[PATCH v1 3/3] arm64/sve: Skip flushing Z registers with 128 bit vectors
flat view
STALE1977d
From: Mark Brown <broonie@kernel.org>
Date: 2021-05-10 12:26:29
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
When the SVE vector length is 128 bits then there are no bits in the Z registers which are not shared with the V registers so we can skip them when zeroing state not shared with FPSIMD, this results in a minor performance improvement. Signed-off-by: Mark Brown <broonie@kernel.org> --- arch/arm64/include/asm/fpsimd.h | 2 +- arch/arm64/kernel/entry-fpsimd.S | 9 +++++++-- arch/arm64/kernel/fpsimd.c | 6 ++++-- 3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 2599504674b5..c072161d5c65 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h@@ -69,7 +69,7 @@ static inline void *sve_pffr(struct thread_struct *thread) extern void sve_save_state(void *state, u32 *pfpsr); extern void sve_load_state(void const *state, u32 const *pfpsr, unsigned long vq_minus_1); -extern void sve_flush_live(void); +extern void sve_flush_live(unsigned long vq_minus_1); extern void sve_load_from_fpsimd_state(struct user_fpsimd_state const *state, unsigned long vq_minus_1); extern unsigned int sve_get_vl(void);
diff --git a/arch/arm64/kernel/entry-fpsimd.S b/arch/arm64/kernel/entry-fpsimd.S
index ee8773f4088b..090449e825e7 100644
--- a/arch/arm64/kernel/entry-fpsimd.S
+++ b/arch/arm64/kernel/entry-fpsimd.S@@ -70,10 +70,15 @@ SYM_FUNC_START(sve_load_from_fpsimd_state) ret SYM_FUNC_END(sve_load_from_fpsimd_state) -/* Zero all SVE registers but the first 128-bits of each vector */ +/* + * Zero all SVE registers but the first 128-bits of each vector + * + * x0 = VQ - 1 + */ SYM_FUNC_START(sve_flush_live) + cbz x0, 1f // A VQ-1 of 0 is 128 bits so no extra Z state sve_flush_z - sve_flush_p +1: sve_flush_p sve_flush_ffr ret SYM_FUNC_END(sve_flush_live)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index ad3dd34a83cf..e57b23f95284 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c@@ -957,8 +957,10 @@ void do_sve_acc(unsigned int esr, struct pt_regs *regs) * disabling the trap, otherwise update our in-memory copy. */ if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { - sve_set_vq(sve_vq_from_vl(current->thread.sve_vl) - 1); - sve_flush_live(); + unsigned long vq_minus_one = + sve_vq_from_vl(current->thread.sve_vl) - 1; + sve_set_vq(vq_minus_one); + sve_flush_live(vq_minus_one); fpsimd_bind_task_to_cpu(); } else { fpsimd_to_sve(current);
--
2.20.1
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel