Re: [PATCH v2 0/7] KVM: x86/pmu: Fix some corner cases including Intel PEBS

[Like Xu <like.xu.linux@gmail.com>]

To catch up on the first -rc, ping beggarly and guiltily.

On 21/7/2022 6:35 pm, Like Xu wrote:
> Good well-designed tests can help us find more bugs, especially when
> the test steps differ from the Linux kernel behaviour in terms of the
> timing of access to virtualized hw resources.
> 
> A new guest PEBS kvm-unit-test constructs a number of typical and
> corner use cases to demonstrate how fragile the earlier PEBS
> enabling patch set is. I prefer to reveal these flaws and fix them
> myself before we receive complaints from projects that rely on it.
> 
> In this patch series, there is one small optimization (006), one hardware
> surprise (002), and most of these fixes have stepped on my little toes.
> 
> Please feel free to run tests, add more or share comments.
> 
> Previous:
> https://lore.kernel.org/kvm/20220713122507.29236-1-likexu@tencent.com/
> 
> V1 -> V2 Changelog:
> - For 3/7, use "hw_idx > -1" and add comment; (Sean)
> - For 4/7, refine commit message and add comment; (Sean)
> - For 6/7, inline reprogram_counter() and restrict pmc->current_config;
> 
> Like Xu (7):
>    perf/x86/core: Update x86_pmu.pebs_capable for ICELAKE_{X,D}
>    perf/x86/core: Completely disable guest PEBS via guest's global_ctrl
>    KVM: x86/pmu: Avoid setting BIT_ULL(-1) to pmu->host_cross_mapped_mask
>    KVM: x86/pmu: Don't generate PEBS records for emulated instructions
>    KVM: x86/pmu: Avoid using PEBS perf_events for normal counters
>    KVM: x86/pmu: Defer reprogram_counter() to kvm_pmu_handle_event()
>    KVM: x86/pmu: Defer counter emulated overflow via pmc->stale_counter
> 
>   arch/x86/events/intel/core.c    |  4 ++-
>   arch/x86/include/asm/kvm_host.h |  6 +++--
>   arch/x86/kvm/pmu.c              | 47 +++++++++++++++++++++------------
>   arch/x86/kvm/pmu.h              |  6 ++++-
>   arch/x86/kvm/svm/pmu.c          |  2 +-
>   arch/x86/kvm/vmx/pmu_intel.c    | 30 ++++++++++-----------
>   6 files changed, 58 insertions(+), 37 deletions(-)
>