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Commit 5bd1cf11 authored by Scott Wood's avatar Scott Wood Committed by Alexander Graf
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KVM: PPC: set IN_GUEST_MODE before checking requests 



Avoid a race as described in the code comment.

Also remove a related smp_wmb() from booke's kvmppc_prepare_to_enter().
I can't see any reason for it, and the book3s_pr version doesn't have it.

Signed-off-by: default avatarScott Wood <scottwood@freescale.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
parent adbb48a8

arch/powerpc/kvm/booke.c

+0 −1
Original line number Diff line number Diff line
@@ -674,7 +674,6 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) 


out:

	vcpu->mode = OUTSIDE_GUEST_MODE;

	smp_wmb();

	return ret;

}

arch/powerpc/kvm/powerpc.c

+9 −5
Original line number Diff line number Diff line
@@ -78,7 +78,16 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) 
			break;

		}



		vcpu->mode = IN_GUEST_MODE;



		/*

		 * Reading vcpu->requests must happen after setting vcpu->mode,

		 * so we don't miss a request because the requester sees

		 * OUTSIDE_GUEST_MODE and assumes we'll be checking requests

		 * before next entering the guest (and thus doesn't IPI).

		 */

		smp_mb();



		if (vcpu->requests) {

			/* Make sure we process requests preemptable */

			local_irq_enable();
@@ -111,11 +120,6 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) 
#endif



		kvm_guest_enter();



		/* Going into guest context! Yay! */

		vcpu->mode = IN_GUEST_MODE;

		smp_wmb();



		break;

	}