Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946650AbbEVJic (ORCPT ); Fri, 22 May 2015 05:38:32 -0400 Received: from eddie.linux-mips.org ([148.251.95.138]:50561 "EHLO cvs.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945907AbbEVJi0 (ORCPT ); Fri, 22 May 2015 05:38:26 -0400 Date: Fri, 22 May 2015 11:38:13 +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: <20150522093812.GH6941@linux-mips.org> References: <20150519211222.35859.52798.stgit@ubuntu-yegoshin> <20150519211351.35859.80332.stgit@ubuntu-yegoshin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150519211351.35859.80332.stgit@ubuntu-yegoshin> 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: 2397 Lines: 66 On Tue, May 19, 2015 at 02:13:51PM -0700, Leonid Yegoshin wrote: > During thread cloning the new (child) thread should have MSA disabled even > at first thread entry. So, the code to disable MSA is moved from macro > 'switch_to' to assembler function 'resume' before it switches kernel stack > to 'next' (new) thread. Call of 'disable_msa' after 'resume' in 'switch_to' > macro never called a first time entry into thread. > > Signed-off-by: Leonid Yegoshin > --- > arch/mips/include/asm/switch_to.h | 1 - > arch/mips/kernel/r4k_switch.S | 6 ++++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/mips/include/asm/switch_to.h b/arch/mips/include/asm/switch_to.h > index e92d6c4b5ed1..0d0f7f8f8b3a 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) \ > diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S > index 04cbbde3521b..7dbb64656bfe 100644 > --- a/arch/mips/kernel/r4k_switch.S > +++ b/arch/mips/kernel/r4k_switch.S > @@ -25,6 +25,7 @@ > /* preprocessor replaces the fp in ".set fp=64" with $30 otherwise */ > #undef fp > > +#define t4 $12 You're kidding, right? > /* > * Offset to the current process status flags, the first 32 bytes of the > * stack are not used. > @@ -73,6 +74,11 @@ > cfc1 t1, fcr31 > msa_save_all a0 > .set pop /* SET_HARDFLOAT */ > + li t4, MIPS_CONF5_MSAEN > + mfc0 t3, CP0_CONFIG, 5 > + or t3, t3, t4 > + xor t3, t3, t4 > + mtc0 t3, CP0_CONFIG, 5 > > sw t1, THREAD_FCR31(a0) > b 2f Just move the call to finish_arch_switch(). 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 -- 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/