linux-kernel - [PATCH 1/2] MIPS: MSA: bugfix - disable MSA during thread switch correctly

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Message-ID: <20150519211351.35859.80332.stgit@ubuntu-yegoshin>
Date:	Tue, 19 May 2015 14:13:51 -0700
From:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
To:	<linux-mips@...ux-mips.org>, <rusty@...tcorp.com.au>,
	<alexinbeijing@...il.com>, <paul.burton@...tec.com>,
	<david.daney@...ium.com>, <alex@...x-smith.me.uk>,
	<linux-kernel@...r.kernel.org>, <ralf@...ux-mips.org>,
	<james.hogan@...tec.com>, <markos.chandras@...tec.com>,
	<macro@...ux-mips.org>, <eunb.song@...sung.com>,
	<manuel.lauss@...il.com>, <andreas.herrmann@...iumnetworks.com>
Subject: [PATCH 1/2] MIPS: MSA: bugfix - disable MSA during thread switch
 correctly

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 <Leonid.Yegoshin@...tec.com>
---
 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
 /*
  * 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

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