linux-kernel - [PATCH] KVM: vPMU: Use atomic bit operations for global

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Message-ID: <20230911061147.409152-1-mizhang@google.com>
Date:   Mon, 11 Sep 2023 06:11:47 +0000
From:   Mingwei Zhang <mizhang@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>,
        Dapeng Mi <dapeng1.mi@...el.com>,
        Jim Mattson <jmattson@...gle.com>, Like Xu <likexu@...cent.com>
Subject: [PATCH] KVM: vPMU: Use atomic bit operations for global_status

Use atomic bit operations for pmu->global_status because it may suffer from
race conditions between emulated overflow in KVM vPMU and PEBS overflow in
host PMI handler.

Fixes: f331601c65ad ("KVM: x86/pmu: Don't generate PEBS records for emulated instructions")
Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 arch/x86/kvm/pmu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index edb89b51b383..00b48f25afdb 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -117,11 +117,11 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi)
 			skip_pmi = true;
 		} else {
 			/* Indicate PEBS overflow PMI to guest. */
-			skip_pmi = __test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT,
-						      (unsigned long *)&pmu->global_status);
+			skip_pmi = test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT,
+						    (unsigned long *)&pmu->global_status);
 		}
 	} else {
-		__set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
+		set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
 	}
 
 	if (!pmc->intr || skip_pmi)

base-commit: e2013f46ee2e721567783557c301e5c91d0b74ff
-- 
2.42.0.283.g2d96d420d3-goog