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

From: James Bottomley <[email-masked]>
Date: Fri, 13 Jul 2007 09:02:21 -0400

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 

flush_kernel_dcache_page(kaddr)

before doing the kunmap.

Otherwise it looks OK from the SCSI point of view.

James