From: Thomas Lamprecht <t.lamprecht@proxmox.com>
To: "DERUMIER, Alexandre" <Alexandre.DERUMIER@groupe-cyllene.com>,
"pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>,
"aderumier@odiso.com" <aderumier@odiso.com>
Subject: Re: [pve-devel] [PATCH V2 qemu-server 1/2] enable balloon free-page-reporting
Date: Thu, 17 Mar 2022 09:35:02 +0100 [thread overview]
Message-ID: <5803a37d-7308-1e0d-89f7-fc80c9b297d8@proxmox.com> (raw)
In-Reply-To: <07ccbada79379fd6677c61d495995eed957b34af.camel@groupe-cyllene.com>
On 16.03.22 20:32, DERUMIER, Alexandre wrote:
> From my tests:
> a already booted vm without the balloon freepage option enabled --->
> migrating to new vm with balloon freepage option enabled : works
>
> Then failback it to previous node : works
>
>
> But starting a new vm with the option enabled then migrate it to a new
> vm withtout the option:
>
> migration die on resume.
>
> 2022-03-16 20:28:30 average migration speed: 1.5 GiB/s - downtime 30 ms
> 2022-03-16 20:28:30 migration status: completed
> 2022-03-16 20:28:30 ERROR: tunnel replied 'ERR: resume failed - VM 104
> not running' to command 'resume 104'
> 2022-03-16 20:28:39 ERROR: migration finished with problems (duration
> 00:00:18)
> TASK ERROR: migration problems
>
I now tested with a Debian Testing (bookworm) VM and ensured it actually logs
"Free page reporting enabled" in the kernel log and you're right it fails there.
But that's only relevant for migrating a VM that got freshly started (!) on
a new (upgraded) host and then gets migrated to an old one, and that's something
we never supported anyway (besides some very light best-effort).
As the VM doesn't even crashes then, and just fails to migrate (source VM stays
running), it's not even problematic for that case; the admin can just upgrade the
qemu-server on the other node already and continue.
Same holds for live-snapshots, only a snasphot from a freshly started VM on an
already upgraded host would cause issues on rollback, but *only* on an old host,
so the same as any QEMU update would cause anyway.
So, it seems we can just enable it with 6.2 as machine guard and be done.
>
> If think this is because guest kernel balloon driver enabled it at boot
> only.
>
yeah seems so.
>
> Note that I don't think that current windows drivers already support it
> (I have looked at the source code, so even if the option is enabled at
> qemu level, it don't do nothing inside windows.
> So I think that migration will works in both direction with windows
> vms.
next prev parent reply other threads:[~2022-03-17 8:35 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-06 12:46 [pve-devel] [PATCH V2 qemu-server 0/2] " Alexandre Derumier
2022-03-06 12:46 ` [pve-devel] [PATCH V2 qemu-server 1/2] " Alexandre Derumier
2022-03-16 17:48 ` Thomas Lamprecht
2022-03-16 19:32 ` DERUMIER, Alexandre
2022-03-17 8:35 ` Thomas Lamprecht [this message]
2022-03-28 10:06 ` DERUMIER, Alexandre
2022-03-06 12:46 ` [pve-devel] [PATCH V2 qemu-server 2/2] add test for virtio-balloon free-page-reporting=on. (qemu 6.2) Alexandre Derumier
2022-04-27 9:23 ` [pve-devel] applied: [PATCH V2 qemu-server 0/2] enable balloon free-page-reporting Thomas Lamprecht
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