Patch "kvm: arm/arm64: vgic-v3: Tighten synchronization for guests using v2 on v3" has been added to the 4.15-stable tree

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

kvm: arm/arm64: vgic-v3: Tighten synchronization for guests using v2 on v3

to the 4.15-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:
kvm-arm-arm64-vgic-v3-tighten-synchronization-for-guests-using-v2-on-v3.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marc Zyngier <[email protected]>
Date: Tue, 6 Mar 2018 21:44:37 +0000
Subject: kvm: arm/arm64: vgic-v3: Tighten synchronization for guests using v2 on v3

From: Marc Zyngier <[email protected]>

commit 27e91ad1e746e341ca2312f29bccb9736be7b476 upstream.

On guest exit, and when using GICv2 on GICv3, we use a dsb(st) to force synchronization between the memory-mapped guest view and the system-register view that the hypervisor uses.

This is incorrect, as the spec calls out the need for "a DSB whose required access type is both loads and stores with any Shareability attribute", while we're only synchronizing stores.

We also lack an isb after the dsb to ensure that the latter has actually been executed before we start reading stuff from the sysregs.

The fix is pretty easy: turn dsb(st) into dsb(sy), and slap an isb() just after.

---
 virt/kvm/arm/hyp/vgic-v3-sr.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -215,7 +215,8 @@ void __hyp_text __vgic_v3_save_state(str
 	 * are now visible to the system register interface.
 	 */
 	if (!cpu_if->vgic_sre) {
-		dsb(st);
+		dsb(sy);
+		isb();
 		cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2);
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/kvm-arm-arm64-vgic-don-t-populate-multiple-lrs-with-the-same-vintid.patch queue-4.15/kvm-arm-arm64-vgic-v3-tighten-synchronization-for-guests-using-v2-on-v3.patch queue-4.15/kvm-arm-arm64-reset-mapped-irqs-on-vm-reset.patch queue-4.15/kvm-arm-arm64-reduce-verbosity-of-kvm-init-log.patch