[PATCH v4 6/8] arm64/sve: Implement a helper to load SVE registers from FPSIMD state

Mark Brown broonie at kernel.org
Fri Aug 28 14:11:53 EDT 2020


From: Julien Grall <julien.grall at arm.com>

In a follow-up patch, we may save the FPSIMD rather than the full SVE
state when the state has to be zeroed on return to userspace (e.g
during a syscall).

Introduce an helper to load SVE vectors from FPSIMD state and zero the rest
of SVE registers.

Signed-off-by: Julien Grall <julien.grall at arm.com>
Reviewed-by: Dave Martin <Dave.Martin at arm.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 arch/arm64/include/asm/fpsimd.h  |  2 ++
 arch/arm64/kernel/entry-fpsimd.S | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 958f642e930d..bec5f14b622a 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -70,6 +70,8 @@ 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_load_from_fpsimd_state(struct user_fpsimd_state const *state,
+				       unsigned long vq_minus_1);
 extern unsigned int sve_get_vl(void);
 
 struct arm64_cpu_capabilities;
diff --git a/arch/arm64/kernel/entry-fpsimd.S b/arch/arm64/kernel/entry-fpsimd.S
index fdf7a5a35c63..2ca395c25448 100644
--- a/arch/arm64/kernel/entry-fpsimd.S
+++ b/arch/arm64/kernel/entry-fpsimd.S
@@ -48,6 +48,23 @@ SYM_FUNC_START(sve_get_vl)
 	ret
 SYM_FUNC_END(sve_get_vl)
 
+/*
+ * Load SVE state from FPSIMD state.
+ *
+ * x0 = pointer to struct fpsimd_state
+ * x1 = VQ - 1
+ *
+ * Each SVE vector will be loaded with the first 128-bits taken from FPSIMD
+ * and the rest zeroed. All the other SVE registers will be zeroed.
+ */
+SYM_FUNC_START(sve_load_from_fpsimd_state)
+		sve_load_vq	x1, x2, x3
+		fpsimd_restore	x0, 8
+ _for n, 0, 15, _sve_pfalse	\n
+		_sve_wrffr	0
+		ret
+SYM_FUNC_END(sve_load_from_fpsimd_state)
+
 /* Zero all SVE registers but the first 128-bits of each vector */
 SYM_FUNC_START(sve_flush_live)
 	sve_flush
-- 
2.20.1




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