MIPS: save/restore MSACSR register on context switch

I added a field for the MSACSR register in struct mips_fpu_struct, but
never actually made use of it... This is a clear bug. Save and restore
the MSACSR register along with the vector registers.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7300/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/asmmacro.h

@@ -10,6 +10,7 @@
 
 #include <asm/hazards.h>
 #include <asm/asm-offsets.h>
+#include <asm/msa.h>
 
 #ifdef CONFIG_32BIT
 #include <asm/asmmacro-32.h>
@@ -378,9 +379,19 @@
 	st_d	29, THREAD_FPR29, \thread
 	st_d	30, THREAD_FPR30, \thread
 	st_d	31, THREAD_FPR31, \thread
+	.set	push
+	.set	noat
+	cfcmsa	$1, MSA_CSR
+	sw	$1, THREAD_MSA_CSR(\thread)
+	.set	pop
 	.endm
 
 	.macro	msa_restore_all	thread
+	.set	push
+	.set	noat
+	lw	$1, THREAD_MSA_CSR(\thread)
+	ctcmsa	MSA_CSR, $1
+	.set	pop
 	ld_d	0, THREAD_FPR0, \thread
 	ld_d	1, THREAD_FPR1, \thread
 	ld_d	2, THREAD_FPR2, \thread

arch/mips/kernel/asm-offsets.c

@@ -234,6 +234,7 @@ void output_thread_fpu_defines(void)
 	       thread.fpu.fpr[31].val64[FPR_IDX(64, 0)]);
 
 	OFFSET(THREAD_FCR31, task_struct, thread.fpu.fcr31);
+	OFFSET(THREAD_MSA_CSR, task_struct, thread.fpu.msacsr);
 	BLANK();
 }