1 files changed, 121 insertions, 2 deletions

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index e4fba0bfb55e..5e5fbd9cba75 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -136,6 +136,12 @@ __ro_after_init struct vl_info vl_info[ARM64_VEC_MAX] = {
 		.max_virtualisable_vl	= SVE_VL_MIN,
 	},
 #endif
+#ifdef CONFIG_ARM64_SME
+	[ARM64_VEC_SME] = {
+		.type			= ARM64_VEC_SME,
+		.name			= "SME",
+	},
+#endif
 };
 
 static unsigned int vec_vl_inherit_flag(enum vec_type type)
@@ -186,6 +192,20 @@ extern void __percpu *efi_sve_state;
 
 #endif /* ! CONFIG_ARM64_SVE */
 
+#ifdef CONFIG_ARM64_SME
+
+static int get_sme_default_vl(void)
+{
+	return get_default_vl(ARM64_VEC_SME);
+}
+
+static void set_sme_default_vl(int val)
+{
+	set_default_vl(ARM64_VEC_SME, val);
+}
+
+#endif
+
 DEFINE_PER_CPU(bool, fpsimd_context_busy);
 EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy);
 
@@ -409,6 +429,8 @@ static unsigned int find_supported_vector_length(enum vec_type type,
 
 	if (vl > max_vl)
 		vl = max_vl;
+	if (vl < info->min_vl)
+		vl = info->min_vl;
 
 	bit = find_next_bit(info->vq_map, SVE_VQ_MAX,
 			    __vq_to_bit(sve_vq_from_vl(vl)));
@@ -770,7 +792,23 @@ static void vec_probe_vqs(struct vl_info *info,
 
 	for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) {
 		write_vl(info->type, vq - 1); /* self-syncing */
-		vl = sve_get_vl();
+
+		switch (info->type) {
+		case ARM64_VEC_SVE:
+			vl = sve_get_vl();
+			break;
+		case ARM64_VEC_SME:
+			vl = sme_get_vl();
+			break;
+		default:
+			vl = 0;
+			break;
+		}
+
+		/* Minimum VL identified? */
+		if (sve_vq_from_vl(vl) > vq)
+			break;
+
 		vq = sve_vq_from_vl(vl); /* skip intervening lengths */
 		set_bit(__vq_to_bit(vq), map);
 	}
@@ -1017,7 +1055,88 @@ void fa64_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
 		       SYS_SMCR_EL1);
 }
 
-#endif /* CONFIG_ARM64_SVE */
+/*
+ * Read the pseudo-SMCR used by cpufeatures to identify the supported
+ * vector length.
+ *
+ * Use only if SME is present.
+ * This function clobbers the SME vector length.
+ */
+u64 read_smcr_features(void)
+{
+	u64 smcr;
+	unsigned int vq_max;
+
+	sme_kernel_enable(NULL);
+	sme_smstart_sm();
+
+	/*
+	 * Set the maximum possible VL.
+	 */
+	write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_LEN_MASK,
+		       SYS_SMCR_EL1);
+
+	smcr = read_sysreg_s(SYS_SMCR_EL1);
+	smcr &= ~(u64)SMCR_ELx_LEN_MASK; /* Only the LEN field */
+	vq_max = sve_vq_from_vl(sve_get_vl());
+	smcr |= vq_max - 1; /* set LEN field to maximum effective value */
+
+	sme_smstop_sm();
+
+	return smcr;
+}
+
+void __init sme_setup(void)
+{
+	struct vl_info *info = &vl_info[ARM64_VEC_SME];
+	u64 smcr;
+	int min_bit;
+
+	if (!system_supports_sme())
+		return;
+
+	/*
+	 * SME doesn't require any particular vector length be
+	 * supported but it does require at least one.  We should have
+	 * disabled the feature entirely while bringing up CPUs but
+	 * let's double check here.
+	 */
+	WARN_ON(bitmap_empty(info->vq_map, SVE_VQ_MAX));
+
+	min_bit = find_last_bit(info->vq_map, SVE_VQ_MAX);
+	info->min_vl = sve_vl_from_vq(__bit_to_vq(min_bit));
+
+	smcr = read_sanitised_ftr_reg(SYS_SMCR_EL1);
+	info->max_vl = sve_vl_from_vq((smcr & SMCR_ELx_LEN_MASK) + 1);
+
+	/*
+	 * Sanity-check that the max VL we determined through CPU features
+	 * corresponds properly to sme_vq_map.  If not, do our best:
+	 */
+	if (WARN_ON(info->max_vl != find_supported_vector_length(ARM64_VEC_SME,
+								 info->max_vl)))
+		info->max_vl = find_supported_vector_length(ARM64_VEC_SME,
+							    info->max_vl);
+
+	WARN_ON(info->min_vl > info->max_vl);
+
+	/*
+	 * For the default VL, pick the maximum supported value <= 32
+	 * (256 bits) if there is one since this is guaranteed not to
+	 * grow the signal frame when in streaming mode, otherwise the
+	 * minimum available VL will be used.
+	 */
+	set_sme_default_vl(find_supported_vector_length(ARM64_VEC_SME, 32));
+
+	pr_info("SME: minimum available vector length %u bytes per vector\n",
+		info->min_vl);
+	pr_info("SME: maximum available vector length %u bytes per vector\n",
+		info->max_vl);
+	pr_info("SME: default vector length %u bytes per vector\n",
+		get_sme_default_vl());
+}
+
+#endif /* CONFIG_ARM64_SME */
 
 /*
  * Trapped SVE access