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Bug 2044911 - virt-p2v conversion hangs with RHEL9 virt-v2v
Summary: virt-p2v conversion hangs with RHEL9 virt-v2v
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 9
Classification: Red Hat
Component: virt-v2v
Version: 9.0
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: ---
Assignee: Virtualization Maintenance
QA Contact: tingting zheng
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2022-01-25 10:46 UTC by tingting zheng
Modified: 2022-05-17 13:43 UTC (History)
8 users (show)

Fixed In Version: virt-v2v-1.45.97-3.el9
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2022-05-17 13:42:09 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Issue Tracker RHELPLAN-109553 0 None None None 2022-01-25 10:50:45 UTC
Red Hat Product Errata RHEA-2022:2566 0 None None None 2022-05-17 13:42:19 UTC

Description tingting zheng 2022-01-25 10:46:58 UTC 
Description of problem:
RHEL 7 virt-p2v conversion hangs with RHEL9 virt-v2v.

Version-Release number of selected component (if applicable):
Virt-p2v-1.40.2-1.el7.iso
libvirt-8.0.0-1.el9.x86_64
libguestfs-1.46.1-2.el9.x86_64
qemu-kvm-6.2.0-4.el9.x86_64
virt-v2v-1.45.97-2.el9.x86_64
virtio-win-1.9.19-5.el9_b.noarch
nbdkit-1.28.4-2.el9.x86_64
libnbd-1.10.3-1.el9.x86_64


How reproducible:
100%

Steps to Reproduce:
1.Launch RHEL7 virt-p2v client, connect to RHEL9 server.
2.Use virt-p2v to convert.

Actual results:
The conversion hangs after coping disk.

Expected results:
The conversion can be finished successfully.

Additional info:
logs:http://fileshare.englab.nay.redhat.com/pub/section3/libvirtmanual/tzheng/virt-p2v-20220124-6e0cxsb6/
Comment 1 tingting zheng 2022-01-25 10:49:26 UTC 
Comments from Richard.
Looking at the log and referring to:

https://libguestfs.org/virt-p2v.1.html#how-virt-p2v-works

we can see that port 34337 is set up as the ssh reverse forwarding
port (ie. on localhost from the point of view of virt-v2v, connected
to qemu-nbd on the virt-p2v host).

We successfully set up nbdkit-nbd-plugin to forward in0 to this port.
(This is different from how old virt-v2v worked - it would have
created a qcow2 file backed by nbd:localhost:34337).

Everything seems to go fine during conversion.

However when we start copying we make several connections to in0 and I
suspect what is happening is that nbdkit-nbd-plugin makes several
connections to qemu-nbd.  However qemu-nbd only permits a single
connection by default and so the extra connections will deadlock.

We cannot change virt-p2v (because RHEL 7), but we can patch virt-v2v.
In this case nbdkit-nbd-plugin has a shared=true option which makes it
share a single connection to the proxied nbd server (ie. qemu-nbd).

So my guess is that the following patch will fix it:

diff --git a/input/input_libvirt.ml b/input/input_libvirt.ml
index 33f61086ec..42050c157b 100644
--- a/input/input_libvirt.ml
+++ b/input/input_libvirt.ml
@@ -76,6 +76,7 @@ and libvirt_servers dir disks =
          Nbdkit.add_filter cmd "cow";
          Nbdkit.add_arg cmd "hostname" hostname;
          Nbdkit.add_arg cmd "port" (string_of_int port);
+         Nbdkit.add_arg cmd "shared" "true";
          let _, pid = Nbdkit.run_unix ~socket cmd in

          (* --exit-with-parent should ensure nbdkit is cleaned
Comment 2 Richard W.M. Jones 2022-01-25 11:28:04 UTC 
Patch posted:
https://listman.redhat.com/archives/libguestfs/2022-January/msg00167.html
Comment 3 Richard W.M. Jones 2022-01-25 11:31:52 UTC 
Tingting tested this and confirmed the fix works.
Comment 4 tingting zheng 2022-01-25 12:29:24 UTC 
Tested the build and set Verified:Tested for this bug.
Comment 5 Richard W.M. Jones 2022-01-26 13:00:57 UTC 
Fixed upstream in:
https://github.com/libguestfs/virt-v2v/commit/20019b5cadc1434ac09842e2045a7d5635561835
Comment 8 tingting zheng 2022-01-27 07:20:08 UTC 
Tested the bug with:
Virt-p2v-1.40.2-1.el7.iso
libguestfs-1.46.1-2.el9.x86_64
virt-v2v-1.45.97-3.el9.x86_64
nbdkit-1.28.5-1.el9.x86_64
libvirt-8.0.0-2.el9.x86_64
qemu-kvm-6.2.0-5.el9.x86_64

1.Launch RHEL7 virt-p2v client, connect to RHEL9 server.
2.Use virt-p2v to start conversion to local kvm and RHV, the conversion can be finished successfully.

Refer to the above comments, move the bug to VERIFIED.
Comment 10 errata-xmlrpc 2022-05-17 13:42:09 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (new packages: virt-v2v), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2022:2566
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