[PATCH] KVM: VMX: fix halt emulation while emulating invalid guest sate

[PATCH] KVM: VMX: fix halt emulation while emulating invalid guest sate

[Gleb Natapov]

The invalid guest state emulation loop does not check halt_request
which causes 100% cpu loop while guest is in halt and in invalid
state, but more serious issue is that this leaves halt_request set, so
random instruction emulated by vm86 #GP exit can be interpreted
as halt which causes guest hang. Fix both problems by handling
halt_request in emulation loop.

Reported-by: Tomas Papan <tomas.papan@gmail.com>
Tested-by: Tomas Papan <tomas.papan@gmail.com>
CC: stable@vger.kernel.org
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5a87a58..a9fa4bc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5312,6 +5312,12 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 			return 0;
 		}
 
+		if (vcpu->arch.halt_request) {
+			vcpu->arch.halt_request = 0;
+			ret = kvm_emulate_halt(vcpu);
+			goto out;
+		}
+
 		if (signal_pending(current))
 			goto out;
 		if (need_resched())
--
			Gleb.

Re: [PATCH] KVM: VMX: fix halt emulation while emulating invalid guest sate

[Paolo Bonzini]

----- Messaggio originale -----
> Da: "Gleb Natapov" <gleb@redhat.com>
> A: kvm@vger.kernel.org
> Cc: pbonzini@redhat.com, stable@vger.kernel.org
> Inviato: Mercoledì, 8 maggio 2013 17:38:44
> Oggetto: [PATCH] KVM: VMX: fix halt emulation while emulating invalid guest sate
> 
> The invalid guest state emulation loop does not check halt_request
> which causes 100% cpu loop while guest is in halt and in invalid
> state, but more serious issue is that this leaves halt_request set, so
> random instruction emulated by vm86 #GP exit can be interpreted
> as halt which causes guest hang. Fix both problems by handling
> halt_request in emulation loop.
> 
> Reported-by: Tomas Papan <tomas.papan@gmail.com>
> Tested-by: Tomas Papan <tomas.papan@gmail.com>
> CC: stable@vger.kernel.org
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 5a87a58..a9fa4bc 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5312,6 +5312,12 @@ static int handle_invalid_guest_state(struct kvm_vcpu
> *vcpu)
>  			return 0;
>  		}
>  
> +		if (vcpu->arch.halt_request) {
> +			vcpu->arch.halt_request = 0;
> +			ret = kvm_emulate_halt(vcpu);
> +			goto out;
> +		}
> +
>  		if (signal_pending(current))
>  			goto out;
>  		if (need_resched())
> --
> 			Gleb.
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>