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Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action
From: |
Markus Armbruster |
Subject: |
Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action |
Date: |
Thu, 17 Jun 2021 13:09:08 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) |
Valeriy Vdovin <valeriy.vdovin@virtuozzo.com> writes:
> On Thu, Jun 17, 2021 at 07:22:36AM +0200, Markus Armbruster wrote:
>> Valeriy Vdovin <valeriy.vdovin@virtuozzo.com> writes:
>>
>> > Introducing new qapi method 'query-kvm-cpuid'. This method can be used to
>>
>> It's actually a QMP command. There are no "qapi methods".
>>
>> > get virtualized cpu model info generated by QEMU during VM initialization
>> > in
>> > the form of cpuid representation.
>> >
>> > Diving into more details about virtual cpu generation: QEMU first parses
>> > '-cpu'
>>
>> virtual CPU
>>
>> > command line option. From there it takes the name of the model as the
>> > basis for
>> > feature set of the new virtual cpu. After that it uses trailing '-cpu'
>> > options,
>> > that state if additional cpu features should be present on the virtual cpu
>> > or
>> > excluded from it (tokens '+'/'-' or '=on'/'=off').
>> > After that QEMU checks if the host's cpu can actually support the derived
>> > feature set and applies host limitations to it.
>> > After this initialization procedure, virtual cpu has it's model and
>> > vendor names, and a working feature set and is ready for identification
>> > instructions such as CPUID.
>> >
>> > Currently full output for this method is only supported for x86 cpus.
>>
>> Not sure about "currently": the interface looks quite x86-specific to me.
>>
> Yes, at some point I was thinking this interface could become generic,
> but does not seem possible, so I'll remove this note.
>
>> The commit message doesn't mention KVM except in the command name. The
>> schema provides the command only if defined(CONFIG_KVM).
>>
>> Can you explain why you need the restriction to CONFIG_KVM?
>>
> This CONFIG_KVM is used as a solution to a broken build if --disable-kvm
> flag is set. I was choosing between this and writing empty implementation into
> kvm-stub.c
If the command only makes sense for KVM, then it's named correctly, but
the commit message lacks a (brief!) explanation why it only makes for
KVM.
If it just isn't implemented for anything but KVM, then putting "kvm"
into the command name is a bad idea. Also, the commit message should
briefly note the restriction to KVM.
Pick one :)
[...]
- [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Valeriy Vdovin, 2021/06/03
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Vladimir Sementsov-Ogievskiy, 2021/06/03
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Markus Armbruster, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Valeriy Vdovin, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action,
Markus Armbruster <=
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Claudio Fontana, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Markus Armbruster, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Valeriy Vdovin, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Claudio Fontana, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Eduardo Habkost, 2021/06/17
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Markus Armbruster, 2021/06/18
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Eduardo Habkost, 2021/06/18
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Markus Armbruster, 2021/06/21
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Claudio Fontana, 2021/06/21
- Re: [PATCH v9] qapi: introduce 'query-kvm-cpuid' action, Eduardo Habkost, 2021/06/21