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>
(cherry picked from commit f793c23ebbe5afd1cabf4a42a3a297022213756f)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index 2b44b95a86ddf6e77d60b6d28ef1de954d3236c6..6f18695a09cb5b50d8d849c9f2b486e8a01529c9 100644 (file)
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -503,6 +503,10 @@ 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