Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver

Benjamin Herrenschmidt
2007-07-13T23:07:11Z

On Fri, 2007-07-13 at 09:02 -0400, James Bottomley wrote:
> On Wed, 2007-07-04 at 15:22 +0200, Geert Uytterhoeven wrote:
> > + kaddr = kmap_atomic(sgpnt->page, KM_USER0);
> > + if (!kaddr)
> > + return -1;
> > + len = sgpnt->length;
> > + if ((req_len + len) > buflen) {
> > + active = 0;
> > + len = buflen - req_len;
> > + }
> > + memcpy(kaddr + sgpnt->offset, buf + req_len,
> > len);
> > + kunmap_atomic(kaddr, KM_USER0);
>
> This isn't a SCSI objection, but this sequence appears several times in
> this driver. It's wrong for a non-PIPT architecture (and I believe the
> PS3 is VIPT) because you copy into the kernel alias for the page, which
> dirties the line in the cache of that alias (the user alias cache line
> was already invalidated). However, unless you flush the kernel alias to
> main memory, the user could read stale data. The way this is supposed
> to be done is to do a

Nah, we have no cache aliasing on ppc, at least not that matter here and
not on cell.

Ben.