arm64/sve: Factor out FPSIMD to SVE state conversion

Currently we convert from FPSIMD to SVE register state in memory in
two places.

To ease future maintenance, let's consolidate this in one place.
Reviewed-by: Julien Grall <julien.grall@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/fpsimd.c

@@ -406,6 +406,18 @@ static __uint128_t arm64_cpu_to_le128(__uint128_t x)
 
 #define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x)
 
+static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst,
+			    unsigned int vq)
+{
+	unsigned int i;
+	__uint128_t *p;
+
+	for (i = 0; i < 32; ++i) {
+		p = (__uint128_t *)ZREG(sst, vq, i);
+		*p = arm64_cpu_to_le128(fst->vregs[i]);
+	}
+}
+
 /*
  * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to
  * task->thread.sve_state.
@@ -423,17 +435,12 @@ static void fpsimd_to_sve(struct task_struct *task)
 	unsigned int vq;
 	void *sst = task->thread.sve_state;
 	struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;
-	unsigned int i;
-	__uint128_t *p;
 
 	if (!system_supports_sve())
 		return;
 
 	vq = sve_vq_from_vl(task->thread.sve_vl);
-	for (i = 0; i < 32; ++i) {
-		p = (__uint128_t *)ZREG(sst, vq, i);
-		*p = arm64_cpu_to_le128(fst->vregs[i]);
-	}
+	__fpsimd_to_sve(sst, fst, vq);
 }
 
 /*
@@ -550,8 +557,6 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
 	unsigned int vq;
 	void *sst = task->thread.sve_state;
 	struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;
-	unsigned int i;
-	__uint128_t *p;
 
 	if (!test_tsk_thread_flag(task, TIF_SVE))
 		return;
@@ -559,11 +564,7 @@ void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
 	vq = sve_vq_from_vl(task->thread.sve_vl);
 
 	memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
-
-	for (i = 0; i < 32; ++i) {
-		p = (__uint128_t *)ZREG(sst, vq, i);
-		*p = arm64_cpu_to_le128(fst->vregs[i]);
-	}
+	__fpsimd_to_sve(sst, fst, vq);
 }
 
 int sve_set_vector_length(struct task_struct *task,