From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org, x86@kernel.org,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Tony Luck <tony.luck@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Rik van Riel <riel@surriel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2 8/8] x86/fpu/xstate: Restore supervisor xstates for __fpu__restore_sig()
Date: Fri, 28 Feb 2020 17:50:21 +0100 [thread overview]
Message-ID: <20200228165021.76pec2cdudmtpxeu@linutronix.de> (raw)
In-Reply-To: <6f91699c91f9ea0f527e80ed3ea2999444a8d2d1.camel@intel.com>
On 2020-02-28 08:20:27 [-0800], Yu-cheng Yu wrote:
> 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.
How large is this supervisor state at most? I guess saving the AVX512
state just to get the 2 bytes of the supervisor state at the right spot
is not really optimal.
But this is the performance division…
> I will include this in the comments.
If you do so, please state that the first hunk is only interested in the
supervisor-state bits and everything else is ignored.
> Yu-cheng
Sebastian
next prev parent reply other threads:[~2020-02-28 16:50 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 20:18 [PATCH v2 0/8] Support XSAVES supervisor states Yu-cheng Yu
2020-01-21 20:18 ` [PATCH v2 1/8] x86/fpu/xstate: Define new macros for supervisor and user xstates Yu-cheng Yu
2020-02-20 11:47 ` Borislav Petkov
2020-02-20 20:23 ` Yu-cheng Yu
2020-01-21 20:18 ` [PATCH v2 2/8] x86/fpu/xstate: Separate user and supervisor xfeatures mask Yu-cheng Yu
2020-02-21 10:34 ` Borislav Petkov
2020-01-21 20:18 ` [PATCH v2 3/8] x86/fpu/xstate: Introduce XSAVES supervisor states Yu-cheng Yu
2020-01-21 20:18 ` [PATCH v2 4/8] x86/fpu/xstate: Define new functions for clearing fpregs and xstates Yu-cheng Yu
2020-02-21 14:04 ` Borislav Petkov
2020-01-21 20:18 ` [PATCH v2 5/8] x86/fpu/xstate: Rename validate_xstate_header() to validate_xstate_header_from_user() Yu-cheng Yu
2020-02-21 14:13 ` Borislav Petkov
2020-01-21 20:18 ` [PATCH v2 6/8] x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates Yu-cheng Yu
2020-02-21 14:30 ` Borislav Petkov
2020-01-21 20:18 ` [PATCH v2 7/8] x86/fpu/xstate: Update copy_kernel_to_xregs_err() for XSAVES supervisor states Yu-cheng Yu
2020-01-21 20:18 ` [PATCH v2 8/8] x86/fpu/xstate: Restore supervisor xstates for __fpu__restore_sig() Yu-cheng Yu
2020-02-21 17:58 ` Borislav Petkov
2020-02-27 22:52 ` Yu-cheng Yu
2020-02-28 12:17 ` Borislav Petkov
2020-02-28 12:51 ` Sebastian Andrzej Siewior
2020-02-28 15:53 ` Yu-cheng Yu
2020-02-28 16:23 ` Borislav Petkov
2020-02-28 16:20 ` Yu-cheng Yu
2020-02-28 16:50 ` Sebastian Andrzej Siewior [this message]
2020-02-28 16:54 ` Yu-cheng Yu
2020-02-28 17:22 ` Borislav Petkov
2020-02-28 18:11 ` Yu-cheng Yu
2020-02-28 18:31 ` Borislav Petkov
2020-02-28 21:22 ` Yu-cheng Yu
2020-02-28 21:47 ` Borislav Petkov
2020-02-28 22:13 ` Yu-cheng Yu
2020-02-29 14:36 ` Borislav Petkov
2020-03-02 18:09 ` Yu-cheng Yu
2020-03-04 18:18 ` Yu-cheng Yu
2020-03-06 20:50 ` Borislav Petkov
2020-03-10 20:36 ` Yu-cheng Yu
2020-03-10 21:16 ` Thomas Gleixner
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