linux-kernel - Re: [PATCH v2 0/9] x86/xsaves: Fix XSAVES known issues

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Message-ID: <56CF6AB8.1050803@linux.intel.com>
Date:	Thu, 25 Feb 2016 12:57:28 -0800
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Yu-cheng Yu <yu-cheng.yu@...el.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Cc:	Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v2 0/9] x86/xsaves: Fix XSAVES known issues

On 02/25/2016 12:26 PM, Yu-cheng Yu wrote:
> Patch 9 re-enables XSAVES.

Could we also add one more thing to this: A big, fat warning that
supervisor states are not supported?  We might get that from an eventual
use of xfeature_uncompacted_offset(), but we need something that's very
clear.

I just don't want somebody coming along and shoving a supervisor state
in to XCR0 and expecting it to work just because we have XSAVES support
itself.  That might happen in-tree or out-of-tree as things get prototyped.