[KVMTOOL][PATCH] Handle KVM_EXIT_SYSTEM_EVENT on any VCPU

[Mark Rutland <mark.rutland@arm.com>]

When VCPU #0 exits (e.g. due to KVM_EXIT_SYSTEM_EVENT), it sends
SIGKVMEXIT to all other VCPUs, waits for them to exit, then tears down
any remaining context. The signalling of SIGKVMEXIT is critical to
forcing VCPUs to shut down in response to a system event (e.g. PSCI
SYSTEM_OFF).

VCPUs other that VCPU #0 simply exit in kvm_cpu_thread without forcing
other CPUs to shut down. Thus if a system event is taken on a VCPU other
than VCPU #0, the remaining CPUs are left online. This results in KVM
tool not exiting as expected when a system event is taken on a VCPU
other than VCPU #0 (as may happen if the guest panics).

Fix this by signalling SIGKVMEXIT to VCPU #0 when a system event is
taken on other CPUs, so that it may tear things down as usual.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
---
 kvm-cpu.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kvm-cpu.c b/kvm-cpu.c
index 5d90664..f47e3db 100644
--- a/kvm-cpu.c
+++ b/kvm-cpu.c
@@ -166,13 +166,20 @@ int kvm_cpu__start(struct kvm_cpu *cpu)
 			 * treat all system events as shutdown request.
 			 */
 			switch (cpu->kvm_run->system_event.type) {
-			case KVM_SYSTEM_EVENT_RESET:
-				/* Fall through for now */
-			case KVM_SYSTEM_EVENT_SHUTDOWN:
-				goto exit_kvm;
 			default:
 				pr_warning("unknown system event type %d",
 					   cpu->kvm_run->system_event.type);
+				/* fall through for now */
+			case KVM_SYSTEM_EVENT_RESET:
+				/* Fall through for now */
+			case KVM_SYSTEM_EVENT_SHUTDOWN:
+				/*
+				 * Ensure that VCPU #0 tears everything down if
+				 * the event was taken on a different VCPU.
+				 */
+				if (cpu->cpu_id != 0)
+					pthread_kill(cpu->kvm->cpus[0]->thread,
+						     SIGKVMEXIT);
 				goto exit_kvm;
 			};
 			break;
-- 
1.9.1