Patch "arm64: KVM: Disable virtual timer even if the guest is not using it" has been added to the 4.1-stable tree

Patch "arm64: KVM: Disable virtual timer even if the guest is not using it" has been added to the 4.1-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-kvm-disable-virtual-timer-even-if-the-guest-is-not-using-it.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From c4cbba9fa078f55d9f6d081dbb4aec7cf969e7c7 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Wed, 16 Sep 2015 16:18:59 +0100
Subject: arm64: KVM: Disable virtual timer even if the guest is not using it

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


Patches currently in stable-queue which might be from marc.zyngier@arm.com are

queue-4.1/arm64-head.s-initialise-mdcr_el2-in-el2_setup.patch
queue-4.1/kvm-arm64-add-workaround-for-cortex-a57-erratum-852523.patch
queue-4.1/arm64-kvm-disable-virtual-timer-even-if-the-guest-is-not-using-it.patch
queue-4.1/arm-arm64-kvm-vgic-check-for-irqchip_in_kernel-when-mapping-resources.patch