Re: [PATCH][XEN] PV blk backend: Make 32bit PV guests work on 64bit PV Dom0

[Christoph Egger <Christoph.Egger@amd.com>]

On Monday 28 July 2008 14:23:00 Keir Fraser wrote:
> Just do the same as we do in Linux and put these defs in your NetBSD
> private header space.

That sounds like "All OS's have to go the Linux way" (which also includes
Xen's Minios (stubdom))  instead of "fix it once and for all".

Christoph

>
>  -- Keir
>
> On 28/7/08 12:46, "Christoph Egger" <Christoph.Egger@amd.com> wrote:
> > Hi,
> >
> > Attached patch makes the PV block driver for 32bit PV guests working on
> > 64bit PV Dom0.
> >
> > In the io/blkif.h,  the 'id' field of
> > struct blkif_request is 64bit, but on a LP32 system it's aligned on
> > 32bits, while it'll be aligned to 64bits on a LP64 system. So on LP64
> > there'll be 4 bytes of padding between handle and id. The same is true
> > for struct blkif_response: it's 11 bytes long, so will be aligned
> > differently in the ring between a 32 and 64bit systems.
> >
> > In order to fix this, attached patch introduces in the public headers,
> > blkif_request/blkif_response, blkif_x86_32_request/blkif_x86_32_response
> > and blkif_x86_64_request/blkif_x86_64_response.
> > NetBSD is doing so io/blkif.h in the public headers, while Linux
> > does so in include/xen/blkif.h in the linux sources. But the result is
> > the same ...
> >
> > Successfully tested with the combinations:
> >
> > 64bit Dom0                32bit PAE PV guest
> > NetBSD                       Linux
> > Linux                            NetBSD
> >
> > The combinations 64bit Dom0, 64bit PV DomU works with and without this
> > patch.
> >
> > Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>



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