On Mon, Nov 04, 2019 at 03:31:53PM -0500, Jerome Glisse wrote:
> > Note for Jason: the (a) or (b) items are talking about the vfio case, which is
> > one of the two call sites that now use pin_longterm_pages_remote(), and the
> > other one is infiniband:
> >
> > drivers/infiniband/core/umem_odp.c:646: npages = pin_longterm_pages_remote(owning_process, owning_mm,
> > drivers/vfio/vfio_iommu_type1.c:353: ret = pin_longterm_pages_remote(NULL, mm, vaddr, 1,
>
> vfio should be reverted until it can be properly implemented.
> The issue is that when you fix the implementation you might
> break vfio existing user and thus regress the kernel from user
> point of view. So i rather have the change to vfio reverted,
> i believe it was not well understood when it got upstream,
> between in my 5.4 tree it is still gup_remote not longterm.
It is clearly a bug, vfio must use LONGTERM, and does right above this
remote call:
if (mm == current->mm) {
ret = get_user_pages(vaddr, 1, flags | FOLL_LONGTERM, page,
vmas);
} else {
ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page,
vmas, NULL);
I'm not even sure that it really makes any sense to build a 'if' like
that, surely just always call remote??
Jason
