arm64: KVM: Disable virtual timer even if the guest is not using it

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.

Cc: stable@vger.kernel.org
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 39aa322765f9fd8db6ab411131f2fce51d7e9429..60a83e2900a7bbe54d9266d2e85d832bc5300608 100644 (file)
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -562,8 +562,6 @@
        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
 
@@ -571,6 +569,9 @@
        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