Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757761AbbEVXUi (ORCPT ); Fri, 22 May 2015 19:20:38 -0400 Received: from eddie.linux-mips.org ([148.251.95.138]:58155 "EHLO cvs.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756983AbbEVXUg (ORCPT ); Fri, 22 May 2015 19:20:36 -0400 Date: Sat, 23 May 2015 01:20:19 +0200 From: Ralf Baechle To: Leonid Yegoshin Cc: linux-mips@linux-mips.org, rusty@rustcorp.com.au, alexinbeijing@gmail.com, paul.burton@imgtec.com, david.daney@cavium.com, alex@alex-smith.me.uk, linux-kernel@vger.kernel.org, james.hogan@imgtec.com, markos.chandras@imgtec.com, macro@linux-mips.org, eunb.song@samsung.com, manuel.lauss@gmail.com, andreas.herrmann@caviumnetworks.com Subject: Re: [PATCH 1/2] MIPS: MSA: bugfix - disable MSA during thread switch correctly Message-ID: <20150522232019.GA10556@linux-mips.org> References: <20150519211222.35859.52798.stgit@ubuntu-yegoshin> <20150519211351.35859.80332.stgit@ubuntu-yegoshin> <20150522093812.GH6941@linux-mips.org> <555F776E.3070904@imgtec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <555F776E.3070904@imgtec.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2355 Lines: 64 On Fri, May 22, 2015 at 11:37:34AM -0700, Leonid Yegoshin wrote: > On 05/22/2015 02:38 AM, Ralf Baechle wrote: > >Just move the call to finish_arch_switch(). > > It might be a problem later, then a correct MSA partiton starts working. It > should be tight to saving MSA registers in that case. > > >Your rewrite also dropped the if (cpu_has_msa) condition from > >disable_msa() probably causing havoc on lots of CPUs which will likely not > >decode the set bits of the MFC0/MTC0 instructions thus end up accessing > >Config0. Ralf > > Right before this chunk of code there is a saving MSA registers. Does it > causing a havoc or else? > > May I ask you to look into switch_to macro to figure out how "if > (cpu_has_msa)" check works in this case? Ah sorry I now see that your added code is not executed for all CPUs but only those having MSA. So then it's safe. Still I don't stylistically like defining the register t4 in the middle of the code. Below my suggested patch. It's advantage is that for non-MSA platforms the call to disable_msa() will be removed entirely. Something like Paul's http://patchwork.linux-mips.org/patch/10111/ (assuming it's correct and tested) seems like a full cleanup but it's way too complex for 4.1 or the stable kernels. Ralf Signed-off-by: Ralf Baechle arch/mips/include/asm/switch_to.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/include/asm/switch_to.h b/arch/mips/include/asm/switch_to.h index e92d6c4b..7163cd7 100644 --- a/arch/mips/include/asm/switch_to.h +++ b/arch/mips/include/asm/switch_to.h @@ -104,7 +104,6 @@ do { \ if (test_and_clear_tsk_thread_flag(prev, TIF_USEDMSA)) \ __fpsave = FP_SAVE_VECTOR; \ (last) = resume(prev, next, task_thread_info(next), __fpsave); \ - disable_msa(); \ } while (0) #define finish_arch_switch(prev) \ @@ -122,6 +121,7 @@ do { \ if (cpu_has_userlocal) \ write_c0_userlocal(current_thread_info()->tp_value); \ __restore_watch(); \ + disable_msa(); \ } while (0) #endif /* _ASM_SWITCH_TO_H */ -- 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/