Re: [Qemu-devel] [Xen-devel] [PATCH v2] xen: fix qdisk BLKIF_OP_DISCARD for 32/64 word size mix

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
> Juergen Gross
> Sent: 17 June 2016 10:31
> To: Jan Beulich
> Cc: Anthony Perard; xen-devel; sstabellini@kernel.org; qemu-
> devel@nongnu.org; kraxel@redhat.com
> Subject: Re: [Xen-devel] [PATCH v2] xen: fix qdisk BLKIF_OP_DISCARD for
> 32/64 word size mix
> 
> On 17/06/16 11:26, Jan Beulich wrote:
> >>>> On 17.06.16 at 11:14, <JGross@suse.com> wrote:
> >> In case the word size of the domU and qemu running the qdisk backend
> >> differ BLKIF_OP_DISCARD will not work reliably, as the request
> >> structure in the ring have different layouts for different word size.
> >>
> >> Correct this by copying the request structure in case of different
> >> word size element by element in the BLKIF_OP_DISCARD case, too.
> >>
> >> The easiest way to achieve this is to resync hw/block/xen_blkif.h with
> >> its original source from the Linux kernel.
> >>
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> >> ---
> >> V2: resync with Linux kernel version of hw/block/xen_blkif.h as
> >>     suggested by Paul Durrant
> >
> > Oh, I didn't realize he suggested syncing with the Linux variant.
> > Why not with the canonical one? I have to admit that I particularly
> > dislike Linux'es strange union-izng, mainly because of it requiring
> > this myriad of __attribute__((__packed__)).
> 
> What would be gained by syncing with the canonical one? The part to be
> modified is available in the Linux variant only.
>

So there's something in the Linux variant that's not in the canonical header?! Well that needs to be fixed first and then, yes, I did mean re-sync with the canonical header.

  Paul
 
> 
> Juergen
> 
> 
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