linux-kernel - Re: [PATCH v2 06/39] x86/fpu: Add helper for modifying xstate

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Message-ID: <62c6c3a7-3bd2-69ee-36cd-341e11c43978@intel.com>
Date:   Tue, 4 Oct 2022 07:18:43 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "keescook@...omium.org" <keescook@...omium.org>
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Subject: Re: [PATCH v2 06/39] x86/fpu: Add helper for modifying xstate

On 10/3/22 13:05, Edgecombe, Rick P wrote:
> The CET state is xsaves managed. It gets lazily restored before
> returning to userspace with the rest of the fpu stuff. This function
> will force restore all the fpu state to the registers early and lock
> them from being automatically saved/restored. Then the tasks CET state
> can be modified in the MSRs, before unlocking the fpregs. Last time I
> tried to modify the state directly in the xsave buffer when it was
> efficient, but it had issues and Thomas suggested this.

Can you get the gist of this in a comment, please?