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SubjectRe: [PATCH] KVM: x86: disable on 32-bit unless CONFIG_BROKEN
On 29/09/2022 15.52, Maxim Levitsky wrote:
> On Thu, 2022-09-29 at 15:26 +0200, Paolo Bonzini wrote:
>> On 9/28/22 19:55, Sean Christopherson wrote:
>>>> As far as my opinion goes I do volunteer to test this code more often,
>>>> and I do not want to see the 32 bit KVM support be removed*yet*.
>>>
>>> Yeah, I 100% agree that it shouldn't be removed until we have equivalent test
>>> coverage. But I do think it should an "off-by-default" sort of thing. Maybe
>>> BROKEN is the wrong dependency though? E.g. would EXPERT be a better option?
>>
>> Yeah, maybe EXPERT is better but I'm not sure of the equivalent test
>> coverage. 32-bit VMX/SVM kvm-unit-tests are surely a good idea, but
>> what's wrong with booting an older guest?
>
>>From my point of view, using the same kernel source for host and the guest
> is easier because you know that both kernels behave the same.
>
> About EXPERT, IMHO these days most distros already dropped 32 bit suport thus anyway
> one needs to compile a recent 32 bit kernel manually - thus IMHO whoever
> these days compiles a 32 bit kernel, knows what they are doing.
>
> I personally would wait few more releases when there is a pressing reason to remove
> this support.

FWIW, from the QEMU perspective, it would be very helpful to remove 32-bit
KVM support from the kernel. The QEMU project currently struggles badly with
keeping everything tested in the CI in a reasonable amount of time. The
32-bit KVM kernel support is the only reason to keep the qemu-system-i386
binary around - everything else can be covered with the qemu-system-x86_64
binary that is a superset of the -i386 variant (except for the KVM part as
far as I know).
Sure, we could also drop qemu-system-i386 from the CI without dropping the
32-bit KVM code in the kernel, but I guess things will rather bitrot there
even faster in that case, so I'd appreciate if the kernel could drop the
32-bit in the near future, too.

Thomas

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