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Subject[PATCH 3.19.y-ckt 39/86] arm64: KVM: Disable virtual timer even if the guest is not using it
Date
3.19.8-ckt9 -stable review patch.  If anyone has any objections, please let me know.

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

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: Kamal Mostafa <kamal@canonical.com>
---
arch/arm64/kvm/hyp.S | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index cbaa8bc..0a2ff0f 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -843,8 +843,6 @@
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

@@ -852,6 +850,9 @@
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
--
1.9.1


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