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Message-ID: <6f91699c91f9ea0f527e80ed3ea2999444a8d2d1.camel@intel.com>
Date: Fri, 28 Feb 2020 08:20:27 -0800
From: Yu-cheng Yu <yu-cheng.yu@...el.com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
Andy Lutomirski <luto@...nel.org>,
Rik van Riel <riel@...riel.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Fenghua Yu <fenghua.yu@...el.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 8/8] x86/fpu/xstate: Restore supervisor xstates for
__fpu__restore_sig()
On Fri, 2020-02-28 at 17:23 +0100, Borislav Petkov wrote:
> On Fri, Feb 28, 2020 at 07:53:38AM -0800, Yu-cheng Yu wrote:
> > Yes, saving only supervisor states is optimal, but doing XSAVES with a
> > partial RFBM changes xcomp_bv.
>
> ... and that means what exactly in plain english?
When XSAVES writes to an xsave buffer, xsave->header.xcomp_bv is set to
include only saved components, effectively changing the buffer's format.
I will include this in the comments.
Yu-cheng
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