[PATCH 3.12 42/84] arm64: KVM: Disable virtual timer even if the guest is not using it

[Jiri Slaby]

From: Marc Zyngier <marc.zyngier@xxxxxxx>

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

===============

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@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 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 a255167baf6a..44b00eb7b340 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -472,8 +472,6 @@ __kvm_hyp_code_start:
 	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
 
@@ -481,6 +479,9 @@ __kvm_hyp_code_start:
 	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
-- 
2.6.0

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