Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261590AbVCMXxR (ORCPT ); Sun, 13 Mar 2005 18:53:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261592AbVCMXxR (ORCPT ); Sun, 13 Mar 2005 18:53:17 -0500 Received: from fire.osdl.org ([65.172.181.4]:24246 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S261590AbVCMXxN (ORCPT ); Sun, 13 Mar 2005 18:53:13 -0500 Date: Sun, 13 Mar 2005 15:54:55 -0800 (PST) From: Linus Torvalds To: Pavel Machek cc: Stas Sergeev , Alan Cox , Linux kernel , Petr Vandrovec , Denis Vlasenko Subject: Re: [patch] x86: fix ESP corruption CPU bug In-Reply-To: <20050313231734.GA22635@elf.ucw.cz> Message-ID: References: <42348474.7040808@aknet.ru> <20050313201020.GB8231@elf.ucw.cz> <4234A8DD.9080305@aknet.ru> <20050313231734.GA22635@elf.ucw.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1098 Lines: 26 On Mon, 14 Mar 2005, Pavel Machek wrote: > > What about flag similar to _TIF_SYSCALL_TRACE (call it > _TIF_THIS_BEAST_USES_V86 or something), and only do the tests in the > slowpath if it is set? As normal applications do not use v86, we could > make this 0 instructions in syscall fast path... It wouldn't help you. You'd need to mix in two of the values anyway, so at most you'd save one instruction. And the cost would be that anything that has ever used vm86 mode (can you say "X server"?) would be slower. Not a good trade-off. Oh, I guess you could clear the flag when you know there's no vm86 state anywhere (easy enough, those things never nest), but then it still comes back to "extra complexity that you can get wrong, just to save a single "mov" instruction - that "mov" may have partial-register-stall issues, but still..). Linus - 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/