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- Reorganize the perf LBR init code so that a TSX quirk is applied early

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enough in order for the LBR MSR access to not #GP
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Merge tag 'perf_urgent_for_v5.19_rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull perf fix from Borislav Petkov:

 - Reorganize the perf LBR init code so that a TSX quirk is applied
   early enough in order for the LBR MSR access to not #GP

* tag 'perf_urgent_for_v5.19_rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel/lbr: Fix unchecked MSR access error on HSW
This commit is contained in:
Linus Torvalds 2022-07-24 09:55:53 -07:00
commit af2c9ac240
1 changed files with 10 additions and 9 deletions
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19
arch/x86/events/intel/lbr.c
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@ -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;