From: Scott Wood <scottw...@freescale.com>

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 <scottw...@freescale.com>
Signed-off-by: Alexander Graf <ag...@suse.de>
---
 arch/powerpc/kvm/booke.c   |    1 -
 arch/powerpc/kvm/powerpc.c |   14 +++++++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 69d047c..3d1f35d 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 6002ea9..deb0d59 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;
        }
 
-- 
1.6.0.2

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