[PATCH v2 5/6] arm/arm64: KVM: Turn off vcpus on PSCI shutdown/reboot

Christoffer Dall christoffer.dall at linaro.org
Wed Dec 3 13:18:41 PST 2014

When a vcpu calls SYSTEM_OFF or SYSTEM_RESET with PSCI v0.2, the vcpus
should really be turned off for the VM adhering to the suggestions in
the PSCI spec, and it's the sane thing to do.

Also, clarify the behavior and expectations for exits to user space with

Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
 Documentation/virtual/kvm/api.txt |  9 +++++++++
 arch/arm/kvm/psci.c               | 19 +++++++++++++++++++
 arch/arm64/include/asm/kvm_host.h |  1 +
 3 files changed, 29 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 81f1b97..228f9cf 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2957,6 +2957,15 @@ HVC instruction based PSCI call from the vcpu. The 'type' field describes
 the system-level event type. The 'flags' field describes architecture
 specific flags for the system-level event.
+Valid values for 'type' are:
+  KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
+   VM. Userspace is not obliged to honour this, and if it does honour
+   this does not need to destroy the VM synchronously (ie it may call
+   KVM_RUN again before shutdown finally occurs).
+  KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
+   As with SHUTDOWN, userspace can choose to ignore the request, or
+   to schedule the reset to occur in the future and may call KVM_RUN again.
 		/* Fix the size of the union. */
 		char padding[256];
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index 09cf377..ae0bb91 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -15,6 +15,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#include <linux/preempt.h>
 #include <linux/kvm_host.h>
 #include <linux/wait.h>
@@ -166,6 +167,24 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
+	int i;
+	struct kvm_vcpu *tmp;
+	/*
+	 * The KVM ABI specifies that a system event exit may call KVM_RUN
+	 * again and may perform shutdown/reboot at a later time that when the
+	 * actual request is made.  Since we are implementing PSCI and a
+	 * caller of PSCI reboot and shutdown expects that the system shuts
+	 * down or reboots immediately, let's make sure that VCPUs are not run
+	 * after this call is handled and before the VCPUs have been
+	 * re-initialized.
+	 */
+	kvm_for_each_vcpu(i, tmp, vcpu->kvm)
+		tmp->arch.pause = true;
+	preempt_disable();
+	force_vm_exit(cpu_all_mask);
+	preempt_enable();
 	memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 	vcpu->run->system_event.type = type;
 	vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 65c6152..0b7dfdb 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -198,6 +198,7 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
 struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);
 u64 kvm_call_hyp(void *hypfn, ...);
+void force_vm_exit(const cpumask_t *mask);
 int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		int exception_index);

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