From: Dave Hansen <dave.hansen@linux.intel.com>
To: Andy Lutomirski <luto@kernel.org>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Rik van Riel <riel@surriel.com>
Cc: LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>
Subject: Re: Lazy FPU restoration / moving kernel_fpu_end() to context switch
Date: Fri, 15 Jun 2018 11:41:44 -0700 [thread overview]
Message-ID: <368b8069-0463-6161-d603-10769fd2ec57@linux.intel.com> (raw)
In-Reply-To: <CALCETrU+2mBPDfkBz1i_GT1EOJau+mzj4yOK8N0UnT2pGjiUWQ@mail.gmail.com>
On 06/15/2018 11:31 AM, Andy Lutomirski wrote:
> Using WRPKRU is easy, but,
> unless we do something very clever, actually finding PKRU in the
> in-memory fpstate image may be slightly nontrivial.
Why?
It's at a constant offset during any one boot, for sure. XSAVEC/XSAVES
can move it around, but only if you change the Requested Feature BitMap
(RFBM) that we pass to XSAVES or change the control register that
enables XSAVE states (XCR0).
We don't change XCR0 after boot, and RFBM is hard-coded to -1 as far as
I remember.
next prev parent reply other threads:[~2018-06-15 18:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-15 13:11 Jason A. Donenfeld
2018-06-15 16:25 ` Thomas Gleixner
2018-06-15 18:33 ` Brian Gerst
2018-06-15 19:34 ` Peter Zijlstra
2018-06-15 20:30 ` Jason A. Donenfeld
2018-06-18 9:44 ` Peter Zijlstra
2018-06-18 15:25 ` Jason A. Donenfeld
2018-06-15 18:31 ` Andy Lutomirski
2018-06-15 18:40 ` Rik van Riel
2018-06-15 18:41 ` Dave Hansen [this message]
2018-06-15 18:49 ` Andy Lutomirski
2018-06-15 18:48 ` Dave Hansen
2018-06-15 18:53 ` Andy Lutomirski
2018-06-15 20:27 ` Jason A. Donenfeld
2018-06-15 20:48 ` Jason A. Donenfeld
2018-06-19 11:43 ` David Laight
2018-06-19 13:08 ` Thomas Gleixner
2018-06-15 20:33 ` Jason A. Donenfeld
2018-06-15 20:42 ` Dave Hansen
2018-06-15 20:52 ` Andy Lutomirski
2018-06-15 20:56 ` Rik van Riel
2018-07-11 16:28 ` Sebastian Andrzej Siewior
2018-07-11 20:10 ` Rik van Riel
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