[PATCH v4 06/11] KVM: arm/arm64: use vcpu requests for power_off

Andrew Jones
2017-05-16T02:20:30Z

System shutdown is currently using request-less VCPU kicks. This
leaves open a tiny race window, as it doesn't ensure the state
change to power_off is seen by a VCPU just about to enter guest
mode. VCPU requests, OTOH, are guaranteed to be seen (see "Ensuring
Requests Are Seen" of Documentation/virtual/kvm/vcpu-requests.rst)
This patch applies the EXIT request used by pause to power_off,
fixing the race.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
virt/kvm/arm/psci.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index f68be2cc6256..f189d0ad30d5 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -179,10 +179,9 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
* after this call is handled and before the VCPUs have been
* re-initialized.
*/
- kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
+ kvm_for_each_vcpu(i, tmp, vcpu->kvm)
tmp->arch.power_off = true;
- kvm_vcpu_kick(tmp);
- }
+ kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_VCPU_EXIT);

memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
vcpu->run->system_event.type = type;
--
2.9.3