Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933393AbaBAVRe (ORCPT ); Sat, 1 Feb 2014 16:17:34 -0500 Received: from science.horizon.com ([71.41.210.146]:41364 "HELO science.horizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932270AbaBAVRN (ORCPT ); Sat, 1 Feb 2014 16:17:13 -0500 Date: 1 Feb 2014 16:17:10 -0500 Message-ID: <20140201211710.20281.qmail@science.horizon.com> From: "George Spelvin" To: hpa@zytor.com, torvalds@linux-foundation.org Subject: Re: [PATCH] Make math_state_restore() save and restore the interrupt flag Cc: jack@suse.cz, linux-kernel@vger.kernel.org, linux@horizon.com, maarten-baert@hotmail.com, mingo@kernel.org, nate@thatsmathematics.com, priikone@iki.fi, sbsiddha@gmail.com, stable@vger.kernel.org, tglx@linutronix.de, x86@kernel.org In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > .. which *does* actually bring up something that might work, and might > be a good idea: remove the "restore math state or set TS" from the > normal kernel paths *entirely*, and move it to the "return to user > space" phase. This definitely seems much more sensible. For processors without optimized context save/restore, the decision whether to restore eagerly is best made once the kernel has decided what it's returning *to*. >From an interrupt handler, there are now three cases: 1) FPU not in use, available for immediate use. 2) FPU in use by user-space; save to before using. 3) FPU in use by kernel code; may not be used (unless we want to add nested FPU state save hair). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/