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

To: Nathanael Rensen <nathanael@xxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [RFC PATCH v01] Xen PVSCSI drivers for pvops xen/stable-2.6.32.x kernel
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Fri, 7 Jan 2011 12:35:20 +0200
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Ian Campbell <Ian.Campbell@xxxxxxxxxx>
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On Fri, Jan 07, 2011 at 06:03:59PM +0800, Nathanael Rensen wrote:
> On 7 January 2011 06:35,  Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> > Hello,
> >
> > http://pasik.reaktio.net/xen/patches/xen-pvscsi-drivers-linux-
> >
> > 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.

Yep, I commented about this on the other email.

> 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++).

Yeah, I had to hack that stuff aswell.. I was pretty tired so not sure
at all I did it correctly :)

I'll get back to it some day now and take another look at it.
And actually do some *testing* with the patch :)

> 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.

Yep, I noticed this aswell. The first version was meant to be
"minimal changes just to make it compile". I need to do this change aswell.

Thanks for the comments! 

-- Pasi

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