[PATCH 4.1 025/159] arm64: KVM: Disable virtual timer even if the guest is not using it

Greg Kroah-Hartman
2015-09-26T21:11:25Z

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

commit c4cbba9fa078f55d9f6d081dbb4aec7cf969e7c7 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.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/kvm/hyp.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -844,8 +844,6 @@
mrs x3, cntv_ctl_el0
and x3, x3, #3
str w3, [x0, #VCPU_TIMER_CNTV_CTL]
- bic x3, x3, #1 // Clear Enable
- msr cntv_ctl_el0, x3

isb

@@ -853,6 +851,9 @@
str x3, [x0, #VCPU_TIMER_CNTV_CVAL]

1:
+ // Disable the virtual timer
+ msr cntv_ctl_el0, xzr
+
// Allow physical timer/counter access for the host
mrs x2, cnthctl_el2
orr x2, x2, #3