linux-kernel - Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation

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Date:	Thu, 06 Aug 2015 09:03:22 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Peter Anvin <hpa@...or.com>, Denys Vlasenko <dvlasenk@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
	bp@...en8.de, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	fenghua.yu@...el.com, x86@...nel.org
Subject: Re: [PATCH] x86, fpu: correct XSAVE xstate size calculation

Here's a correction about what we do today, and it's an important point.
 The code I was ripping out in the patch was *really* just for the
XSAVES/compacted case, does *NOT* do anything today since we've disabled
XSAVES.

So perhaps the title here should be:

	[PATCH] x86, fpu: correct XSAVES xstate size calculation

/* Option 1, what we have today */

	if (!cpu_has_xsaves) {
		cpuid(0xD0, 0, &total_blob_size, ...);
		return;
	}
	/*
	 * This breaks if offset[i]+size[i] != offset[i+1]
	 * or if alignment is in play.  Silly hardware breaks
	 * this today.
	 */
	for (i = 0; i < nr_xstates; i++) {
		if (!enabled_xstate(i))
			continue;
		total_blob_size += xstate_sizes[i];
	}

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