Messages in this thread | | | Date | Mon, 2 May 2022 15:31:41 +0200 | Subject | Re: [PATCH v2 08/19] xen/shbuf: switch xen-front-pgdir-shbuf to use INVALID_GRANT_REF | From | Juergen Gross <> |
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On 29.04.22 17:28, Oleksandr wrote: > > Hello Juergen > > > On 28.04.22 21:03, 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... >> 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. > > > In addition to what I said yesterday: > > PV Display also uses this xen-front-pgdir-shbuf framework. It's protocol > (displif.h) also mentions the same as sndif.h if the context of gref_dir_next_page: > > * gref_dir_next_page - grant_ref_t, reference to the next page describing > * page directory. Must be 0 if there are no more pages in the list. > > > With that local change both PV devices work in my environment. > > diff --git a/drivers/xen/xen-front-pgdir-shbuf.c > b/drivers/xen/xen-front-pgdir-shbuf.c > index fa2921d..ad4a88e 100644 > --- a/drivers/xen/xen-front-pgdir-shbuf.c > +++ b/drivers/xen/xen-front-pgdir-shbuf.c > @@ -346,7 +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 = INVALID_GRANT_REF; > + page_dir->gref_dir_next_page = 0; > } > > /** > @@ -375,7 +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 = INVALID_GRANT_REF; > + page_dir->gref_dir_next_page = 0; > } else { > to_copy = XEN_NUM_GREFS_PER_PAGE; > page_dir->gref_dir_next_page = buf->grefs[i + 1];
I think I'll introduce a proper define for that purpose.
Juergen [unhandled content-type:application/pgp-keys][unhandled content-type:application/pgp-signature] | |