[PATCH 3.13.y-ckt 24/48] arm64: KVM: Disable virtual timer even if the guest is not using it

From: Kamal Mostafa
Date: Tue Oct 27 2015 - 17:42:44 EST

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


From: Marc Zyngier <marc.zyngier@xxxxxxx>

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

Reviewed-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
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 3b47c36..a1621ff 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -485,8 +485,6 @@ CPU_BE( rev w5, w5 )
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


@@ -494,6 +492,9 @@ CPU_BE( rev w5, w5 )
str x3, [x0, #VCPU_TIMER_CNTV_CVAL]

+ // 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

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