[PATCH v3 06/10] KVM: arm/arm64: use vcpu requests for power_off

Andrew Jones
2017-05-03T16:06:31Z

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,
closing the race window and also allowing us to remove the final
check of power_off in VCPU RUN, as the final check for requests
is sufficient.

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

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 7be0d9b0c63a..26d9d4d72853 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -670,8 +670,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
smp_store_mb(vcpu->mode, IN_GUEST_MODE);

if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
- kvm_request_pending(vcpu) ||
- vcpu->arch.power_off) {
+ kvm_request_pending(vcpu)) {
vcpu->mode = OUTSIDE_GUEST_MODE;
local_irq_enable();
kvm_pmu_sync_hwstate(vcpu);
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index f68be2cc6256..f189d0ad30d5 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/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