Commit d3eeb1d77c5d ("xen/gntdev: use mmu_interval_notifier_insert")
missed a test for use_ptemod when calling mmu_interval_read_begin(). Fix
that.
Fixes: d3eeb1d77c5d ("xen/gntdev: use mmu_interval_notifier_insert")
CC: stable@xxxxxxxxxxxxxxx # 5.5
Reported-by: Ilpo JÃrvinen <ilpo.jarvinen@xxxxxxxxxxxxxx>
Tested-by: Ilpo JÃrvinen <ilpo.jarvinen@xxxxxxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>