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RE: [Xen-users] GPL PV TAP cow incompatible?

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] GPL PV TAP cow incompatible?
From: Martin Kjær Jørgensen <shaoh@xxxxxxx>
Date: Mon, 09 Mar 2009 12:39:56 +0100
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I've tried testing the unmoddified drivers for Linux HVM.
Apparently tap:aio works but not tap:qcow. This with a patched qemu (ioemu-qemu-xen) patched with recent qemu_disable_patches.diff.
My disk config is:

disk = [ 'tap:qcow:/xen/test.qcow,xvda,w', 'tap:qcow:/xen/test2.qcow,xvdb,w', 'tap:aio:/xen/test3.raw,xvdc,w', 'file:/root/debian-500-amd64-netinst.iso,hdc:cdrom,r' ]

On Dom0 upon xen-vbd.ko insertion dmesg shows:

[13644.995275] blktap: ring-ref 8, event-channel 6, protocol 1 (x86_64-abi)
[13644.997697] blktap: ring-ref 9, event-channel 7, protocol 1 (x86_64-abi)
[13644.999927] blktap: ring-ref 10, event[ 112.122528] xen-vbd: registered block device major 202

My DomU Linux HVM dmesg shows:
[  112.122528] xen-vbd: registered block device major 202
[  112.123653]  xvdc: unknown partition table
[  112.171299] register_blkdev: cannot get major 22 for ide
[ 112.172410] vbd vbd-5632: 19 xlvbd_add at /local/domain/0/backend/vbd/8/5632

Only the tap:aio is shown in the DomU.

/Martin

Quoting James Harper <james.harper@xxxxxxxxxxxxxxxx>:


On Mon, Mar 2, 2009 at 12:53 AM, Martin Kjær Jørgensen <shaoh@xxxxxxx>
wrote:
Could you send me a short description of your setup so that i can
compare
with my own? It sound like i'm missing some stupid setting somewhere...


In my setup tap:aio works, but tap:qcow doesn't. I guess it's a bug.


When debugging this a while ago I found that tap:* wasn't passing through the sector count correct. I have since upgraded to 3.3.1 and tap:aio works fine. I haven't tested tap:qcow.

Have you tried with a Linux HVM domain with PV drivers?

James





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