu (9):
perf/x86/intel: Fix a comment about guest LBR support
perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers
perf/x86/lbr: Skip checking for the existence of LBR_TOS for Arch LBR
perf/x86/lbr: Use GFP_ATOMIC for cpuc->lbr_xsave memory allocation
KVM: vmx/pmu: Add MSR_ARCH_LBR_DEPTH emulation for Arch LBR
KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL emulation for Arch LBR
KVM: vmx/pmu: Add Arch LBR emulation and its VMCS field
KVM: x86: Expose Architectural LBR CPUID leaf
KVM: x86: Add XSAVE Support for Architectural LBRs

arch/x86/events/intel/core.c | 5 +-
arch/x86/events/intel/lbr.c | 6 +-
arch/x86/include/asm/vmx.h | 4 ++
arch/x86/kvm/cpuid.c | 25 ++++++++-
arch/x86/kvm/vmx/capabilities.h | 25 ++++++---
arch/x86/kvm/vmx/pmu_intel.c | 99 +++++++++++++++++++++++++++++----
arch/x86/kvm/vmx/vmx.c | 22 +++++++-
arch/x86/kvm/vmx/vmx.h | 3 +
arch/x86/kvm/x86.c | 2 +
9 files changed, 164 insertions(+), 27 deletions(-)

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2.29.2