From b0380e13502adf7dd8be4c47d622c3522aae6c63 Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Thu, 14 Jul 2022 11:26:30 -0700 Subject: perf/x86/intel/lbr: Fix unchecked MSR access error on HSW The fuzzer triggers the below trace. [ 7763.384369] unchecked MSR access error: WRMSR to 0x689 (tried to write 0x1fffffff8101349e) at rIP: 0xffffffff810704a4 (native_write_msr+0x4/0x20) [ 7763.397420] Call Trace: [ 7763.399881] [ 7763.401994] intel_pmu_lbr_restore+0x9a/0x1f0 [ 7763.406363] intel_pmu_lbr_sched_task+0x91/0x1c0 [ 7763.410992] __perf_event_task_sched_in+0x1cd/0x240 On a machine with the LBR format LBR_FORMAT_EIP_FLAGS2, when the TSX is disabled, a TSX quirk is required to access LBR from registers. The lbr_from_signext_quirk_needed() is introduced to determine whether the TSX quirk should be applied. However, the lbr_from_signext_quirk_needed() is invoked before the intel_pmu_lbr_init(), which parses the LBR format information. Without the correct LBR format information, the TSX quirk never be applied. Move the lbr_from_signext_quirk_needed() into the intel_pmu_lbr_init(). Checking x86_pmu.lbr_has_tsx in the lbr_from_signext_quirk_needed() is not required anymore. Both LBR_FORMAT_EIP_FLAGS2 and LBR_FORMAT_INFO have LBR_TSX flag, but only the LBR_FORMAT_EIP_FLAGS2 requirs the quirk. Update the comments accordingly. Fixes: 1ac7fd8159a8 ("perf/x86/intel/lbr: Support LBR format V7") Reported-by: Vince Weaver Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20220714182630.342107-1-kan.liang@linux.intel.com --- arch/x86/events/intel/lbr.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c index 13179f31fe10..4f70fb6c2c1e 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -278,9 +278,9 @@ enum { }; /* - * For formats with LBR_TSX flags (e.g. LBR_FORMAT_EIP_FLAGS2), bits 61:62 in - * MSR_LAST_BRANCH_FROM_x are the TSX flags when TSX is supported, but when - * TSX is not supported they have no consistent behavior: + * For format LBR_FORMAT_EIP_FLAGS2, bits 61:62 in MSR_LAST_BRANCH_FROM_x + * are the TSX flags when TSX is supported, but when TSX is not supported + * they have no consistent behavior: * * - For wrmsr(), bits 61:62 are considered part of the sign extension. * - For HW updates (branch captures) bits 61:62 are always OFF and are not @@ -288,7 +288,7 @@ enum { * * Therefore, if: * - * 1) LBR has TSX format + * 1) LBR format LBR_FORMAT_EIP_FLAGS2 * 2) CPU has no TSX support enabled * * ... then any value passed to wrmsr() must be sign extended to 63 bits and any @@ -300,7 +300,7 @@ static inline bool lbr_from_signext_quirk_needed(void) bool tsx_support = boot_cpu_has(X86_FEATURE_HLE) || boot_cpu_has(X86_FEATURE_RTM); - return !tsx_support && x86_pmu.lbr_has_tsx; + return !tsx_support; } static DEFINE_STATIC_KEY_FALSE(lbr_from_quirk_key); @@ -1609,9 +1609,6 @@ void intel_pmu_lbr_init_hsw(void) x86_pmu.lbr_sel_map = hsw_lbr_sel_map; x86_get_pmu(smp_processor_id())->task_ctx_cache = create_lbr_kmem_cache(size, 0); - - if (lbr_from_signext_quirk_needed()) - static_branch_enable(&lbr_from_quirk_key); } /* skylake */ @@ -1702,7 +1699,11 @@ void intel_pmu_lbr_init(void) switch (x86_pmu.intel_cap.lbr_format) { case LBR_FORMAT_EIP_FLAGS2: x86_pmu.lbr_has_tsx = 1; - fallthrough; + x86_pmu.lbr_from_flags = 1; + if (lbr_from_signext_quirk_needed()) + static_branch_enable(&lbr_from_quirk_key); + break; + case LBR_FORMAT_EIP_FLAGS: x86_pmu.lbr_from_flags = 1; break; -- cgit v1.2.3