KVM: arm64: Only open the interrupt window on exit due to an interrupt

Now that we properly account for interrupts taken whilst the guest
was running, it becomes obvious that there is no need to open
this accounting window if we didn't exit because of an interrupt.

This saves a number of system register accesses and other barriers
if we exited for any other reason (such as a trap, for example).

Signed-off-by: Marc Zyngier <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index ecc5958e27fe..5254a97929f7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -945,9 +945,11 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		 * context synchronization event) is necessary to ensure that
 		 * pending interrupts are taken.
 		 */
-		local_irq_enable();
-		isb();
-		local_irq_disable();
+		if (ARM_EXCEPTION_CODE(ret) == ARM_EXCEPTION_IRQ) {
+			local_irq_enable();
+			isb();
+			local_irq_disable();
+		}
 
 		guest_timing_exit_irqoff();