From: Christoffer Dall <christoffer.dall@linaro.org>
Date: Sun, 29 Oct 2017 02:04:55 +0100
Subject: arm/arm64: KVM: Load the timer state when enabling the timer
Patch-mainline: v4.15-rc1
Git-commit: 4a2c4da1250d09c1477eff8e14a82b2573481f32
References: bsc#1077761

After being lazy with saving/restoring the timer state, we defer that
work to vcpu_load and vcpu_put, which ensure that the timer state is
loaded on the hardware timers whenever the VCPU runs.

Unfortunately, we are failing to do that the first time vcpu_load()
runs, because the timer has not yet been enabled at that time.  As long
as the initialized timer state matches what happens to be in the
hardware (a disabled timer, because we never leave the timer screaming),
this does not show up as a problem, but is nevertheless incorrect.

The solution is simple; disable preemption while setting the timer to be
enabled, and call the timer load function when first enabling the timer.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Alexander Graf <agraf@suse.de>
---
 virt/kvm/arm/arch_timer.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -861,7 +861,11 @@
 		return ret;
 
 no_vgic:
+	preempt_disable();
 	timer->enabled = 1;
+	kvm_timer_vcpu_load_vgic(vcpu);
+	preempt_enable();
+
 	return 0;
 }