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Re: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's

  • To: James Harper <james.harper@xxxxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
  • Date: Tue, 05 Feb 2008 08:30:43 +0000
  • Delivery-date: Tue, 05 Feb 2008 00:31:19 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Achni2ggR2p2caN2Szy4krhWTtOFHgARf1zQ
  • Thread-topic: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's

On 5/2/08 00:09, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

> It looks like mounting a physical CDROM under the windows gpl pv drivers
> doesn't work, and I suspect that the problem is because the CDROM uses a
> sector size of 2048 instead of 512.
> Do the pages passed between the front and backend scale to using
> different sector sizes, or do I have to do some magic to fudge them back
> to 512?

The 'sectors' referenced in blkif requests are always 512 bytes. So if you
read 'sector-size' of 2048 from xenstore during blkif setup, that means that
the #sector alignments and sizes you send in requests must be multiples of

 -- Keir

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