On Wed, Jun 09, 2021 at 02:12:38PM -0700, Pawan Gupta wrote:
> Earlier workaround added by commit 400816f60c54 ("perf/x86/intel:
> Implement support for TSX Force Abort") for perf counter interactions
> [1] are not required on some client systems which received a microcode
> update that deprecates TSX.
>
> Bypass the perf workaround when such microcode is enumerated.
>
> [1] Performance Monitoring Impact of Intel® Transactional Synchronization Extension Memory
> http://cdrdv2.intel.com/v1/dl/getContent/604224
>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
> Tested-by: Neelima Krishnan <neelima.krishnan@xxxxxxxxx>
> ---
> arch/x86/events/intel/core.c | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
> index e28892270c58..b5953e1e59a2 100644
> --- a/arch/x86/events/intel/core.c
> +++ b/arch/x86/events/intel/core.c
> @@ -6016,10 +6016,24 @@ __init int intel_pmu_init(void)
> intel_pmu_pebs_data_source_skl(pmem);
>
> if (boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) {
> - x86_pmu.flags |= PMU_FL_TFA;
> - x86_pmu.get_event_constraints = tfa_get_event_constraints;
> - x86_pmu.enable_all = intel_tfa_pmu_enable_all;
> - x86_pmu.commit_scheduling = intel_tfa_commit_scheduling;
> + u64 msr;
> +
> + rdmsrl(MSR_TSX_FORCE_ABORT, msr);
> + /* Systems that enumerate CPUID.RTM_ALWAYS_ABORT or
> + * support MSR_TSX_FORCE_ABORT[SDV_ENABLE_RTM] bit have
> + * TSX deprecated by default. TSX force abort hooks are
> + * not required on these systems.
So if they're not required, why aren't you simply disabling the force
abort "workaround" by clearing the feature flag?
if (boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) {
if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT))
setup_clear_cpu_cap(X86_FEATURE_TSX_FORCE_ABORT);
}
so that it doesn't get enabled in the first place?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
