[PATCH v4 00/11] KVM: x86/pmu: Guest Architectural LBR Enabling

Like Xu
2021-03-14T16:01:08Z

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/

---
v3->v4 Changelog:
- Add one more host patch to reuse ARCH_LBR_CTL_MASK;
- Add reserve_lbr_buffers() instead of using GFP_ATOMIC;
- Fia a bug in the arch_lbr_depth_is_valid();
- Add LBR_CTL_EN to unify DEBUGCTLMSR_LBR and ARCH_LBR_CTL_LBREN;
- Add vmx->host_lbrctlmsr to save/restore host values;
- Add KVM_SUPPORTED_XSS to refactoring supported_xss;
- Clear Arch_LBR ans its XSS bit if it's not supported;
- Add negative testing to the related kvm-unit-tests;
- Refine code and commit messages;

Previous:
https://lore.kernel.org/kvm/20210303135756.1546253-1-like.xu@linux.intel.com/

Like Xu (11):
perf/x86/intel: Fix the comment about guest LBR support on KVM
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: Move cpuc->lbr_xsave allocation out of sleeping region
perf/x86: Move ARCH_LBR_CTL_MASK definition to include/asm/msr-index.h
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: Refine the matching and clearing logic for supported_xss
KVM: x86: Add XSAVE Support for Architectural LBRs

arch/x86/events/core.c | 8 ++-
arch/x86/events/intel/bts.c | 2 +-
arch/x86/events/intel/core.c | 6 +-
arch/x86/events/intel/lbr.c | 28 +++++----
arch/x86/events/perf_event.h | 8 ++-
arch/x86/include/asm/msr-index.h | 1 +
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 | 103 ++++++++++++++++++++++++++++---
arch/x86/kvm/vmx/vmx.c | 50 +++++++++++++--
arch/x86/kvm/vmx/vmx.h | 4 ++
arch/x86/kvm/x86.c | 6 +-
13 files changed, 227 insertions(+), 43 deletions(-)

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2.29.2