linux-kernel - Re: [GIT PULL] KVM: x86: Misc changes for 6.20

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Message-ID: <aYpPay9AuD3KkYfr@google.com>
Date: Mon, 9 Feb 2026 13:19:39 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: x86: Misc changes for 6.20

On Mon, Feb 09, 2026, Paolo Bonzini wrote:
> On Sat, Feb 7, 2026 at 5:10 AM Sean Christopherson <seanjc@...gle.com> wrote:
> >  - Add WARNs to guard against modifying KVM's CPU caps outside of the intended
> >    setup flow, as nested VMX in particular is sensitive to unexpected changes
> >    in KVM's golden configuration.
> 
> Possible follow-up: does it make sense to sync kvm_caps.supported_xss
> by calling kvm_setup_xss_caps() from kvm_finalize_cpu_caps()?

Ha!  I did that in v1[*], but Xiaoyao didn't like that it hid the XSS setup, which
very technically aren't part of kvm_cpu_caps.  For the current code base, the pros
and cons of each approach seem to largely cancel each other out, so I think my vote
is to keep things as-is for now, and revisit things if/when we end up with more
common code that needs to run right before kvm_finalize_cpu_caps().

[*] https://lore.kernel.org/all/20260123221542.2498217-2-seanjc@google.com