RE: [Xen-devel] HVM domain with write caching going on somewheretodisk

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

More testing... there is one write done by windows via the BIOS
interface on boot, and that is to sector 2958215 on my system. By using
dd, I only finally see the results of that write after I have flushed
out the page cache by doing a few big file transfers. That is even after
I got O_DIRECT working...

Something strange is going on I think.

James

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of James Harper
> Sent: Friday, 9 November 2007 12:17
> To: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] HVM domain with write caching going on
> somewheretodisk
> 
> >
> > I just changed the open in block.c to include O_DIRECT, but it fails
> to
> > boot. The VNC session flashes up very quickly and I can definitely
see
> > the BIOS there but nothing else.
> >
> > I'll have a look a bit further tomorrow...
> >
> 
> The reason it was failing was that O_DIRECT requires the buffer to the
> read() and write() function to be page aligned. I have put some bounce
> buffer code into raw_read() and raw_write() in block.c, which does
this
> (very inefficiently of course), and still get the same error, so maybe
> this isn't the problem after all...
> 
> Any other suggestions?
> 
> Thanks
> 
> James
> 
> 
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