linux-kernel - Re: [PATCH v2 01/22] x86/fpu/xstate: Modify area init helper prototypes to access all the possible areas

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Date:   Mon, 7 Dec 2020 18:12:51 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>
Cc:     tglx@...utronix.de, mingo@...nel.org, luto@...nel.org,
        x86@...nel.org, len.brown@...el.com, dave.hansen@...el.com,
        jing2.liu@...el.com, ravi.v.shankar@...el.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v2 01/22] x86/fpu/xstate: Modify area init helper
 prototypes to access all the possible areas

On Thu, Nov 19, 2020 at 03:32:36PM -0800, Chang S. Bae wrote:
> The xstate infrastructure is not flexible to support dynamic areas in
> task->fpu.

task->fpu?

Do you mean the fpu member in struct thread_struct ?

> Change the fpstate_init() prototype to access task->fpu directly. It
> treats a null pointer as indicating init_fpstate, as this initial data
> does not belong to any task.

What for? Commit messages should state *why* you're doing a change - not
*what* you're doing. *What* I can more or less see, *why* is harder.

/me goes and looks forward into the patchset...

Are you going to need it for stuff like

	fpu ? fpu->state_mask : get_init_fpstate_mask()

?

If so, why don't you write *why* you're doing those changes here?


> For the compacted format, fpstate_init_xstate() now accepts the state
> component bitmap to configure XCOMP_BV.

I can see that. But why?

-- 
Regards/Gruss,
    Boris.

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