[Xen-devel] Re: [RFC PATCH v01] Xen PVSCSI drivers for pvops xen/stable-2.6.32.x kernel

[Nathanael Rensen <nathanael@xxxxxxxxxxxxxxxx>]

On 7 January 2011 06:35,  Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> Hello,
>
> http://pasik.reaktio.net/xen/patches/xen-pvscsi-drivers-linux-2.6.32.27-pvops-v01.diff
>
> This is the first version of Xen PVSCSI drivers, both the scsiback backend and
> scsifront frontend, ported from Novell SLES11SP1 2.6.32 Xenlinux kernel to
> pvops xen/stable-2.6.32.x branch.
>
> -- Pasi

That's great. Some comments based on my experience with pvusb:

1) You've added GNTST_eagain into include/xen/interface/grant_table.h.
When porting the pvusb drivers I removed the "check and retry" loops
based on GNTST_eagain because I noticed that netback and blkback don't
do that. Looking at the grant_table code in xen-4.0-testing I don't
think GNTST_eagain is used now. Perhaps someone with knowledge of the
history of GNTST_eagain could help to clarify.

2) When porting pvusb I found I had to take care with the
gnttab_grant_foreign_access_ref calls. Following the example of
blkback I replaced
   buffer_pfn = page_to_phys(page) >> PAGE_SHIFT;
with
   buffer_mfn = pfn_to_mfn(page_to_pfn(page));
The situation for pvscsi looks a bit more involved (e.g. buffer_pfn++).

3) The existing xen-netfront, xen-blkfront and xen-pcifront have been
converted to a single .c module when ported to pvops. I followed that
lead with pvusb. You might like to do the same for consistency.

Nathanael

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