From 18869f26df1a11ed11031dfb7392bc7d774062e8 Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Mon, 6 Jun 2022 21:08:28 +0300 Subject: [PATCH] KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking On SVM, if preemption happens right after the call to finish_rcuwait but before call to kvm_arch_vcpu_unblocking on SVM/AVIC, it itself will re-enable AVIC, and then we will try to re-enable it again in kvm_arch_vcpu_unblocking which will lead to a warning in __avic_vcpu_load. The same problem can happen if the vCPU is preempted right after the call to kvm_arch_vcpu_blocking but before the call to prepare_to_rcuwait and in this case, we will end up with AVIC enabled during sleep - Ooops. Signed-off-by: Maxim Levitsky Message-Id: <20220606180829.102503-7-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 44c47670447a..a49df8988cd6 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3328,9 +3328,11 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu) vcpu->stat.generic.blocking = 1; + preempt_disable(); kvm_arch_vcpu_blocking(vcpu); - prepare_to_rcuwait(wait); + preempt_enable(); + for (;;) { set_current_state(TASK_INTERRUPTIBLE); @@ -3340,9 +3342,11 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu) waited = true; schedule(); } - finish_rcuwait(wait); + preempt_disable(); + finish_rcuwait(wait); kvm_arch_vcpu_unblocking(vcpu); + preempt_enable(); vcpu->stat.generic.blocking = 0;