From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex Bligh <alex@alex.org.uk>
Subject: Re: Fatal crash on xen4.2 HVM + qemu-xen dm + NFS
Date: Tue, 22 Jan 2013 13:02:23 +0000
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Reply-To: Alex Bligh <alex@alex.org.uk>
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To: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Konrad Wilk <konrad.wilk@oracle.com>, Xen Devel <xen-devel@lists.xen.org>, Alex Bligh <alex@alex.org.uk>, Jan Beulich <JBeulich@suse.com>, Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>
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Ian,

--On 22 January 2013 10:05:16 +0000 Ian Campbell <Ian.Campbell@citrix.com> 
wrote:

> I've never looked inside xen_qdisk so I can't really advise, but that
> sound broadly correct, except you'd want to use gnttab_copy not mmap
> +memcpy. e.g. (totally making up the API because I'm too lazy to go
> look):
> 	buffer = malloc(SIZE)
> 	if (writing)
> 		gnttab_copy_from(buffer, gntref, size)
>
> 	io->buffer = buffer
> 	submit(io)
> ... wait for completion:
> 	if (reading)
> 		gnttab_copy_to(...)
> 	free(io->buffer)
>
> Hopefully you get the idea ;-) Sounds like before the ... goes in
> ioreq_map and after the ... goes in ioreq_unmap.

Thanks. If the O_DIRECT thing doesn't fix it, I'll take a look again.
My initial analysis was that a copy interface wasn't available through
xc_ type functions.

-- 
Alex Bligh