tree 6d1d6c91a2995b6c30eac4a480204f126600a2c8
parent 2ffe95e3aa1eb309026b9948ac74e2d509d27c26
author Marc Zyngier <marc.zyngier@arm.com> 1520372677 +0000
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1521630403 +0100

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

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>