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authorScott Wood <scottwood@freescale.com>2012-08-22 15:03:50 +0000
committerAlexander Graf <agraf@suse.de>2012-10-05 23:38:54 +0200
commit5bd1cf118533aba41b3fbd4834e6362a9237db71 (patch)
tree33cf8766cec82d210d95755a8291855c7f199705 /arch
parentadbb48a854bf8dee556dc42b96dd61503351a82d (diff)
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: Scott Wood <scottwood@freescale.com> Signed-off-by: Alexander Graf <agraf@suse.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kvm/booke.c1
-rw-r--r--arch/powerpc/kvm/powerpc.c14
2 files changed, 9 insertions, 6 deletions
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 69d047c22d20..3d1f35dc7862 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -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;
}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6002ea938a48..deb0d596d815 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -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;
}