From mboxrd@z Thu Jan 1 00:00:00 1970 From: nerv@dawncrow.de (=?ISO-8859-1?Q?Andr=E9_Hentschel?=) Date: Mon, 22 Apr 2013 23:07:35 +0200 Subject: [PATCHv2] arm: Preserve TPIDRURW on context switch In-Reply-To: <20130422151836.GA15665@mudshark.cambridge.arm.com> References: <517168BB.3070903@dawncrow.de> <20130422143616.GP14496@n2100.arm.linux.org.uk> <20130422151836.GA15665@mudshark.cambridge.arm.com> Message-ID: <5175A697.3080308@dawncrow.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 after the last context-switch, meaning that tp_value is out-of-date.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? Do i need any further flag checks in copy_thread or can i use the compile-time check to add unconditional code?