From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946658Ab3BHPs2 (ORCPT ); Fri, 8 Feb 2013 10:48:28 -0500 Received: from fw-tnat.cambridge.arm.com ([217.140.96.21]:58794 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1760152Ab3BHPs0 (ORCPT ); Fri, 8 Feb 2013 10:48:26 -0500 Date: Fri, 8 Feb 2013 15:48:09 +0000 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" , Greg KH Subject: Re: [PATCH] arm: Preserve TPIDRURW on context switch Message-ID: <20130208154809.GF3495@mudshark.cambridge.arm.com> References: <5112DC7E.4020108@dawncrow.de> <20130206225150.GL17833@n2100.arm.linux.org.uk> <5112E0C3.1080706@dawncrow.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5112E0C3.1080706@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 On Wed, Feb 06, 2013 at 11:01:23PM +0000, André Hentschel wrote: > Am 06.02.2013 23:51, schrieb Russell King - ARM Linux: > > On Wed, Feb 06, 2013 at 11:43:10PM +0100, André Hentschel wrote: > >> 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. > > > > I'd prefer this was done a little more sensitively to those CPUs where > > loads/stores are expensive, namely: > > > >> + > >> + @ preserve TPIDRURW register state > >> + get_tls2 r3, r4, r5 > >> + str r3, [r1, #TI_TP2_VALUE] > >> + ldr r3, [r2, #TI_TP2_VALUE] > >> + set_tls2 r3, r4, r5 > > > > those two loads/stores get omitted from the thread switching if the CPU > > doesn't support it. Do you think that's something you could do? > > No, i'm not sure how to improve this. How does the process can continue, can you or someone else fix that and add his Signed-off-by? How about something like the (completely untested) diff below? Andre: if this works for you, I'm happy to write a commit message etc. Cheers, Will --->8 diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index cddda1f..d90be6d 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -58,7 +58,7 @@ struct thread_info { struct cpu_context_save cpu_context; /* cpu context */ __u32 syscall; /* syscall number */ __u8 used_cp[16]; /* thread used copro */ - unsigned long tp_value; + unsigned long tp_value[2]; /* TLS registers */ #ifdef CONFIG_CRUNCH struct crunch_state crunchstate; #endif diff --git a/arch/arm/include/asm/tls.h b/arch/arm/include/asm/tls.h index 73409e6..e1b09d32 100644 --- a/arch/arm/include/asm/tls.h +++ b/arch/arm/include/asm/tls.h @@ -6,9 +6,9 @@ .endm .macro set_tls_v6k, tp, tmp1, tmp2 - mcr p15, 0, \tp, c13, c0, 3 @ set TLS register - mov \tmp1, #0 - mcr p15, 0, \tmp1, c13, c0, 2 @ clear user r/w TLS register + ldrd \tmp1, \tmp2, [\tp] + mcr p15, 0, \tmp1, c13, c0, 3 @ set user r/o TLS register + mcr p15, 0, \tmp2, c13, c0, 2 @ set user r/w TLS register .endm .macro set_tls_v6, tp, tmp1, tmp2 @@ -16,15 +16,17 @@ ldr \tmp1, [\tmp1, #0] mov \tmp2, #0xffff0fff tst \tmp1, #HWCAP_TLS @ hardware TLS available? - mcrne p15, 0, \tp, c13, c0, 3 @ yes, set TLS register - movne \tmp1, #0 - mcrne p15, 0, \tmp1, c13, c0, 2 @ clear user r/w TLS register - streq \tp, [\tmp2, #-15] @ set TLS value at 0xffff0ff0 + ldrdne \tmp1, \tmp2, [\tp] + ldreq \tmp1, [\tp] + mcrne p15, 0, \tmp1, c13, c0, 3 @ yes, set user r/o TLS register + mcrne p15, 0, \tmp2, c13, c0, 2 @ set user r/w TLS register + streq \tmp1, [\tmp2, #-15] @ set TLS value at 0xffff0ff0 .endm .macro set_tls_software, tp, tmp1, tmp2 - mov \tmp1, #0xffff0fff - str \tp, [\tmp1, #-15] @ set TLS value at 0xffff0ff0 + ldr \tmp1, [\tp] + mov \tmp2, #0xffff0fff + str \tmp1, [\tmp2, #-15] @ set TLS value at 0xffff0ff0 .endm #endif diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 0f82098..a0a8fe3 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -728,7 +728,7 @@ ENTRY(__switch_to) UNWIND(.fnstart ) UNWIND(.cantunwind ) add ip, r1, #TI_CPU_SAVE - ldr r3, [r2, #TI_TP_VALUE] + add r3, r2, #TI_TP_VALUE ARM( stmia ip!, {r4 - sl, fp, sp, lr} ) @ Store most regs on stack THUMB( stmia ip!, {r4 - sl, fp} ) @ Store most regs on stack THUMB( str sp, [ip], #4 ) diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index c6dec5f..ea298d2 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -400,7 +400,7 @@ copy_thread(unsigned long clone_flags, unsigned long stack_start, clear_ptrace_hw_breakpoint(p); if (clone_flags & CLONE_SETTLS) - thread->tp_value = childregs->ARM_r3; + thread->tp_value[0] = childregs->ARM_r3; thread_notify(THREAD_NOTIFY_COPY, thread); diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 03deeff..2bc1514 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -849,7 +849,7 @@ long arch_ptrace(struct task_struct *child, long request, #endif case PTRACE_GET_THREAD_AREA: - ret = put_user(task_thread_info(child)->tp_value, + ret = put_user(task_thread_info(child)->tp_value[0], datap); break; diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index b0179b8..08b0db9 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -588,7 +588,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs) return regs->ARM_r0; case NR(set_tls): - thread->tp_value = regs->ARM_r0; + thread->tp_value[0] = regs->ARM_r0; if (tls_emu) return 0; if (has_tls_reg) { @@ -706,7 +706,7 @@ static int get_tp_trap(struct pt_regs *regs, unsigned int instr) int reg = (instr >> 12) & 15; if (reg == 15) return 1; - regs->uregs[reg] = current_thread_info()->tp_value; + regs->uregs[reg] = current_thread_info()->tp_value[0]; regs->ARM_pc += 4; return 0; }