linux-kernel - Re: [PATCH 1/4] x86/fpu: Clear XSTATE_BV[i] in save state whenever XFD[i]=1

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Message-ID: <CALMp9eSWwjZ83VQXRSD3ciwHmtaK5_i-941KdiAv9V9eU20B8g@mail.gmail.com>
Date: Mon, 5 Jan 2026 16:54:37 -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, 
	x86@...nel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/4] x86/fpu: Clear XSTATE_BV[i] in save state whenever XFD[i]=1

On Thu, Jan 1, 2026 at 1:13 AM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> From: Sean Christopherson <seanjc@...gle.com>
> ...
> +       /*
> +        * KVM's guest ABI is that setting XFD[i]=1 *can* immediately revert
> +        * the save state to initialized.

This comment suggests that an entry should be added to
Documentation/virt/kvm/x86/errata.rst.