MIPS: Basic MSA context switching support

This patch adds support for context switching the MSA vector registers.
These 128 bit vector registers are aliased with the FP registers - an
FP register accesses the least significant bits of the vector register
with which it is aliased (ie. the register with the same index). Due to
both this & the requirement that the scalar FPU must be 64-bit (FR=1) if
enabled at the same time as MSA the kernel will enable MSA & scalar FP
at the same time for tasks which use MSA. If we restore the MSA vector
context then we might as well enable the scalar FPU since the reason it
was left disabled was to allow for lazy FP context restoring - but we
just restored the FP context as it's a subset of the vector context. If
we restore the FP context and have previously used MSA then we have to
restore the whole vector context anyway (see comment in
enable_restore_fp_context for details) so similarly we might as well
enable MSA.

Thus if a task does not use MSA then it will continue to behave as
without this patch - the scalar FP context will be saved & restored as
usual. But if a task executes an MSA instruction then it will save &
restore the vector context forever more.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6431/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
index f571db371b3e..fe3b03c793e5 100644
--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -328,4 +328,74 @@
 	.endm
 #endif
 
+	.macro	msa_save_all	thread
+	st_d	0, THREAD_FPR0, \thread
+	st_d	1, THREAD_FPR1, \thread
+	st_d	2, THREAD_FPR2, \thread
+	st_d	3, THREAD_FPR3, \thread
+	st_d	4, THREAD_FPR4, \thread
+	st_d	5, THREAD_FPR5, \thread
+	st_d	6, THREAD_FPR6, \thread
+	st_d	7, THREAD_FPR7, \thread
+	st_d	8, THREAD_FPR8, \thread
+	st_d	9, THREAD_FPR9, \thread
+	st_d	10, THREAD_FPR10, \thread
+	st_d	11, THREAD_FPR11, \thread
+	st_d	12, THREAD_FPR12, \thread
+	st_d	13, THREAD_FPR13, \thread
+	st_d	14, THREAD_FPR14, \thread
+	st_d	15, THREAD_FPR15, \thread
+	st_d	16, THREAD_FPR16, \thread
+	st_d	17, THREAD_FPR17, \thread
+	st_d	18, THREAD_FPR18, \thread
+	st_d	19, THREAD_FPR19, \thread
+	st_d	20, THREAD_FPR20, \thread
+	st_d	21, THREAD_FPR21, \thread
+	st_d	22, THREAD_FPR22, \thread
+	st_d	23, THREAD_FPR23, \thread
+	st_d	24, THREAD_FPR24, \thread
+	st_d	25, THREAD_FPR25, \thread
+	st_d	26, THREAD_FPR26, \thread
+	st_d	27, THREAD_FPR27, \thread
+	st_d	28, THREAD_FPR28, \thread
+	st_d	29, THREAD_FPR29, \thread
+	st_d	30, THREAD_FPR30, \thread
+	st_d	31, THREAD_FPR31, \thread
+	.endm
+
+	.macro	msa_restore_all	thread
+	ld_d	0, THREAD_FPR0, \thread
+	ld_d	1, THREAD_FPR1, \thread
+	ld_d	2, THREAD_FPR2, \thread
+	ld_d	3, THREAD_FPR3, \thread
+	ld_d	4, THREAD_FPR4, \thread
+	ld_d	5, THREAD_FPR5, \thread
+	ld_d	6, THREAD_FPR6, \thread
+	ld_d	7, THREAD_FPR7, \thread
+	ld_d	8, THREAD_FPR8, \thread
+	ld_d	9, THREAD_FPR9, \thread
+	ld_d	10, THREAD_FPR10, \thread
+	ld_d	11, THREAD_FPR11, \thread
+	ld_d	12, THREAD_FPR12, \thread
+	ld_d	13, THREAD_FPR13, \thread
+	ld_d	14, THREAD_FPR14, \thread
+	ld_d	15, THREAD_FPR15, \thread
+	ld_d	16, THREAD_FPR16, \thread
+	ld_d	17, THREAD_FPR17, \thread
+	ld_d	18, THREAD_FPR18, \thread
+	ld_d	19, THREAD_FPR19, \thread
+	ld_d	20, THREAD_FPR20, \thread
+	ld_d	21, THREAD_FPR21, \thread
+	ld_d	22, THREAD_FPR22, \thread
+	ld_d	23, THREAD_FPR23, \thread
+	ld_d	24, THREAD_FPR24, \thread
+	ld_d	25, THREAD_FPR25, \thread
+	ld_d	26, THREAD_FPR26, \thread
+	ld_d	27, THREAD_FPR27, \thread
+	ld_d	28, THREAD_FPR28, \thread
+	ld_d	29, THREAD_FPR29, \thread
+	ld_d	30, THREAD_FPR30, \thread
+	ld_d	31, THREAD_FPR31, \thread
+	.endm
+
 #endif /* _ASM_ASMMACRO_H */