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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Jan
> Beulich
> Sent: 17 June 2016 10:26
> To: Juergen Gross
> Cc: Anthony Perard; xen-devel; sstabellini@xxxxxxxxxx; qemu-
> devel@xxxxxxxxxx; kraxel@xxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH v2] xen: fix qdisk BLKIF_OP_DISCARD for
> 32/64 word size mix
> 
> >>> On 17.06.16 at 11:14, <JGross@xxxxxxxx> 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@xxxxxxxx>
> > ---
> > 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__)).
>

Yes, it's truly grotesque and such things should be blown away with extreme 
prejudice.

  Paul
 
> Jan
> 
> 
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