> On 9. Mar 2026, at 07:33, Khushit Shah <[email protected]> wrote:
>
>
>
>> On 9 Mar 2026, at 11:27 AM, Mohamed Mediouni <[email protected]>
>> wrote:
>>
>> Hi,
>>
>> Ugh about this one, but am still convinced that a machine model version
>> is _the_ right way to deal with this. Will this be backported to Linux LTSes
>> on the KVM side?
>>
>> Or alternatively, what are the odds of having it fit as a CPU flag?
>> For example -cpu host,x2apic-suppress-eoi-broadcast=on.
>
>
> Hi,
>
> Thanks for the review.
>
> Regarding the -cpu flag: This doesn't feel right because SEOIB is an
> accelerator-specific (KVM)
> value. Tying it to the CPU suggests an architectural feature that wouldn't
> apply to TCG. What
> specifically feels off about keeping it as a KVM/Machine property?
Hello,
The reason why I considered this is that QEMU CPU models are versioned
separately from the machine
model, with an understanding that an older CPU model might not work on an older
KVM.
And with a common CPU model being also a requirement for live migration too.
This has historically been generally leveraged for security mitigations but it
could be a good fit here.
That could provide a path towards it becoming the default when -cpu host on a
supported kernel (which doesn’t entail having LM support), while keeping LM
working and having it stepped in with newer CPU model versions, which people
will update to more often than new kernels. Maybe the best shape could be a
no_seoib flag for older predefined CPU models…
My concern is primarily somebody installing a new QEMU, running
qemu-system-x86_64 -M q35,kernel-irqchip=split [whatever], which would pick the
latest machine model version and fail straight away if this is rolled as part
of a new machine model if running on a kernel without the KVM side merged in.
And having a custom flag not turned on by default for a long time for this
comes with the risk that almost nobody will enable it instead of it being
eventually phased in as the default configuration… Or maybe it matters a lot
less because kernel-irqchip=split is not the default today anyway?
Thank you,
-Mohamed
>
> Regarding the backports: The KVM kernel side is currently in 6.18 and 6.19. I
> haven’t yet came
> around to manually backported it to the older stable releases yet.
>
> Thanks,
> Khushit.
