linux-kernel - Re: [PATCH 084/208] x86/fpu: Rename xsave.header::xstate

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Date:	Tue, 5 May 2015 20:16:13 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 084/208] x86/fpu: Rename xsave.header::xstate_bv to
 'xfeatures'


* Dave Hansen <dave.hansen@...ux.intel.com> wrote:

> On 05/05/2015 10:49 AM, Ingo Molnar wrote:
> > 'xsave.header::xstate_bv' is a misnomer - what does 'bv' stand for?
> 
> xstate_bv is what it is called in the SDM. [...]

So I'm not attached to the ::xfeatures name (we could name it 
xstate_mask, etc.) - but xstate_bv? It's really nonsensical IMHO - and 
I wanted it to be more obvious.

We could put the SDM name into a comment, next to the field 
definition? Something like, if 'xfeatures' is too long:

struct xstate_header {
        u64     xfeat;        /* xstate components,           SDM: XSTATE_BV */
        u64     xfeat_comp;   /* compacted xstate components, SDM: XCOMP_BV */
        u64     reserved[6];
} __attribute__((packed));

or so? Then if you grep for 'XSTATE_BV', you'll immediately see that 
it's called xfeat_comp.

> [...]  I'd really like to see the nomenclature match the SDM where 
> it's sensible because it says lots of things like:
> 
> 	XSAVES does not write to any parts of the XSAVE header other
> 	than the XSTATE_BV and XCOMP_BV fields.
> 
> It's nice to have code that does:
> 
> 	...->xstate_bv
> 
> to match up with that documentation IMNHO.

Where the SDM uses sensible names I'm all for that - but IMHO this is 
not such a case.

Thanks,

	Ingo
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