diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2014-01-27 15:23:11 +0000 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2014-03-26 23:09:10 +0100 |
| commit | 1db1af84d6df99a8e5d6ddea8c7b5c1327c9a620 (patch) | |
| tree | 72865fad6fa4bcfabe94ae3642a58bf28a533181 /arch/mips/include/asm/switch_to.h | |
| parent | a5e9a69e2cb64c15246291fdc0e27134b9cdce37 (diff) | |
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>
Diffstat (limited to 'arch/mips/include/asm/switch_to.h')
| -rw-r--r-- | arch/mips/include/asm/switch_to.h | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/arch/mips/include/asm/switch_to.h b/arch/mips/include/asm/switch_to.h index 278d45a09728..495c1041a2cc 100644 --- a/arch/mips/include/asm/switch_to.h +++ b/arch/mips/include/asm/switch_to.h @@ -16,22 +16,29 @@ #include <asm/watch.h> #include <asm/dsp.h> #include <asm/cop2.h> +#include <asm/msa.h> struct task_struct; +enum { + FP_SAVE_NONE = 0, + FP_SAVE_VECTOR = -1, + FP_SAVE_SCALAR = 1, +}; + /** * resume - resume execution of a task * @prev: The task previously executed. * @next: The task to begin executing. * @next_ti: task_thread_info(next). - * @usedfpu: Non-zero if prev's FP context should be saved. + * @fp_save: Which, if any, FP context to save for prev. * * This function is used whilst scheduling to save the context of prev & load * the context of next. Returns prev. */ extern asmlinkage struct task_struct *resume(struct task_struct *prev, struct task_struct *next, struct thread_info *next_ti, - u32 usedfpu); + s32 fp_save); extern unsigned int ll_bit; extern struct task_struct *ll_task; @@ -75,7 +82,8 @@ do { \ #define switch_to(prev, next, last) \ do { \ - u32 __usedfpu, __c0_stat; \ + u32 __c0_stat; \ + s32 __fpsave = FP_SAVE_NONE; \ __mips_mt_fpaff_switch_to(prev); \ if (cpu_has_dsp) \ __save_dsp(prev); \ @@ -88,8 +96,12 @@ do { \ write_c0_status(__c0_stat & ~ST0_CU2); \ } \ __clear_software_ll_bit(); \ - __usedfpu = test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU); \ - (last) = resume(prev, next, task_thread_info(next), __usedfpu); \ + if (test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU)) \ + __fpsave = FP_SAVE_SCALAR; \ + 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) \ |