RE: [PATCH v3 0/5] Guest LBR Enabling

[Gonglei (Arei)]

> -----Original Message-----
> From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On
> Behalf Of Wei Wang
> Sent: Thursday, September 20, 2018 6:06 PM
> To: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; pbonzini@xxxxxxxxxx;
> ak@xxxxxxxxxxxxxxx
> Cc: kan.liang@xxxxxxxxx; peterz@xxxxxxxxxxxxx; mingo@xxxxxxxxxx;
> rkrcmar@xxxxxxxxxx; like.xu@xxxxxxxxx; wei.w.wang@xxxxxxxxx;
> jannh@xxxxxxxxxx; Gonglei (Arei) <arei.gonglei@xxxxxxxxxx>
> Subject: [PATCH v3 0/5] Guest LBR Enabling
> 
> Last Branch Recording (LBR) is a performance monitor unit (PMU) feature
> on Intel CPUs that captures branch related info. This patch series enables
> this feature to KVM guests.
> 
> Here is a conclusion of the fundamental methods that we use:
> 1) the LBR feature is enabled per guest via QEMU setting of
>    KVM_CAP_X86_GUEST_LBR;

Did you send the QEMU parts for guest LBR support?


Thanks,
-Gonglei

> 2) the LBR stack is passed through to the guest for direct accesses after
>    the guest's first access to any of the lbr related MSRs;
> 3) When the guest uses the LBR feature with the user callstack mode, the
>    host will help save/resotre the LBR stack when the vCPU is scheduled
>    out/in.
> 
> ChangeLog:
> v2->v3:
>     - replaces the pv approach with a lazy save approach to saving the lbr
>       stack on vCPU switching;
>     - destroy the host side perf event if the guest is torn down;
>     - remove the unnecessary event->pmu->stop() before calling
>       perf_event_release_kernel().
> v1->v2:
>     - add the per guest LBR capability, KVM_CAP_X86_GUEST_LBR;
>     - save/restore the LBR stack conditionally on the vCPU thread context
>       switching, instead of on VMX transitions;
>     - expose MSR_IA32_PERF_CAPABILITIES to the guest.
> 
> Like Xu (1):
>   KVM/x86/vPMU: Add APIs to support host save/restore the guest lbr
>     stack
> 
> Wei Wang (4):
>   perf/x86: add a function to get the lbr stack
>   KVM/x86: KVM_CAP_X86_GUEST_LBR
>   KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest
>   KVM/x86/lbr: lazy save the guest lbr stack
> 
>  arch/x86/events/intel/lbr.c       |  49 ++++++++++++-
>  arch/x86/events/perf_event.h      |   1 +
>  arch/x86/include/asm/kvm_host.h   |   7 ++
>  arch/x86/include/asm/perf_event.h |  22 ++++++
>  arch/x86/kvm/cpuid.c              |   2 +-
>  arch/x86/kvm/pmu.h                |   8 +++
>  arch/x86/kvm/pmu_intel.c          |  41 +++++++++++
>  arch/x86/kvm/vmx.c                | 144
> ++++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c                |  10 +++
>  include/uapi/linux/kvm.h          |   1 +
>  10 files changed, 281 insertions(+), 4 deletions(-)
> 
> --
> 2.7.4