From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752029AbbLHStJ (ORCPT ); Tue, 8 Dec 2015 13:49:09 -0500 Received: from www.linutronix.de ([62.245.132.108]:51836 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751889AbbLHStH (ORCPT ); Tue, 8 Dec 2015 13:49:07 -0500 Date: Tue, 8 Dec 2015 19:48:19 +0100 (CET) From: Thomas Gleixner To: Dave Hansen cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, dave.hansen@linux.intel.com Subject: Re: [PATCH 30/34] x86, fpu: allow setting of XSAVE state In-Reply-To: <20151204011506.7A3C77FA@viggo.jf.intel.com> Message-ID: References: <20151204011424.8A36E365@viggo.jf.intel.com> <20151204011506.7A3C77FA@viggo.jf.intel.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Dec 2015, Dave Hansen wrote: > > From: Dave Hansen > > We want to modify the Protection Key rights inside the kernel, so > we need to change PKRU's contents. But, if we do a plain > 'wrpkru', when we return to userspace we might do an XRSTOR and > wipe out the kernel's 'wrpkru'. So, we need to go after PKRU in > the xsave buffer. > > We do this by: > 1. Ensuring that we have the XSAVE registers (fpregs) in the > kernel FPU buffer (fpstate) > 2. Looking up the location of a given state in the buffer > 3. Filling in the stat > 4. Ensuring that the hardware knows that state is present there > (basically that the 'init optimization' is not in place). > 5. Copying the newly-modified state back to the registers if > necessary. > > Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f41.google.com (mail-wm0-f41.google.com [74.125.82.41]) by kanga.kvack.org (Postfix) with ESMTP id 988CA6B0255 for ; Tue, 8 Dec 2015 13:49:09 -0500 (EST) Received: by wmww144 with SMTP id w144so41742439wmw.0 for ; Tue, 08 Dec 2015 10:49:09 -0800 (PST) Received: from Galois.linutronix.de (linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id n16si5938416wjw.236.2015.12.08.10.49.08 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 08 Dec 2015 10:49:08 -0800 (PST) Date: Tue, 8 Dec 2015 19:48:19 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCH 30/34] x86, fpu: allow setting of XSAVE state In-Reply-To: <20151204011506.7A3C77FA@viggo.jf.intel.com> Message-ID: References: <20151204011424.8A36E365@viggo.jf.intel.com> <20151204011506.7A3C77FA@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, dave.hansen@linux.intel.com On Thu, 3 Dec 2015, Dave Hansen wrote: > > From: Dave Hansen > > We want to modify the Protection Key rights inside the kernel, so > we need to change PKRU's contents. But, if we do a plain > 'wrpkru', when we return to userspace we might do an XRSTOR and > wipe out the kernel's 'wrpkru'. So, we need to go after PKRU in > the xsave buffer. > > We do this by: > 1. Ensuring that we have the XSAVE registers (fpregs) in the > kernel FPU buffer (fpstate) > 2. Looking up the location of a given state in the buffer > 3. Filling in the stat > 4. Ensuring that the hardware knows that state is present there > (basically that the 'init optimization' is not in place). > 5. Copying the newly-modified state back to the registers if > necessary. > > Signed-off-by: Dave Hansen Reviewed-by: Thomas Gleixner -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org