Messages in this thread | | | Date | Mon, 2 May 2022 15:28:17 +0200 | Subject | Re: [PATCH v2 08/19] xen/shbuf: switch xen-front-pgdir-shbuf to use INVALID_GRANT_REF | From | Juergen Gross <> |
| |
On 28.04.22 20:03, Oleksandr Tyshchenko wrote: > > > On Thu, Apr 28, 2022 at 11:28 AM Juergen Gross <jgross@suse.com > <mailto:jgross@suse.com>> wrote: > > Hello Juergen > > [sorry for the possible format issue] > > Instead of using a private macro for an invalid grant reference use > the common one. > > Signed-off-by: Juergen Gross <jgross@suse.com <mailto:jgross@suse.com>> > --- > drivers/xen/xen-front-pgdir-shbuf.c | 17 ++++------------- > 1 file changed, 4 insertions(+), 13 deletions(-) > > diff --git a/drivers/xen/xen-front-pgdir-shbuf.c > b/drivers/xen/xen-front-pgdir-shbuf.c > index a959dee21134..fa2921d4fbfc 100644 > --- a/drivers/xen/xen-front-pgdir-shbuf.c > +++ b/drivers/xen/xen-front-pgdir-shbuf.c > @@ -21,15 +21,6 @@ > > #include <xen/xen-front-pgdir-shbuf.h> > > -#ifndef GRANT_INVALID_REF > -/* > - * FIXME: usage of grant reference 0 as invalid grant reference: > - * grant reference 0 is valid, but never exposed to a PV driver, > - * because of the fact it is already in use/reserved by the PV console. > - */ > -#define GRANT_INVALID_REF 0 > -#endif > - > /** > * This structure represents the structure of a shared page > * that contains grant references to the pages of the shared > @@ -83,7 +74,7 @@ grant_ref_t > xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf) > { > if (!buf->grefs) > - return GRANT_INVALID_REF; > + return INVALID_GRANT_REF; > > return buf->grefs[0]; > } > @@ -142,7 +133,7 @@ void xen_front_pgdir_shbuf_free(struct > xen_front_pgdir_shbuf *buf) > int i; > > for (i = 0; i < buf->num_grefs; i++) > - if (buf->grefs[i] != GRANT_INVALID_REF) > + if (buf->grefs[i] != INVALID_GRANT_REF) > gnttab_end_foreign_access(buf->grefs[i], 0UL); > } > kfree(buf->grefs); > @@ -355,7 +346,7 @@ static void backend_fill_page_dir(struct > xen_front_pgdir_shbuf *buf) > } > /* Last page must say there is no more pages. */ > page_dir = (struct xen_page_directory *)ptr; > - page_dir->gref_dir_next_page = GRANT_INVALID_REF; > + page_dir->gref_dir_next_page = INVALID_GRANT_REF; > } > > /** > @@ -384,7 +375,7 @@ static void guest_fill_page_dir(struct > xen_front_pgdir_shbuf *buf) > > if (grefs_left <= XEN_NUM_GREFS_PER_PAGE) { > to_copy = grefs_left; > - page_dir->gref_dir_next_page = GRANT_INVALID_REF; > + page_dir->gref_dir_next_page = INVALID_GRANT_REF; > > > I faced an issue with testing PV Sound with the current series. > > root@salvator-x-h3-4x2g-xt-domu:~# aplay /media/MoodyLoop.wav > Playing WAVE '/media/MoodyLoop.wav' : Signed 16 bit Little Endian, Rate 44100 > Hz, Stereo > (XEN) common/grant_table.c:1053:d1v2 Bad ref 0xffffffff for d6 > > Here we have an interesting situation. PV Sound frontend uses this > xen-front-pgdir-shbuf framework. Technically, this patch changes > page_dir->gref_dir_next_page (reference to the next page describing page > directory) from 0 to 0xffffffff here. > #define INVALID_GRANT_REF ((grant_ref_t)-1) > > But according to the protocol (sndif.h), "0" means that there are no more pages > in the list and the user space backend expects only that value. So > receiving 0xffffffff it assumes there are pages in the list and trying to > process...
Hmm, that's unfortunate.
> https://elixir.bootlin.com/linux/v5.18-rc4/source/include/xen/interface/io/sndif.h#L650 > <https://elixir.bootlin.com/linux/v5.18-rc4/source/include/xen/interface/io/sndif.h#L650> > > > I think, the same is relevant to backend_fill_page_dir() as well.
Thanks for finding this.
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |