This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


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

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, "xen-devel" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Tue, 5 Feb 2008 19:52:32 +1100
Delivery-date: Tue, 05 Feb 2008 00:53:02 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <C3CDCF33.134A5%Keir.Fraser@xxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <AEC6C66638C05B468B556EA548C1A77D0131AAA1@trantor> <C3CDCF33.134A5%Keir.Fraser@xxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Achni2ggR2p2caN2Szy4krhWTtOFHgARf1zQAAByYdA=
Thread-topic: [Xen-devel] blkfront/back and sector size of 2048 with CDROM's
> The 'sectors' referenced in blkif requests are always 512 bytes. So if
> read 'sector-size' of 2048 from xenstore during blkif setup, that
> that
> the #sector alignments and sizes you send in requests must be
multiples of
> 4.

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?



Xen-devel mailing list