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    • Maxim Levitsky's avatar
      KVM: SVM: fix race between interrupt delivery and AVIC inhibition · 66fa226c
      Maxim Levitsky authored
      
      
      If svm_deliver_avic_intr is called just after the target vcpu's AVIC got
      inhibited, it might read a stale value of vcpu->arch.apicv_active
      which can lead to the target vCPU not noticing the interrupt.
      
      To fix this use load-acquire/store-release so that, if the target vCPU
      is IN_GUEST_MODE, we're guaranteed to see a previous disabling of the
      AVIC.  If AVIC has been disabled in the meanwhile, proceed with the
      KVM_REQ_EVENT-based delivery.
      
      Incomplete IPI vmexit has the same races as svm_deliver_avic_intr, and
      in fact it can be handled in exactly the same way; the only difference
      lies in who has set IRR, whether svm_deliver_interrupt or the processor.
      Therefore, svm_complete_interrupt_delivery can be used to fix incomplete
      IPI vmexits as well.
      
      Co-developed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
      Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
      66fa226c
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