Commit 5bd1cf11 authored by Scott Wood's avatar Scott Wood Committed by Alexander Graf

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
......@@ -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;
}
......
......@@ -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;
}
......
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