linux-kernel - [PATCH 11/11] KVM: x86/pmu: Protect kvm->arch.pmu_event

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Message-Id: <20220221115201.22208-12-likexu@tencent.com>
Date:   Mon, 21 Feb 2022 19:52:01 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Like Xu <likexu@...cent.com>
Subject: [PATCH 11/11] KVM: x86/pmu: Protect kvm->arch.pmu_event_filter with SRCU

From: Like Xu <likexu@...cent.com>

Similar to "kvm->arch.msr_filter", KVM should guarantee that vCPUs will
see either the previous filter or the new filter when user space calls
KVM_SET_PMU_EVENT_FILTER ioctl with the vCPU running so that guest
pmu events with identical settings in both the old and new filter have
deterministic behavior.

Fixes: 66bb8a065f5a ("KVM: x86: PMU Event Filter")
Signed-off-by: Like Xu <likexu@...cent.com>
Reviewed-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kvm/pmu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 40a6e778b3d9..84f0fcbba820 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -183,11 +183,12 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc)
 	struct kvm *kvm = pmc->vcpu->kvm;
 	bool allow_event = true;
 	__u64 key;
-	int idx;
+	int idx, srcu_idx;
 
 	if (kvm_x86_ops.pmu_ops->hw_event_is_unavail(pmc))
 		return false;
 
+	srcu_idx = srcu_read_lock(&kvm->srcu);
 	filter = srcu_dereference(kvm->arch.pmu_event_filter, &kvm->srcu);
 	if (!filter)
 		goto out;
@@ -210,6 +211,7 @@ static bool check_pmu_event_filter(struct kvm_pmc *pmc)
 	}
 
 out:
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
 	return allow_event;
 }
 
-- 
2.35.0