linux-kernel - Re: [PATCH v2] KVM: x86: Do not return host topology information from KVM_GET_SUPPORTED

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Message-ID: <CALMp9eQe__xPe9JjgpN_jq-zB2UUqBKYrrMpGvJOjohT=gK2=Q@mail.gmail.com>
Date:   Thu, 26 Jan 2023 12:45:58 -0800
From:   Jim Mattson <jmattson@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        seanjc@...gle.com, stable@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86: Do not return host topology information from KVM_GET_SUPPORTED_CPUID

On Thu, Jan 26, 2023 at 9:47 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 1/26/23 17:06, Jim Mattson wrote:
> >>> Sadly, there isn't a single kernel involved. People running our VMM on
> >>> their desktops are going to be impacted as soon as this patch hits
> >>> that distro. (I don't know if I can say which distro that is.) So, now
> >>> we have to get the VMM folks to urgently accommodate this change and
> >>> get a new distribution out.
> >>
> >> Ok, this is what is needed to make a more informed choice.  To be clear,
> >> this is _still_ not public (for example it's not ChromeOS), so there is
> >> at least some control on what version of the VMM they use?  Would it
> >> make sense to buy you a few months by deferring this patch to Linux 6.3-6.5?
> >
> > Mainline isn't a problem. I'm more worried about 5.19 LTS.
>
> 5.19 is not LTS, is it?  This patch is only in 6.1.7 and 6.1.8 as far as
> stable kernels is concerned, should I ask Greg to revert it there?

It came to my attention when commit 196c6f0c3e21 ("KVM: x86: Do not
return host topology information from KVM_GET_SUPPORTED_CPUID") broke
some of our tests under 5.10 LTS.

If it isn't bound for linux-5.19-y, then we have some breathing room.