On Mon, 16 May 2022 09:22:09 +0200
Nico Boehr <nrb@xxxxxxxxxxxxx> wrote:
> On Thu, 2022-04-14 at 10:02 +0200, Claudio Imbrenda wrote:
>
> [...]
> > +/**
> > + * s390_replace_asce - Try to replace the current ASCE of a gmap
> > with
> > + * another equivalent one.
> > + * @gmap the gmap
> > + *
> > + * If the allocation of the new top level page table fails, the ASCE
> > is not
> > + * replaced.
> > + * In any case, the old ASCE is always removed from the list.
> > Therefore the
> > + * caller has to make sure to save a pointer to it beforehands,
> > unless an
> > + * intentional leak is intended.
> > + */
> > +int s390_replace_asce(struct gmap *gmap)
> > +{
> >
> [...]
> > + /* Set new table origin while preserving existing ASCE
> > control bits */
> > + asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
> > + WRITE_ONCE(gmap->asce, asce);
>
> Can someone concurrently touch the control bits?
should not happen, nobody is using the ASCE while we replace it
moreover, all callers of s390_replace_asce hold kvm->lock, as do all
functions changing the ASCE
