linux-kernel - [PATCH v4 03/11] perf/x86/lbr: Skip checking for the existence of LBR

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Date:   Sun, 14 Mar 2021 23:52:16 +0800
From:   Like Xu <like.xu@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        x86@...nel.org, wei.w.wang@...el.com, linux-kernel@...r.kernel.org,
        Like Xu <like.xu@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v4 03/11] perf/x86/lbr: Skip checking for the existence of LBR_TOS for Arch LBR

The Architecture LBR does not have MSR_LBR_TOS (0x000001c9). KVM will
generate #GP for this MSR access, thereby preventing the initialization
of the guest LBR.

Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Ingo Molnar <mingo@...hat.com>
Fixes: 47125db27e47 ("perf/x86/intel/lbr: Support Architectural LBR")
Signed-off-by: Like Xu <like.xu@...ux.intel.com>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/events/intel/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 7bb96ac87615..0338e354826d 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5568,7 +5568,8 @@ __init int intel_pmu_init(void)
 	 * Check all LBR MSR here.
 	 * Disable LBR access if any LBR MSRs can not be accessed.
 	 */
-	if (x86_pmu.lbr_nr && !check_msr(x86_pmu.lbr_tos, 0x3UL))
+	if (x86_pmu.lbr_nr && !boot_cpu_has(X86_FEATURE_ARCH_LBR) &&
+	    !check_msr(x86_pmu.lbr_tos, 0x3UL))
 		x86_pmu.lbr_nr = 0;
 	for (i = 0; i < x86_pmu.lbr_nr; i++) {
 		if (!(check_msr(x86_pmu.lbr_from + i, 0xffffUL) &&
-- 
2.29.2