On Tue, Jul 13, 2021 at 3:10 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> Enum values have to be exported to userspace since the formatting is not
> done in the kernel. Without doing this perf maps RET_PF_FIXED and
> RET_PF_SPURIOUS to 0, which results in incorrect output:
>
> $ perf record -a -e kvmmmu:fast_page_fault --filter "ret==3" -- ./access_tracking_perf_test
> $ perf script | head -1
> [...] new 610006048d25877 spurious 0 fixed 0 <------ should be 1
>
> Fix this by exporting the enum values to userspace with TRACE_DEFINE_ENUM.
>
> Fixes: c4371c2a682e ("KVM: x86/mmu: Return unique RET_PF_* values if the fault was fixed")
Reviewed-by: Ben Gardon <bgardon@xxxxxxxxxx>
> Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu_internal.h | 3 +++
> arch/x86/kvm/mmu/mmutrace.h | 6 ++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index 35567293c1fd..626cb848dab4 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -140,6 +140,9 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
> * RET_PF_INVALID: the spte is invalid, let the real page fault path update it.
> * RET_PF_FIXED: The faulting entry has been fixed.
> * RET_PF_SPURIOUS: The faulting entry was already fixed, e.g. by another vCPU.
> + *
> + * Any names added to this enum should be exported to userspace for use in
> + * tracepoints via TRACE_DEFINE_ENUM() in mmutrace.h
> */
> enum {
> RET_PF_RETRY = 0,
> diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h
> index efbad33a0645..2924a4081a19 100644
> --- a/arch/x86/kvm/mmu/mmutrace.h
> +++ b/arch/x86/kvm/mmu/mmutrace.h
> @@ -54,6 +54,12 @@
> { PFERR_RSVD_MASK, "RSVD" }, \
> { PFERR_FETCH_MASK, "F" }
>
> +TRACE_DEFINE_ENUM(RET_PF_RETRY);
> +TRACE_DEFINE_ENUM(RET_PF_EMULATE);
> +TRACE_DEFINE_ENUM(RET_PF_INVALID);
> +TRACE_DEFINE_ENUM(RET_PF_FIXED);
> +TRACE_DEFINE_ENUM(RET_PF_SPURIOUS);
> +
> /*
> * A pagetable walk has started
> */
> --
> 2.32.0.93.g670b81a890-goog
>
