[PATCH 3.13.y-ckt 25/48] arm: KVM: Disable virtual timer even if the guest is not using it

[Kamal Mostafa]

3.13.11-ckt29 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <marc.zyngier at arm.com>

commit 688bc577ac42ae3d07c889a1f0a72f0b23763d58 upstream.

When running a guest with the architected timer disabled (with QEMU and
the kernel_irqchip=off option, for example), it is important to make
sure the timer gets turned off. Otherwise, the guest may try to
enable it anyway, leading to a screaming HW interrupt.

The fix is to unconditionally turn off the virtual timer on guest
exit.

Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm/kvm/interrupts_head.S | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
index b6f6137..2ec794d 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -494,8 +494,7 @@ vcpu	.req	r0		@ vcpu pointer always in r0
 
 	mrc	p15, 0, r2, c14, c3, 1	@ CNTV_CTL
 	str	r2, [vcpu, #VCPU_TIMER_CNTV_CTL]
-	bic	r2, #1			@ Clear ENABLE
-	mcr	p15, 0, r2, c14, c3, 1	@ CNTV_CTL
+
 	isb
 
 	mrrc	p15, 3, r2, r3, c14	@ CNTV_CVAL
@@ -508,6 +507,9 @@ vcpu	.req	r0		@ vcpu pointer always in r0
 	mcrr	p15, 4, r2, r2, c14	@ CNTVOFF
 
 1:
+	mov	r2, #0			@ Clear ENABLE
+	mcr	p15, 0, r2, c14, c3, 1	@ CNTV_CTL
+
 #endif
 	@ Allow physical timer/counter access for the host
 	mrc	p15, 4, r2, c14, c1, 0	@ CNTHCTL
-- 
1.9.1