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

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
  • Date: Tue, 5 Feb 2008 21:01:11 +1100
  • Delivery-date: Tue, 05 Feb 2008 02:01:40 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Achni2ggR2p2caN2Szy4krhWTtOFHgARf1zQAAByYdAAALAy6gAB3hWg
  • Thread-topic: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's

> Yes, except that last_sect = 5, because it's an inclusive range.

Yes. :)

> I'm pretty sure you can DMA to/from unaligned buffers (e.g., in this
> non-2kB aligned). Certainly blkback doesn't appear to check for it, so
> presumably we found it works!

My buffers are always page aligned anyway. I have no control over the
buffer alignment that windows gives me, so I have to copy the data back
and forth. In a previous version I would check for buffer alignment
first (windows almost always gives you buffers aligned to a page
boundry), but the windows scsi controller interface is really messed
up... you are always called at a really high irq level, and the routines
for mapping buffers to pfn's are not available in that situation.


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