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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> |
|---|---|
| Subject: | Re: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's |
| From: | Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> |
| Date: | Tue, 05 Feb 2008 09:03:13 +0000 |
| Delivery-date: | Tue, 05 Feb 2008 01:03:12 -0800 |
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| Thread-topic: | [Xen-devel] blkfront/back and sector size of 2048 with CDROM's |
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On 5/2/08 08:52, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote: > Okay... a forinstance... > > I give windows a sector size of 2048 based on what I have read from > xenstore. Windows isssues a read request for sector 1 (byte offset > 2048), and a length of 1 sector. > > My read buffer is aligned at 1024 bytes into the page, so in the blkif > request I set nr_segments = 1, sector_number = 4 (1 * (2048 / 512)), and > in the first (and only) segment, first_sect = 2 and last_sect = 6. > > Does that sound right? Yes, except that last_sect = 5, because it's an inclusive range. I'm pretty sure you can DMA to/from unaligned buffers (e.g., in this case non-2kB aligned). Certainly blkback doesn't appear to check for it, so presumably we found it works! -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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