linux-kernel - Re: [PATCH v2 1/6] x86/fpu/xstate: Always preserve non-user xfeatures/flags in __state

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Message-ID: <ce5e2f44-144b-47bd-9f7e-02f61abed76a@intel.com>
Date: Tue, 4 Mar 2025 14:20:31 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Chao Gao <chao.gao@...el.com>, tglx@...utronix.de, x86@...nel.org,
 seanjc@...gle.com, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: peterz@...radead.org, rick.p.edgecombe@...el.com, mlevitsk@...hat.com,
 weijiang.yang@...el.com, john.allen@....com
Subject: Re: [PATCH v2 1/6] x86/fpu/xstate: Always preserve non-user
 xfeatures/flags in __state_perm

On 11/26/24 02:17, Chao Gao wrote:
> When granting userspace or a KVM guest access to an xfeature, preserve the
> entity's existing supervisor and software-defined permissions as tracked
> by __state_perm, i.e. use __state_perm to track *all* permissions even
> though all supported supervisor xfeatures are granted to all FPUs and
> FPU_GUEST_PERM_LOCKED disallows changing permissions.

Should we document what __state_perm contains either in
fpu_state_perm or xstate_get_group_perm()?

Either way:

Acked-by: Dave Hansen <dave.hansen@...el.com>