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KVM: PPC: set IN_GUEST_MODE before checking requests

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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: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
Scott Wood 2012-08-22 15:03:50 +00:00 committed by Alexander Graf
parent adbb48a854
commit 5bd1cf1185
2 changed files with 9 additions and 6 deletions
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1
arch/powerpc/kvm/booke.c
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@ -674,7 +674,6 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
out: out:
vcpu->mode = OUTSIDE_GUEST_MODE; vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
return ret; return ret;
} }

14
arch/powerpc/kvm/powerpc.c
View File

@ -78,7 +78,16 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
break; 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(); smp_mb();
if (vcpu->requests) { if (vcpu->requests) {
/* Make sure we process requests preemptable */ /* Make sure we process requests preemptable */
local_irq_enable(); local_irq_enable();
@ -111,11 +120,6 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
#endif #endif
kvm_guest_enter(); kvm_guest_enter();
/* Going into guest context! Yay! */
vcpu->mode = IN_GUEST_MODE;
smp_wmb();
break; break;
} }