Re: [Xen-users] HVM and tap:aio?

[Sadique Puthen <sputhenp@xxxxxxxxxx>]

Omer Khalid wrote:
> Hi,
>
> I got exactly the same problem for Xen 3.1.4, HVM-enabled, 64 bit
> Host, EL4. I have tried all the combinations as hda, sda etc but it
> didn't work. Using hda does allows qemu to detect the disk though but
> it fails boot as well. 
>
> The only difference is that rather than tap:io, I am using "phy" as my
> guest is installed in LVM. The rest of the thread could be followed here:
> http://lists.xensource.com/archives/html/xen-users/2008-08/msg00786.html
>
> I am also waiting to get some insight from a Xen expert to resolve
> this problem.

As I said earlier in one other thread,  using file:/xxx/xx for hvms
doesn't have all the pitfalls  that pv guests have while using it. The
code is entirely different for storage handling with file:/ for pv and
fv. So it's safe to use file:/ for hvms while it's not for PV. Until
recently tap:aio is not supported for hvms, not sure whether this has
changed in latest versions or not.

--Sadique

>
> Thanks,
> Omer
>
> On Thu, Aug 28, 2008 at 9:27 PM, - <debaan@xxxxxxxxx
> <mailto:debaan@xxxxxxxxx>> wrote:
>
>     Hello,
>
>     I'm not able to use tap:aio disk definitions with my HVM domU's. 
>     Is this supposed to work on this version of Xen, or am I doing
>     something wrong? 
>     I've tried everything I can think of.  file: works, but not
>     tap:aio: , and I understand that file: will cause OOMkiller if
>     using NFS mounts and is deprecated.
>
>     Likewise, tap:aio: for cdrom does not allow me to boot off of
>     cdrom; file: does work fine.
>
>     Furthermore, any time I use tap:aio, the bochs bios of the hvm
>     domU shows the hard disk size as 0 MBytes.
>
>     Any disk definition that I use that has tap:aio: gives the result
>     either (if tap:aio:/xen/foo/foo.img,xvda,w):
>     Booting from Hard Disk...
>     Boot from Hard Disk failed: could not read the boot disk
>     or (if specifying tap:aio:/xen/foo/foo.img,hda,w)
>     ata0 master: QEMU HARDDISK ATA-7 Hard-Disk (0 MBytes)
>     Boot from Hard Disk failed: could not read the boot disk
>
>     Host: CentOS 5.2 x86_64, kernel 2.6.18-92.1.6.el5xen
>     Xen version: 3.1.2-92.1.6.el5
>     xen_caps: xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
>     hvm-3.0-x86_32p hvm-3.0-x86_64
>     selinux: disabled for testing
>     domU: OS doesn't appear to matter; domU OS won't start loading at all.
>
>     disk lines I've tried:
>     # disk recognized as 0/1 MB, can't install
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,ioemu:sda,w",
>     "file:/xen/iso/Win2003r2_std_32bit.iso,hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,sda,w",
>     "file:/xen/iso/Win2003r2_std_32bit.iso,hdc:cdrom,r" ]
>     #disk = [ "file:/xen/ausmsit05/ausmsit05.raw,hda,w",
>     "file:/xen/iso/Win2003r2_std_32bit.iso,hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,sda1,w",
>     ",hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,xvda,w",
>     ",hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,hda:ioemu,w",
>     ",hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,ioemu:hda,w",
>     ",hdc:cdrom,r" ]
>     #disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,ioemu:xvda,w",
>     "phy:/dev/scd0,ioemu:xvdc:cdrom,r" ]
>     # Boot from Hard Disk failed: could not read the boot disk
>     disk = [ "tap:aio:/xen/ausmsit05/ausmsit05.raw,hda,w",
>     "tap:aio:/xen/iso/win2003r2_std_32bit_disk1of2.iso,hdc:cdrom,r" ]
>
>     in the last example, this is the output of xm block-list ausmsit05
>     --long
>     (768
>         ((backend-id 0)
>             (virtual-device 768)
>             (device-type disk)
>             (state 1)
>             (backend /local/domain/0/backend/tap/55/768)
>         )
>     )
>     (5632
>         ((backend-id 0)
>             (virtual-device 5632)
>             (device-type cdrom)
>             (state 1)
>             (backend /local/domain/0/backend/tap/55/5632)
>         )
>     )
>     and this is from xend.log:
>
>     [2008-08-28 14:18:09 xend 3692] DEBUG (blkif:24) exception looking
>     up device number for hda: [Errno 2] No such file or directory:
>     '/dev/hda'
>     [2008-08-28 14:18:09 xend 3692] DEBUG (DevController:110)
>     DevController: writing {'backend-id': '0', 'virtual-device':
>     '768', 'device-type': 'disk', 'state': '1', 'backend':
>     '/local/domain/0/backend/tap/55/768'} to
>     /local/domain/55/device/vbd/768.
>     [2008-08-28 14:18:09 xend 3692] DEBUG (DevController:112)
>     DevController: writing {'domain': 'ausmsit05', 'frontend':
>     '/local/domain/55/device/vbd/768', 'format': 'raw', 'dev': 'hda',
>     'state': '1', 'params': 'aio:/xen/ausmsit05/ausmsit05.raw',
>     'mode': 'w', 'online': '1', 'frontend-id': '55', 'type': 'tap'} to
>     /local/domain/0/backend/tap/55/768.
>     [2008-08-28 14:18:09 xend 3692] DEBUG (blkif:24) exception looking
>     up device number for hdc: [Errno 2] No such file or directory:
>     '/dev/hdc'
>     [2008-08-28 14:18:09 xend 3692] DEBUG (DevController:110)
>     DevController: writing {'backend-id': '0', 'virtual-device':
>     '5632', 'device-type': 'cdrom', 'state': '1', 'backend':
>     '/local/domain/0/backend/tap/55/5632'} to
>     /local/domain/55/device/vbd/5632.
>     [2008-08-28 14:18:09 xend 3692] DEBUG (DevController:112)
>     DevController: writing {'domain': 'ausmsit05', 'frontend':
>     '/local/domain/55/device/vbd/5632', 'format': 'raw', 'dev': 'hdc',
>     'state': '1', 'params':
>     'aio:/xen/iso/win2003r2_std_32bit_disk1of2.iso', 'mode': 'r',
>     'online': '1', 'frontend-id': '55', 'type': 'tap'} to
>     /local/domain/0/backend/tap/55/5632.
>
>     Thank you in advance for any help you can offer.
>
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>
>
>
>
> -- 
> Omer
>
> -------------------------------------------------------
> CERN -- European Organization for Nuclear
> Research, IT Department, CH-1211,
> Geneva 23, Switzerland
>
> Phone: +41 (0) 22 767 2224
> Fax: +41 (0) 22 766 8683
> E-mail : Omer.Khalid@xxxxxxx
> Homepage: http://cern.ch/Omer.Khalid
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