Re: [Qemu-devel] [PATCH 1/2] dataplane: drop copy_in_vring_desc()

[Greg Kurz]

On Fri, 26 Jun 2015 12:28:45 +0200
Cornelia Huck <address@hidden> wrote:

> On Fri, 26 Jun 2015 09:32:21 +0200
> Greg Kurz <address@hidden> wrote:
> 
> > During early virtio 1.0 devel, there were several proposals about how to
> > deal with the endianness of the vring descriptor fields:
> > - convert the decriptor to host endianness in a single place, and use its
> >   fields directly in the code
> > - keep the descriptor untouched and use virtio memory helpers to access its
> >   fields with the appropriate endianness
> > 
> > It seems like both approaches got merged: commit f5a5628cf0b6 introduces
> > an extra swap that negates the one brought by commit b0e5d90ebc3e. This
> > breaks boot in SLOF (BE client) when host is ppc64le with the following
> > QEMU error:
> > 
> > Failed to map descriptor addr 0x18e2517e00000000 len 268435456
> > 
> > A solution could be to revert f5a5628cf0b6, but dropping 
> > copy_in_vring_desc()
> > is equivalent and result in a smaller patch.
> 
> I'd prefer the revert, as the resulting code is nicer IMHO.
> 

Agreed. It is good to clear the endianness noise out of the real code. :)

> But your second patch should apply regardless.
> 

Thanks for your feedback.

> > 
> > This patch allows SLOF to boot the OS.
> > 
> > Signed-off-by: Greg Kurz <address@hidden>
> > ---
> >  hw/virtio/dataplane/vring.c |   14 ++------------
> >  1 file changed, 2 insertions(+), 12 deletions(-)