77913bbcb4
Even though we've zeroed the PDE, the GPU may have cached the PD, so we need to flush when deleting them. Noticed while working on replacement MMU code, but a backport might be a good idea, so let's fix it in the current code too. Signed-off-by: Ben Skeggs <bskeggs@redhat.com> Cc: stable@vger.kernel.org