[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Serge Hallyn]

I see, misunderstood.

Reproduced with latest git://git.qemu.org/qemu.git as well, so marked as
affecting upstream QEMU project.

** Also affects: qemu
   Importance: Undecided
       Status: New

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Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  New
Status in “qemu” package in Ubuntu:
  Confirmed

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

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[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Paolo Bonzini]

There's no such thing as a virtio-blk CD-ROM, only hard-disks. For
installation it shouldn't matter, since .iso images usually can work
also as hard-disk images (for putting them on a USB stick).

If you want to test installation from a "real" virtio CD-ROM, use
virtio-scsi:

-drive file=/path/to/file.iso,if=none,id=cd -device virtio-scsi-pci
-device scsi-cd,drive=cd

or

-drive file=/path/to/file.iso,if=none,media=cdrom,id=cd -device virtio-
scsi-pci -device scsi-disk,drive=cd


** Changed in: qemu
       Status: New => Invalid

** Changed in: qemu (Ubuntu)
       Status: Confirmed => Invalid

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Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

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[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Phillip Susi]

It seems the installer does not consider virtio devices when doing its
search.  It also seems the installer does not have the virtio-scsi
module, and it seems a bit wasteful to go through a layer of scsi
emulation.

Shouldn't qemu at least warn you that the media=argument does nothing on
virtio devices instead of silently ignoring it?  Or better yet,
shouldn't it automatically use virtio-scsi instead?

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https://bugs.launchpad.net/bugs/1155403

Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

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[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Laszlo Ersek]

Consider filing a Debian/Ubuntu bug so that their initramfs / installer
/ live disk comes with virtio-scsi. See eg.
https://bugzilla.redhat.com/show_bug.cgi?id=864012

** Bug watch added: Red Hat Bugzilla #864012
   https://bugzilla.redhat.com/show_bug.cgi?id=864012

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https://bugs.launchpad.net/bugs/1155403

Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
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[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Paolo Bonzini]

> It seems the installer does not consider virtio devices when doing its
search.

That's another bug in the installer then.

> it seems a bit wasteful to go through a layer of scsi emulation.

Indeed treating the virtio disk similarly to installation from a USB
stick is better, but SCSI emulation is actually a very good way to not
reinvent the wheel. CD-ROM/DVD-ROM media need a lot of magic (such as
subdivision of the medium into tracks, different media formats, etc.)
and emulating those in virtio-blk would be even more wasteful.

> Shouldn't qemu at least warn you that the media=argument does nothing
> on virtio devices instead of silently ignoring it?

Yes, that's a legitimate request.

>  Or better yet, shouldn't it automatically use virtio-scsi instead?

No, virtio-scsi is relatively new and not all distros have picked it up
yet.

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Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1155403/+subscriptions

Re: [Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Markus Armbruster]

Phillip Susi <psusi@ubuntu.com> writes:

> It seems the installer does not consider virtio devices when doing its
> search.  It also seems the installer does not have the virtio-scsi
> module, and it seems a bit wasteful to go through a layer of scsi
> emulation.

virtio-scsi performs just fine.

> Shouldn't qemu at least warn you that the media=argument does nothing on
> virtio devices instead of silently ignoring it?  Or better yet,
> shouldn't it automatically use virtio-scsi instead?

Incompatible changes.  Doesn't mean we can't make them ever, only we
better be careful.

If we make incompatible changes to if=virtio, we might be better off
going all the way and switching it over to virtio-scsi wholesale.

Re: [Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Phillip Susi]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 3/18/2013 5:13 AM, Paolo Bonzini wrote:
>> Or better yet, shouldn't it automatically use virtio-scsi
>> instead?
> 
> No, virtio-scsi is relatively new and not all distros have picked
> it up yet.

And not all distros ship hybrid cd images that their installers are
happy with on virtio.  Given that either one may or may not work, I
think it best to honor the user's request and emulate the cd.


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-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1155403

Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1155403/+subscriptions

[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Paolo Bonzini]

if=virtio means virtio-blk, not virtio-something.

Also, Linux is perfectly fine with ISO images on virtio, the Ubuntu
installer is  wrong in not scanning virtio disks. Since Ubuntu wouldn't
work either way, they should first fix the installer and then we can re-
evaluate if QEMU can do something (probably not, except warning for
media=cdrom).

** Also affects: debian-installer (Ubuntu)
   Importance: Undecided
       Status: New

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1155403

Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “debian-installer” package in Ubuntu:
  New
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1155403/+subscriptions

Re: [Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Phillip Susi]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 3/18/2013 11:17 AM, Paolo Bonzini wrote:
> if=virtio means virtio-blk, not virtio-something.

Why do you say that?  I would say that virtio means use
paravirtualized IO rather than emulating some real hardware.  Whether
that ends up being done with virtio-blk, or virtio-scsi is an
implementation detail.  The media argument seems a perfectly natural
way to select between the two.


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You received this bug notification because you are a member of qemu-
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Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “debian-installer” package in Ubuntu:
  New
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1155403/+subscriptions

[Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Paolo Bonzini]

> The media argument seems a perfectly natural
> way to select between the two.

Then how do you distinguish between a virtio-scsi and a virtio-blk hard
disk?  These may even require changes to the guest, since one becomes
/dev/vda and the other becomes /dev/sda.

virtio-scsi will grow more and more functionality, while virtio-blk will
likely remain a secondary choice for performance or backwards-
compatibility.

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https://bugs.launchpad.net/bugs/1155403

Title:
  virtio cdrom detected as hard disk

Status in QEMU:
  Invalid
Status in “debian-installer” package in Ubuntu:
  New
Status in “qemu” package in Ubuntu:
  Invalid

Bug description:
  Trying to install Ubuntu or Debian using virtio to emulate the cdrom
  fails.  This appears to be due to the drive appearing to be a hard
  disk, rather than a cdrom, despite the media=cdrom argument to qemu.

  I'm not sure if this is a bug in qemu, or the kernel virtio driver?

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1155403/+subscriptions

Re: [Qemu-devel] [Bug 1155403] Re: virtio cdrom detected as hard disk

[Markus Armbruster]

Phillip Susi <psusi@ubuntu.com> writes:

> On 3/18/2013 11:17 AM, Paolo Bonzini wrote:
>> if=virtio means virtio-blk, not virtio-something.
>
> Why do you say that?  I would say that virtio means use
> paravirtualized IO rather than emulating some real hardware.  Whether
> that ends up being done with virtio-blk, or virtio-scsi is an
> implementation detail.

Not really, because the "detail" requires different drivers in the
guest.

>                         The media argument seems a perfectly natural
> way to select between the two.

"Perfectly natural"?  Me thinks you're overstating your case.  Having
"media=cdrom" select virtio-scsi over virtio-blk is at best a hack.
virtio-scsi vs. virtio-blk is *not* about disk vs. CD-ROM.  It's about
two different mass storage controllers, one of whom happens not to
support CD-ROMs today.