From 8f1aeaa46db8885546b10b8b25f5d0450593f356 Mon Sep 17 00:00:00 2001 From: Scott Wood Date: Wed, 22 Aug 2012 15:03:50 +0000 Subject: [PATCH] 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 Signed-off-by: Alexander Graf --- 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 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; } -- 2.39.5