[PATCH v2 00/15] Introduce Architectural LBR for vPMU

Yang Weijiang
2022-11-25T06:10:12Z

Intel CPU model-specific LBR(Legacy LBR) has evolved to Architectural
LBR(Arch LBR [0]), it's the replacement of legacy LBR on new platforms.
The native support patches were merged into 5.9 kernel tree, and this
patch series is to enable Arch LBR in vPMU so that guest can benefit
from the feature.

The main advantages of Arch LBR 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.

From end user's point of view, the usage of Arch LBR is the same as
the Legacy LBR that has been merged in the mainline.

Note, in this series, there's one restriction for guest Arch LBR, i.e.,
guest can only set its LBR record depth the same as host's. This is due
to the special behavior of MSR_ARCH_LBR_DEPTH:
1) On write to the MSR, it'll reset all Arch LBR recording MSRs to 0s.
2) XRSTORS resets all record MSRs to 0s if the saved depth mismatches
MSR_ARCH_LBR_DEPTH.
Enforcing the restriction keeps KVM Arch LBR vPMU working flow simple
and straightforward.

Paolo refactored the old series and the resulting patches became the
base of this new series, therefore he's the author of some patches.

[0] https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html
[1] https://lore.kernel.org/lkml/1593780569-62993-1-git-send-email-kan.liang@linux.intel.com/

v1:
https://lore.kernel.org/all/20220831223438.413090-1-weijiang.yang@intel.com/

Changes v2:
1. Removed Paolo's SOBs from some patches. [Sean]
2. Modified some patches due to KVM changes, e.g., SMM/vPMU refactor.
3. Rebased to https://git.kernel.org/pub/scm/virt/kvm/kvm.git : queue branch.

Like Xu (3):
perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers
KVM: vmx/pmu: Emulate MSR_ARCH_LBR_DEPTH for guest Arch LBR
KVM: x86: Add XSAVE Support for Architectural LBR

Paolo Bonzini (4):
KVM: PMU: disable LBR handling if architectural LBR is available
KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL for guest Arch LBR
KVM: VMX: Support passthrough of architectural LBRs
KVM: x86: Refine the matching and clearing logic for supported_xss

Sean Christopherson (1):
KVM: x86: Report XSS as an MSR to be saved if there are supported
features

Yang Weijiang (7):
KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS
KVM: x86: Add Arch LBR MSRs to msrs_to_save_all list
KVM: x86/vmx: Check Arch LBR config when return perf capabilities
KVM: x86/vmx: Disable Arch LBREn bit in #DB and warm reset
KVM: x86/vmx: Save/Restore guest Arch LBR Ctrl msr at SMM entry/exit
KVM: x86: Add Arch LBR data MSR access interface
KVM: x86/cpuid: Advertise Arch LBR feature in CPUID

arch/x86/events/intel/lbr.c | 6 +-
arch/x86/include/asm/kvm_host.h | 3 +
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/include/asm/vmx.h | 4 +
arch/x86/kvm/cpuid.c | 52 +++++++++-
arch/x86/kvm/smm.c | 1 +
arch/x86/kvm/smm.h | 3 +-
arch/x86/kvm/vmx/capabilities.h | 5 +
arch/x86/kvm/vmx/nested.c | 8 ++
arch/x86/kvm/vmx/pmu_intel.c | 161 +++++++++++++++++++++++++++----
arch/x86/kvm/vmx/vmx.c | 74 +++++++++++++-
arch/x86/kvm/vmx/vmx.h | 6 +-
arch/x86/kvm/x86.c | 27 +++++-
13 files changed, 316 insertions(+), 35 deletions(-)

base-commit: da5f28e10aa7df1a925dbc10656cc89d9c061358
--
2.27.0