[PATCH v13 05/32] arm64/sve: Factor virtualizable VL discovery out of SVE specific code

[Mark Brown <broonie@kernel.org>]

In preparation for reuising it for SME pull the code for discovering the
maximum virtualizable vector length out of sve_setup() into a separate
function, updating to return 0 without a WARN_ON() for the case where no
virtualisable VL exists.  For SVE this case is architecturally invalid
but for SME it is valid if ill advised.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index b5535f8c9bd9..314f5d61be11 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1118,6 +1118,29 @@ int vec_verify_vq_map(enum vec_type type)
 	return 0;
 }
 
+static int __init vec_virtualisable_vl(struct vl_info *info)
+{
+	DECLARE_BITMAP(partial_only_map, SVE_VQ_MAX);
+	unsigned long b_min_partial, b_max_virt;
+
+	bitmap_andnot(partial_only_map, info->vq_partial_map, info->vq_map,
+		      SVE_VQ_MAX);
+	b_min_partial = find_last_bit(partial_only_map, SVE_VQ_MAX);
+
+	/* All implemented VLs are virtualisable */
+	if (b_min_partial >= SVE_VQ_MAX)
+		return info->max_vl;
+
+	b_max_virt = find_next_bit(info->vq_map, SVE_VQ_MAX, b_min_partial);
+
+	/* No implemented VLs are virtualisable */
+	if (b_max_virt >= SVE_VQ_MAX)
+		return 0;
+
+	/* At least one virtualisable VL exists */
+	return sve_vl_from_vq(__bit_to_vq(b_max_virt));
+}
+
 void cpu_enable_sve(const struct arm64_cpu_capabilities *__always_unused p)
 {
 	write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_ZEN_EL1EN, CPACR_EL1);
@@ -1129,8 +1152,6 @@ void cpu_enable_sve(const struct arm64_cpu_capabilities *__always_unused p)
 void __init sve_setup(void)
 {
 	struct vl_info *info = &vl_info[ARM64_VEC_SVE];
-	DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
-	unsigned long b;
 	int max_bit;
 
 	if (!system_supports_sve())
@@ -1153,21 +1174,7 @@ void __init sve_setup(void)
 	 */
 	set_sve_default_vl(find_supported_vector_length(ARM64_VEC_SVE, 64));
 
-	bitmap_andnot(tmp_map, info->vq_partial_map, info->vq_map,
-		      SVE_VQ_MAX);
-
-	b = find_last_bit(tmp_map, SVE_VQ_MAX);
-	if (b >= SVE_VQ_MAX)
-		/* No non-virtualisable VLs found */
-		info->max_virtualisable_vl = SVE_VQ_MAX;
-	else if (WARN_ON(b == SVE_VQ_MAX - 1))
-		/* No virtualisable VLs?  This is architecturally forbidden. */
-		info->max_virtualisable_vl = SVE_VQ_MIN;
-	else /* b + 1 < SVE_VQ_MAX */
-		info->max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1));
-
-	if (info->max_virtualisable_vl > info->max_vl)
-		info->max_virtualisable_vl = info->max_vl;
+	info->max_virtualisable_vl = vec_virtualisable_vl(info);
 
 	pr_info("%s: maximum available vector length %u bytes per vector\n",
 		info->name, info->max_vl);

-- 
2.47.3