KVM: x86: disable preemption while updating apicv inhibition

Currently nothing prevents preemption in kvm_vcpu_update_apicv.

On SVM, If the preemption happens after we update the
vcpu->arch.apicv_active, the preemption itself will
'update' the inhibition since the AVIC will be first disabled
on vCPU unload and then enabled, when the current task
is loaded again.

Then we will try to update it again, which will lead to a warning
in __avic_vcpu_load, that the AVIC is already enabled.

Fix this by disabling preemption in this code.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220606180829.102503-6-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 03fbfbbec460fab308dc3a490bf20c22d119ba39..158b2e135efce57d5b89e79e43dbdf283413d96a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9850,6 +9850,7 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
                return;
 
        down_read(&vcpu->kvm->arch.apicv_update_lock);
+       preempt_disable();
 
        activate = kvm_vcpu_apicv_activated(vcpu);
 
@@ -9870,6 +9871,7 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
                kvm_make_request(KVM_REQ_EVENT, vcpu);
 
 out:
+       preempt_enable();
        up_read(&vcpu->kvm->arch.apicv_update_lock);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_update_apicv);