[PATCH 2/2] arm/arm64: KVM: arch timer: Reset CNTV_CTL to 0

[Christoffer Dall]

Provide a better quality of implementation and be architecture compliant
on ARMv7 for the architected timer by resetting the CNTV_CTL to 0 on
reset of the timer, and call kvm_timer_update_state(vcpu) at the same
time, ensuring the timer output is not asserted after, for example, a
PSCI system reset.

This change alone fixes the UEFI reset issue reported by Laszlo back in
February.

Cc: Laszlo Ersek <lersek at redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
Cc: Drew Jones <drjones at redhat.com>
Cc: Wei Huang <wei at redhat.com>
Cc: Peter Maydell <peter.maydell at linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---
 virt/kvm/arm/arch_timer.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 76e38d2..48c6e1a 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -200,6 +200,14 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
 	timer->irq = irq;
 
 	/*
+	 * The bits in CNTV_CTL are architecturally reset to UNKNOWN for ARMv8
+	 * and to 0 for ARMv7.  We provide an implementation that always
+	 * resets the timer to be disabled and unmasked and is compliant with
+	 * the ARMv7 architecture.
+	 */
+	timer->cntv_ctl = 0;
+
+	/*
 	 * Tell the VGIC that the virtual interrupt is tied to a
 	 * physical interrupt. We do that once per VCPU.
 	 */
-- 
2.1.2.330.g565301e.dirty