[PATCH v2 1/7] KVM: arm64: Move OUTSIDE_GUEST_MODE publication past context being saved

[Marc Zyngier]

OUTSIDE_GUEST_MODE indicates to the rest of KVM that the vcpu has
exited. So far, this is set as soon as we return from the notional
hypervisor (which with VHE is just a function call away).

However, code that uses OUTSIDE_GUEST_MODE as a synchronisation point
relies on the vcpu state to have been written back to the in-memory
structures. Clearly, this is not what is happening

Move the publication of OUTSIDE_GUEST_MODE to the point where the state
is actually written, and give this write release semantics to ensure the
correct ordering.

Signed-off-by: Marc Zyngier <maz at kernel.org>
Cc: stable at vger.kernel.org
---
 arch/arm64/kvm/arm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 8b080804bc90b..5f5dd8bead4b9 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1352,7 +1352,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
 		ret = kvm_arm_vcpu_enter_exit(vcpu);
 
-		vcpu->mode = OUTSIDE_GUEST_MODE;
 		vcpu->stat.exits++;
 		/*
 		 * Back from guest
@@ -1386,6 +1385,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
 		kvm_arch_vcpu_ctxsync_fp(vcpu);
 
+		/*
+		 * All the state has been synchronised, let advertise
+		 * we're outside of the guest.
+		 */
+		smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE);
+
 		/*
 		 * We must ensure that any pending interrupts are taken before
 		 * we exit guest timing so that timer ticks are accounted as
-- 
2.47.3