Messages in this thread | | | Date | Fri, 11 Jun 2021 09:50:22 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 2/4] perf/x86/intel: Do not deploy workaround when TSX is deprecated |
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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@linux.intel.com> > Reviewed-by: Andi Kleen <ak@linux.intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > Tested-by: Neelima Krishnan <neelima.krishnan@intel.com> > --- > 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
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