Joerg Roedel wrote:
For KVM remote TLB flushes we need to check the KVM_REQ_TLB_FLUSH request flag when the irqs are already disabled. Otherwise there is a small window of time for a race condition where we may enter a guest without doing a requested TLB flush. @@ -3108,8 +3108,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) kvm_write_guest_time(vcpu); if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests)) kvm_mmu_sync_roots(vcpu); - if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests)) - kvm_x86_ops->tlb_flush(vcpu); if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS, &vcpu->requests)) { kvm_run->exit_reason = KVM_EXIT_TPR_ACCESS; @@ -3133,6 +3131,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)local_irq_disable(); + if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))+ kvm_x86_ops->tlb_flush(vcpu); + if (vcpu->requests || need_resched() || signal_pending(current)) { local_irq_enable(); preempt_enable();
If we lost the race and someone sets a bit after the test, then the test immediately above will pick this up retry the bit tests.
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