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Re: [PATCH v4] acpi: pcihp: allow repeating hot-unplug requests
From: |
Kashyap Chamarthy |
Subject: |
Re: [PATCH v4] acpi: pcihp: allow repeating hot-unplug requests |
Date: |
Thu, 4 May 2023 16:33:11 +0200 |
On Wed, Apr 26, 2023 at 07:20:08PM +0200, Kashyap Chamarthy wrote:
> On Wed, Apr 26, 2023 at 07:40:02PM +0300, Michael Tokarev wrote:
> > 18.04.2023 12:04, Igor Mammedov wrote:
> > > with Q35 using ACPI PCI hotplug by default, user's request to unplug
> > > device is ignored when it's issued before guest OS has been booted.
> > > And any additional attempt to request device hot-unplug afterwards
> > > results in following error:
> > >
> > > "Device XYZ is already in the process of unplug"
> > >
> > > arguably it can be considered as a regression introduced by [2],
> > > before which it was possible to issue unplug request multiple
> > > times.
> >
> > Stable-8.0 material?
>
> FWIW, I'd say, yes. This fix is useful for stable releases. As this
> solves a real problem for upper-management tools.
>
> I have tested this fix; and it works. I'll post my testing notes /
> reproducer in a follow-up email. In short, I followed the
> reproducer steps from here[1].
Tested-by: Kashyap Chamarthy <kchamart@redhat.com>
It solves the device-detach bug noted here[1]. As promised, here are my
reproducer notes (expanded from[1]):
Disk image prep
---------------
(1) Download an Ubuntu "Jammy" guest image from here:
https://cloud-images.ubuntu.com/jammy/current/jammy-server-cloudimg-amd64.img
(2) Update the above disk image's kernel command-line to have the
guest-boot slowed down by 100 seconds; use "boot_delay=100".
(3) Have an additional image ("disk2.img") ready for hot-plug/un-plug.
Test
----
(1) Build QEMU with the patch in question:
$ git describe
7.2.94v8.0.0-rc4-1-gfa6650df6d7
(2) Use the above QEMU binary to launch the Ubuntu "Jammy" guest:
$ virsh dumpxml jammy1 | grep emulator
<emulator>/home/kashyapc/tinker-space/qemu-upstream/build/qemu-system-x86_64</emulator>
(3) Have a split `tmux` ready; start the guest in the first pane, with
the serial console logs rolling:
$ virsh start jammy1 --console
(4) Wait until the guest consoles messages start rolling. Once they do,
on the other `tmux` pane, issue the below command (it's a live
attach, followed by a detach):
$ virsh attach-disk jammy1 ./disk2.img vdb --live --persistent \
&& sleep 1 \
&& virsh detach-disk jammy1 --live ./disk2.img
Disk attached successfully
Disk detached successfully
(5) Enumerate the attached block devices to the guest. We still see the
second disk, "disk2.img":
$> virsh domblklist jammy1
Target Source
-------------------------------------------
vda /data/images/jammy-ubuntu.qcow2
vdb /data/images/disk2.img
(6) Now detach the disk from the inactive guest XML (that affects
next boot) by using "--persistent" flag; and enumerate the live
block devices (we still see the second disk)
$> virsh detach-disk jammy1 --persistent /data/images/disk2.img
Disk detached successfully
$> virsh domblklist jammy1
Target Source
-------------------------------------------
vda /data/images/jammy-ubuntu.qcow2
vdb /data/images/disk2.img
(NOTE: We're using two separate calls to `virsh detach-disk`, one with
"--live" and the other with "--persistent" based on upstream libvirt
recommendation in [1].)
(7) Again, re-issue the detach command with just "--live" flag:
$> virsh detach-disk jammy1 --live /data/images/disk2.img
Disk detached successfully
(8) Re-enumerate the attached block devices:
$> virsh domblklist jammy1
Target Source
-------------------------------------------
vda /data/images/jammy-ubuntu.qcow2
Now we see the second device is detached "for real". Overall, we were
able to successfully re-issue `device detach` while the guest is still
booting, and see through the actual detach to its logical conclusion.
[1] https://gitlab.com/libvirt/libvirt/-/issues/309 -- Disk detach is
unsuccessfull while the guest is still booting
--
/kashyap
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