KVM: arm/arm64: arch_timer: Preserve physical dist. active state on LR.active

We were incorrectly removing the active state from the physical
distributor on the timer interrupt when the timer output level was
deasserted.  We shouldn't be doing this without considering the virtual
interrupt's active state, because the architecture requires that when an
LR has the HW bit set and the pending or active bits set, then the
physical interrupt must also have the corresponding bits set.

This addresses an issue where we have been observing an inconsistency
between the LR state and the physical distributor state where the LR
state was active and the physical distributor was not active, which
shouldn't happen.

Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 17 insertions, 11 deletions

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 21a0ab2d8919..69bca185c471 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -221,17 +221,23 @@ void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
 	kvm_timer_update_state(vcpu);
 
 	/*
-	 * If we enter the guest with the virtual input level to the VGIC
-	 * asserted, then we have already told the VGIC what we need to, and
-	 * we don't need to exit from the guest until the guest deactivates
-	 * the already injected interrupt, so therefore we should set the
-	 * hardware active state to prevent unnecessary exits from the guest.
-	 *
-	 * Conversely, if the virtual input level is deasserted, then always
-	 * clear the hardware active state to ensure that hardware interrupts
-	 * from the timer triggers a guest exit.
-	 */
-	if (timer->irq.level)
+	* If we enter the guest with the virtual input level to the VGIC
+	* asserted, then we have already told the VGIC what we need to, and
+	* we don't need to exit from the guest until the guest deactivates
+	* the already injected interrupt, so therefore we should set the
+	* hardware active state to prevent unnecessary exits from the guest.
+	*
+	* Also, if we enter the guest with the virtual timer interrupt active,
+	* then it must be active on the physical distributor, because we set
+	* the HW bit and the guest must be able to deactivate the virtual and
+	* physical interrupt at the same time.
+	*
+	* Conversely, if the virtual input level is deasserted and the virtual
+	* interrupt is not active, then always clear the hardware active state
+	* to ensure that hardware interrupts from the timer triggers a guest
+	* exit.
+	*/
+	if (timer->irq.level || kvm_vgic_map_is_active(vcpu, timer->map))
 		phys_active = true;
 	else
 		phys_active = false;