[PATCH 3.19.y-ckt 40/86] arm: KVM: Disable virtual timer even if the guest is not using it

From: Kamal Mostafa
Date: Tue Oct 27 2015 - 18:05:14 EST


3.19.8-ckt9 -stable review patch. If anyone has any objections, please let me know.

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

From: Marc Zyngier <marc.zyngier@xxxxxxx>

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@xxxxxxx>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
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 f6f1481..1fb756e 100644
--- a/arch/arm/kvm/interrupts_head.S
+++ b/arch/arm/kvm/interrupts_head.S
@@ -523,8 +523,7 @@ ARM_BE8(rev r6, r6 )

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, rr_lo_hi(r2, r3), c14 @ CNTV_CVAL
@@ -537,6 +536,9 @@ ARM_BE8(rev r6, r6 )
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

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