[Libguestfs] [virt-v2v PATCH 2/4] test-v2v-cdrom: update the CD-ROM's bus to SATA in the converted domain

[Richard W.M. Jones]

On Wed, Sep 29, 2021 at 09:07:57PM +0200, Laszlo Ersek wrote:
> On 09/27/21 10:30, Richard W.M. Jones wrote:
> > On Mon, Sep 27, 2021 at 08:34:56AM +0200, Laszlo Ersek wrote:
> >> Per commit ac39fa292c31 ("v2v: Set machine type explicitly for outputs
> >> which support it (RHBZ#1581428).", 2020-12-04), Windows 7 guests (which
> >> are "more modern" than Windows XP guests) are converted to Q35, not I440FX
> >> boards.
> >>
> >> Per related commit d0267122e348 ("v2v: -o libvirt: Map IDE disks to
> >> bus="sata" on Q35.", 2020-12-04), when a Windows 7 guest with an IDE
> >> CD-ROM -- hence, an I440FX board -- is converted, the CD-ROM in the
> >> converted domain will be on the SATA bus (Q35 does not have an IDE
> >> controller, only a SATA controller).
> >>
> >> Because the Windows guest used in "test-v2v-cdrom" is "Windows 7 Phony
> >> Edition", it triggers the above cascade, and currently fails with:
> >>
> >>> --- ./test-v2v-cdrom.expected   2021-09-03 22:51:31.026185527 +0200
> >>> +++ test-v2v-cdrom.d/disks      2021-09-19 13:01:47.471745622 +0200
> >>> @@ -4,5 +4,5 @@
> >>>      </disk>
> >>>      <disk device='cdrom' type='file'>
> >>>        <driver name='qemu' type='raw'/>
> >>> -      <target dev='hdc' bus='ide'/>
> >>> +      <target dev='sdc' bus='sata'/>
> >>>      </disk>
> >>> ./test-v2v-cdrom.sh: unexpected disk assignments
> >>
> >> The conversion seems correct, but the test expectation is stale. Most
> >> probably, commit d0267122e348 missed updating the test data. Do it now.
> > 
> > Actually the conversion is wrong - we need to update configuration
> > inside the guest.  Which is why I didn't fix this test - to remind
> > myself that there's still a bug to be fixed.
> 
> Hmm, good point; now I remember that the i440fx->q35 machine type change
> is basically a motherboard replacement for Windows.
> 
> So do we have to update some "windows device paths" (leading to the
> CD-ROM) in the registry?

We currently partially install the virtio block drivers in the Windows
guest (just enough to get the guest to boot on the target), and
Windows itself re-installs the virtio block driver and other drivers
it needs, and that's enough to get it to see C:

As for other hard disk partitions, Windows does indeed contain a
mapping to other drives in the Registry but IIRC it's not sensitive to
the device driver (unlike Linux /dev/vdX vs /dev/sdX).  If you're
interested in that, see libguestfs.git/daemon/inspect_fs_windows.ml:
get_drive_mappings.  We never bothered with attempting to handle
conversion of floppy drives or CD-ROMs for Windows.

On Linux we do better: We iterate over all the configuration files in
/etc and change device paths.  The significance of this bug is we need
to change (eg) /dev/hdc to /dev/<something>.  The difficulty is
working out where the device will appear on the target and not having
it conflict with any hard disk, something we partly control (see
virt-v2v.git/convert/target_bus_assignment.ml*)

Rich.

> Thanks,
> Laszlo
> 
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=1637857
> > 
> > Rich.
> > 
> >> Fixes: d0267122e348202f6fac4d833f7448409e7129c9
> >> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> >> ---
> >>  tests/test-v2v-cdrom.expected | 2 +-
> >>  tests/test-v2v-cdrom.xml.in   | 4 +++-
> >>  2 files changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tests/test-v2v-cdrom.expected b/tests/test-v2v-cdrom.expected
> >> index 34d2bf5961b0..17bd152d8e64 100644
> >> --- a/tests/test-v2v-cdrom.expected
> >> +++ b/tests/test-v2v-cdrom.expected
> >> @@ -4,5 +4,5 @@
> >>      </disk>
> >>      <disk device='cdrom' type='file'>
> >>        <driver name='qemu' type='raw'/>
> >> -      <target dev='hdc' bus='ide'/>
> >> +      <target dev='sdc' bus='sata'/>
> >>      </disk>
> >> diff --git a/tests/test-v2v-cdrom.xml.in b/tests/test-v2v-cdrom.xml.in
> >> index 6bad5eab1cd4..a6e1e3f514d5 100644
> >> --- a/tests/test-v2v-cdrom.xml.in
> >> +++ b/tests/test-v2v-cdrom.xml.in
> >> @@ -35,7 +35,9 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> >>        <disk type='file' device='cdrom'>
> >>          <driver name='qemu' type='raw'/>
> >>          <source file='@abs_top_builddir@/test-data/phony-guests/blank-disk.img'/>
> >> -        <!-- virt-v2v should preserve the device name and bus -->
> >> +        <!-- virt-v2v should change the bus to sata, due to Windows 7
> >> +             triggering a machine type change from i440fx to q35. Beyond that,
> >> +             virt-v2v should preserve the on-bus index. -->
> >>          <target dev='hdc' bus='ide'/>
> >>        </disk>
> >>      </devices>
> >> -- 
> >> 2.19.1.3.g30247aa5d201
> >>
> >>
> >> _______________________________________________
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> >> Libguestfs at redhat.com
> >> https://listman.redhat.com/mailman/listinfo/libguestfs
> > 

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v