From: Thomas Lamprecht <t.lamprecht@proxmox.com>
To: Igor Mammedov <imammedo@redhat.com>
Cc: vit9696 <vit9696@protonmail.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Stefan Reiter <s.reiter@proxmox.com>,
qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
Richard Henderson <rth@twiddle.net>,
Laszlo Ersek <lersek@redhat.com>,
Eduardo Habkost <ehabkost@redhat.com>
Subject: Re: [PATCH 1/2] i386/acpi: fix inconsistent QEMU/OVMF device paths
Date: Mon, 1 Mar 2021 15:27:38 +0100 [thread overview]
Message-ID: <dcf40b52-e695-e516-aa26-0db30e5ee6ea@proxmox.com> (raw)
In-Reply-To: <20210301152036.0c12cbf5@redhat.com>
On 01.03.21 15:20, Igor Mammedov wrote:
> On Mon, 1 Mar 2021 08:45:53 +0100
> Thomas Lamprecht <t.lamprecht@proxmox.com> wrote:
>> On 01.03.21 08:20, Michael S. Tsirkin wrote:
>>> There are various testing efforts the reason this got undetected is
>>> because it does not affect linux guests, and even for windows
>>> they kind of recover, there's just some boot slowdown around reconfiguration.
>>> Not easy to detect automatically given windows has lots of random
>>> downtime during boot around updates etc etc.
>>>
>>
>> No, Windows does not reconfigure, this is a permanent change, one is just lucky
>> if one has a DHCP server around in the network accessible for the guest.
>> As static addresses setup on that virtual NIC before that config is gone,
>> no recovery whatsoever until manual intervention.
> Static IP's are the pain guest admin picked up to deal with so he might have to
> reconfigure guest OS when it decides to rename NICs. In this case moving
> to new QEMU is alike to updating BIOS which fixed PCI description.
> (On QEMU side we try to avoid breaking changes, but sometime it happens anyway
> and it's up guest admin to fix OS quirks)
>
heh, I agree, but users see it very differently, QEMU got updated, something
stopped working/changed/... -> QEMU at fault.
>> I meant more of a "dump HW layout to .txt file, commit to git, and ensure
>> there's no diff without and machine version bump" (very boiled down), e.g., like
>> ABI checks for kernel builds are often done by distros - albeit those are easier
>> as its quite clear what and how the kernel ABI can be used.
> ACPI tables are not considered as ABI change in QEMU, technically tables that QEMU
> generates are firmware and not version-ed (same like we don't tie anything to
> specific firmware versions).
>
> However we rarely do version ACPI changes (only when it breaks something or
> we suspect it would break and we can't accept that breakage), this time it took
> a lot of time to find out that. We try to minimize such cases as every
> versioning knob adds up to maintenance.
>
> For ACPI tables changes, QEMU has bios-tables-test, but it lets us to catch
> unintended changes only.
> Technically it's possible to keep master tables for old machine versions
> and test against it. But I'm not sure if we should do that, because some
> (most) changes are harmless or useful and should apply to all machine
> versions.
> So we will end up in the same situation, where we decide if a change
> should be versioned or not.
>
>
OK, fair enough. Many thanks for providing some rationale!
next prev parent reply other threads:[~2021-03-01 14:29 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-30 15:58 [PATCH 1/2] i386/acpi: fix inconsistent QEMU/OVMF device paths Michael S. Tsirkin
2020-07-30 15:58 ` [PATCH 2/2] arm/acpi: fix an out of spec _UID for PCI root Michael S. Tsirkin
2020-07-30 16:12 ` Philippe Mathieu-Daudé
2020-07-30 19:35 ` Laszlo Ersek
2020-07-30 20:33 ` Peter Maydell
2020-07-31 9:31 ` Igor Mammedov
2020-07-30 16:11 ` [PATCH 1/2] i386/acpi: fix inconsistent QEMU/OVMF device paths Philippe Mathieu-Daudé
2020-07-30 19:35 ` Michael S. Tsirkin
2020-07-31 2:55 ` vit9696 via
2020-07-30 19:34 ` Laszlo Ersek
2020-07-31 9:30 ` Igor Mammedov
2021-02-27 19:41 ` Thomas Lamprecht
2021-02-28 9:11 ` vit9696
2021-02-28 10:43 ` Thomas Lamprecht
2021-02-28 20:45 ` Michael S. Tsirkin
[not found] ` <x3i3TiibtrC1qTDQUKxuOA_9qvmInzVwv6RrvzzSCSj-S21gLypbbZgEbYvJSGMxC1r8RaDrnHGgRbDI7vfpA_XuDINdZej9yKCW3_Sc4YM=@protonmail.com>
2021-02-28 21:37 ` Michael S. Tsirkin
2021-02-28 20:43 ` Michael S. Tsirkin
2021-03-01 7:12 ` Thomas Lamprecht
2021-03-01 7:20 ` Michael S. Tsirkin
2021-03-01 7:45 ` Thomas Lamprecht
2021-03-01 14:20 ` Igor Mammedov
2021-03-01 14:27 ` Thomas Lamprecht [this message]
2021-03-01 20:16 ` Igor Mammedov
2021-03-01 15:31 ` Michael S. Tsirkin
2021-03-01 13:28 ` Igor Mammedov
2021-03-01 16:14 ` Michael S. Tsirkin
2021-03-01 16:28 ` Laszlo Ersek
2021-03-01 19:08 ` Igor Mammedov
2021-03-01 20:06 ` vit9696
2021-03-02 8:40 ` Laszlo Ersek
2023-04-18 9:06 zhangying (AZ) via
2023-04-19 2:48 zhangying (AZ) via
2023-04-20 14:54 ` Igor Mammedov
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