Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756555Ab3DWJPv (ORCPT ); Tue, 23 Apr 2013 05:15:51 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:46368 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756003Ab3DWJPt (ORCPT ); Tue, 23 Apr 2013 05:15:49 -0400 Date: Tue, 23 Apr 2013 10:15:36 +0100 From: Will Deacon To: =?iso-8859-1?Q?Andr=E9?= Hentschel Cc: Russell King - ARM Linux , "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" Subject: Re: [PATCHv2] arm: Preserve TPIDRURW on context switch Message-ID: <20130423091536.GB17593@mudshark.cambridge.arm.com> References: <517168BB.3070903@dawncrow.de> <20130422143616.GP14496@n2100.arm.linux.org.uk> <20130422151836.GA15665@mudshark.cambridge.arm.com> <5175A697.3080308@dawncrow.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5175A697.3080308@dawncrow.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2165 Lines: 46 On Mon, Apr 22, 2013 at 10:07:35PM +0100, Andr? Hentschel wrote: > Am 22.04.2013 17:18, schrieb Will Deacon: > > On Mon, Apr 22, 2013 at 03:36:16PM +0100, Russell King - ARM Linux wrote: > >> On Fri, Apr 19, 2013 at 05:54:35PM +0200, Andr? Hentschel wrote: > >>> From: =?UTF-8?q?Andr=C3=A9=20Hentschel?= > >>> > >>> There are more and more applications coming to WinRT, Wine could support them, > >>> but mostly they expect to have the thread environment block (TEB) in TPIDRURW. > >>> This register must be preserved per thread instead of being cleared. > >>> > >>> Signed-off-by: Andr? Hentschel > >> > >> This actually makes things less efficient all round, because you > >> now use the value immediately after loading, which means it will cause > >> pipeline stalls, certainly on older CPUs. > >> > >> Could you please rework the patch to try avoiding soo many modifications > >> to the way things have been done here? > > > > copy_thread also needs updating so that the *register* value for the parent > > is copied to the child, since the parent may have written the register > > after the last context-switch, meaning that tp_value is out-of-date. > > Thank you both for reviewing. > > I guess you mostly mean "ldr r6, [r2, #TI_CPU_DOMAIN]". > I just thought about old CPUs and remembered again that we at Wine > need that patch only on v7 (and later). So is it ok to introduce a set_tls_v7 > in tls.h and make use of CONFIG_CPU_V7 compile-time check in > the changed files and in the copy_thread function? No, we should support this feature on any CPU with the TPIDRURW register, otherwise it's going to get really confusing for userspace. > Do i need any further flag checks in copy_thread or can i use the > compile-time check to add unconditional code? You could introduce `get' tls functions, which don't do anything for CPUs without the relevant registers. Will -- 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/