ARM: KVM: arch_timers: zero CNTVOFF upon return to host

To use the virtual counters from the host, we need to ensure that
CNTVOFF doesn't change unexpectedly. When we change to a guest, we
replace the host's CNTVOFF, but we don't restore it when returning to
the host.

As the host sets CNTVOFF to zero, and never changes it, we can simply
zero CNTVOFF when returning to the host. This patch adds said zeroing to
the return to host path.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Christoffer Dall <cdall@cs.columbia.edu>

diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index 3c8f2f0b4c5e105c765b281241415066ce1470d2..d43cfb5b37c4baaa360268add101314419b3f58e 100644 (file)
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -497,6 +497,10 @@ vcpu       .req    r0              @ vcpu pointer always in r0
        add     r5, vcpu, r4
        strd    r2, r3, [r5]
 
+       @ Ensure host CNTVCT == CNTPCT
+       mov     r2, #0
+       mcrr    p15, 4, r2, r2, c14     @ CNTVOFF
+
 1:
 #endif
        @ Allow physical timer/counter access for the host