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

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


>From 27e91ad1e746e341ca2312f29bccb9736be7b476 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
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 <marc.zyngier@arm.com>

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.

Cc: stable@vger.kernel.org
Fixes: f68d2b1b73cc ("arm64: KVM: Implement vgic-v3 save/restore")
Acked-by: Christoffer Dall <cdall@kernel.org>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/virt/kvm/arm/hyp/vgic-v3-sr.c
+++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
@@ -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 marc.zyngier@arm.com 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