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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 <mlevitsk@redhat.com>
Message-Id: <20220606180829.102503-7-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Maxim Levitsky 2022-06-06 21:08:28 +03:00 committed by Paolo Bonzini
parent 66c768d30e
commit 18869f26df
1 changed files with 6 additions and 2 deletions
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8
virt/kvm/kvm_main.c
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@ -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;