arm/arm64: KVM: arch timer: Reset CNTV_CTL to 0

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.

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

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Drew Jones <drjones@redhat.com>
Cc: Wei Huang <wei@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

virt/kvm/arm/arch_timer.c

@@ -199,6 +199,14 @@ 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.