kleidiai: Add runtime feature detection mechanism for aarch64/kleidiai (#26076)

* Add runtime feature detection mechanism for aarch64/kleidiai

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

* Address Review Comments

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

* Add log warning for NSMC reserved value

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

* Address review comments

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

* Fix Rebase, move code from cpu-feats to ggml-feats

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

* Address naming of runtime feature struct

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

---------

Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com>

ggml/src/ggml-cpu/arch/arm/cpu-feats.cpp

@@ -1,90 +1,11 @@
 #include "ggml-backend-impl.h"
+#include "ggml-feats.h"
 
-#if defined(__aarch64__)
+#if defined(__aarch64__) || defined(_M_ARM64)
-
-#if defined(__linux__)
-#include <sys/auxv.h>
-#elif defined(__APPLE__)
-#include <sys/sysctl.h>
-#endif
-
-#if !defined(HWCAP_FPHP)
-#define HWCAP_FPHP (1 << 9)
-#endif
-
-#if !defined(HWCAP_ASIMDHP)
-#define HWCAP_ASIMDHP (1 << 10)
-#endif
-
-#if !defined(HWCAP_ASIMDDP)
-#define HWCAP_ASIMDDP (1 << 20)
-#endif
-
-#if !defined(HWCAP_SVE)
-#define HWCAP_SVE (1 << 22)
-#endif
-
-#if !defined(HWCAP2_SVE2)
-#define HWCAP2_SVE2 (1 << 1)
-#endif
-
-#if !defined(HWCAP2_I8MM)
-#define HWCAP2_I8MM (1 << 13)
-#endif
-
-#if !defined(HWCAP2_SME)
-#define HWCAP2_SME (1 << 23)
-#endif
-
-struct aarch64_features {
-    // has_neon not needed, aarch64 has NEON guaranteed
-    bool has_dotprod     = false;
-    bool has_fp16        = false;
-    bool has_sve         = false;
-    bool has_sve2        = false;
-    bool has_i8mm        = false;
-    bool has_sme         = false;
-    bool has_sme2        = false;
-
-    aarch64_features() {
-#if defined(__linux__)
-        uint32_t hwcap = getauxval(AT_HWCAP);
-        uint32_t hwcap2 = getauxval(AT_HWCAP2);
-
-        has_dotprod = !!(hwcap & HWCAP_ASIMDDP);
-        has_fp16    = !!(hwcap & HWCAP_FPHP) && !!(hwcap & HWCAP_ASIMDHP);
-        has_sve     = !!(hwcap & HWCAP_SVE);
-        has_sve2    = !!(hwcap2 & HWCAP2_SVE2);
-        has_i8mm    = !!(hwcap2 & HWCAP2_I8MM);
-        has_sme     = !!(hwcap2 & HWCAP2_SME);
-#elif defined(__APPLE__)
-        int oldp = 0;
-        size_t size = sizeof(oldp);
-
-        if (sysctlbyname("hw.optional.arm.FEAT_DotProd", &oldp, &size, NULL, 0) == 0) {
-            has_dotprod = static_cast<bool>(oldp);
-        }
-
-        if (sysctlbyname("hw.optional.arm.FEAT_I8MM", &oldp, &size, NULL, 0) == 0) {
-            has_i8mm = static_cast<bool>(oldp);
-        }
-
-        if (sysctlbyname("hw.optional.arm.FEAT_SME", &oldp, &size, NULL, 0) == 0) {
-            has_sme = static_cast<bool>(oldp);
-        }
-
-        if (sysctlbyname("hw.optional.arm.FEAT_SME2", &oldp, &size, NULL, 0) == 0) {
-            has_sme2 = static_cast<bool>(oldp);
-        }
-
-        // Apple apparently does not implement SVE yet
-#endif
-    }
-};
 
 static int ggml_backend_cpu_aarch64_score() {
     int score = 1;
-    aarch64_features af;
+    ggml_feats_arch64_runtime_t af = ggml_get_aarch64_runtime_features();
 
 #ifdef GGML_USE_DOTPROD
     if (!af.has_dotprod) { return 0; }
@@ -116,4 +37,4 @@ static int ggml_backend_cpu_aarch64_score() {
 
 GGML_BACKEND_DL_SCORE_IMPL(ggml_backend_cpu_aarch64_score)
 
-# endif // defined(__aarch64__)
+# endif // defined(__aarch64__) || defined(_M_ARM64)

ggml/src/ggml-cpu/kleidiai/kleidiai.cpp

@@ -2,10 +2,12 @@
 // SPDX-License-Identifier: MIT
 //
 #include <arm_neon.h>
-#include <assert.h>
+#include <cassert>
-#include <stdio.h>
+#include <cstdio>
+#include <cstdlib>
 #include <atomic>
 #include <cfloat>
+#include <cctype>
 #include <algorithm>
 #include <cmath>
 #include <stdexcept>
@@ -17,25 +19,21 @@
 #include <cstddef>
 #include <cstdint>
 #include <fstream>
-#include <set>
+#include <map>
 #include <iostream>
 #include <climits>
+#include <charconv>
+#include <system_error>
 #if defined(__linux__)
 #include <asm/hwcap.h>
+#include <dirent.h>
 #include <sys/auxv.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#ifndef HWCAP2_SME2
-#define HWCAP2_SME2 (1UL << 37)
-#endif
 #elif defined(__APPLE__)
-#include <string_view>
 #include <sys/sysctl.h>
 #include <sys/types.h>
-#elif defined(_WIN32)
-#include <windows.h>
-#include <excpt.h>
 #endif
 
 #include "kleidiai.h"
@@ -43,6 +41,7 @@
 #include "ggml-cpu.h"
 #include "ggml-cpu-impl.h"
 #include "ggml-impl.h"
+#include "ggml-feats.h"
 #include "ggml-backend-impl.h"
 #include "ggml-threading.h"
 #include "traits.h"
@@ -64,8 +63,8 @@ struct ggml_kleidiai_context {
     ggml_kleidiai_kernels * kernels_q4;
     ggml_kleidiai_kernels * kernels_q8;
     ggml_kleidiai_kernels * kernels_f32;
-    int sme_thread_cap; // <= 0 means “SME disabled/unknown”;
+    int sme_thread_cap; // <= 0 means "SME disabled/unknown"
-    int thread_hint;    // <= 0 means “no hint”
+    int thread_hint;    // <= 0 means "no hint"
     int chunk_multiplier;
 } static ctx = { CPU_FEATURE_NONE, nullptr, nullptr, nullptr, 0, -1, 4 };
 
@@ -93,24 +92,117 @@ static const char* cpu_feature_to_string(cpu_feature f) {
     }
 }
 
+#if defined(__linux__) && defined(__aarch64__)
+static bool parse_cpu_dir_name(const char* name, size_t* cpu) {
+    if (strncmp(name, "cpu", 3) != 0 ||
+        name[3] < '0' || name[3] > '9') {
+        return false;
+    }
+
+    const char* first = name + 3;
+    const char* last = name + strlen(name);
+
+    size_t value = 0;
+    const auto [end, ec] = std::from_chars(first, last, value, 10);
+
+    if (ec != std::errc{} || end != last) {
+        return false;
+    }
+
+    *cpu = value;
+    return true;
+}
+
+static std::vector<size_t> detect_cpu_ids() {
+    std::vector<size_t> cpus;
+
+    DIR * dir = opendir("/sys/devices/system/cpu");
+    if (dir == nullptr) {
+        return cpus;
+    }
+
+    while (dirent * entry = readdir(dir)) {
+        size_t cpu = 0;
+        if (parse_cpu_dir_name(entry->d_name, &cpu)) {
+            cpus.push_back(cpu);
+        }
+    }
+    closedir(dir);
+
+    std::sort(cpus.begin(), cpus.end());
+    cpus.erase(std::unique(cpus.begin(), cpus.end()), cpus.end());
+    return cpus;
+}
+#endif
+
+#if defined(__APPLE__) && defined(__aarch64__)
+static bool apple_sme_counted_perf_level(std::string name) {
+    for (std::string::size_type i = 0; i < name.size(); ++i) {
+        name[i] = (char) std::tolower((unsigned char) name[i]);
+    }
+
+    // Conservative ceiling: only count perf-level names observed to provide full SME throughput.
+    // Future names should be calibrated here before they raise the automatic SME thread cap.
+    return name.find("super") != std::string::npos ||
+           name.find("performance") != std::string::npos;
+}
+#endif
+
+static void add_smcus_from_smidr(uint64_t smidr, size_t & num_private, std::map<uint32_t, size_t> & shared_counts) {
+    // Arm ARM: SMIDR_EL1. SH==0 is implementation-defined; keep the existing
+    // conservative policy and only treat zero affinity as private.
+    const uint32_t sh = (uint32_t)((smidr >> 13) & 0x3);
+    const uint32_t nsmc = (uint32_t)((smidr >> 56) & 0xF);
+    const size_t shared_count = nsmc == 0xF ? 1 : (size_t)nsmc + 1;
+    const uint32_t affinity = (uint32_t)(smidr & 0xFFFu);
+    const uint32_t affinity2 = (uint32_t)((smidr >> 32) & 0xFFFFFu);
+    const uint32_t id = (affinity2 << 12) | affinity;
+
+    if (nsmc == 0xF) {
+        GGML_LOG_WARN("kleidiai: NSMC detected as 0xF indicating reseved value, setting min safe shared SMCU count to 1");
+    }
+
+    switch (sh) {
+        case 2: // private SMCU
+            ++num_private;
+            break;
+        case 3: // shared SMCU
+            if (shared_counts[id] < shared_count) {
+                shared_counts[id] = shared_count;
+            }
+            break;
+        case 0:
+            if (id == 0) {
+                ++num_private;
+            } else if (shared_counts[id] < shared_count) {
+                shared_counts[id] = shared_count;
+            }
+            break;
+        default:
+            break;
+    }
+}
+
 static size_t detect_num_smcus() {
-    if (!ggml_cpu_has_sme()) {
+    auto runtime_feat = ggml_get_aarch64_runtime_features();
+    if (!runtime_feat.has_sme) {
         return 0;
     }
 
 #if defined(__linux__) && defined(__aarch64__)
     // Linux/aarch64: Best-effort count of Streaming Mode Compute Units (SMCUs) via SMIDR_EL1 sysfs.
     size_t num_private = 0;
-    std::set<uint32_t> shared_ids;
+    std::map<uint32_t, size_t> shared_counts;
 
-    for (size_t cpu = 0;; ++cpu) {
+    const std::vector<size_t> cpus = detect_cpu_ids();
+    for (const size_t cpu : cpus) {
         const std::string path =
             "/sys/devices/system/cpu/cpu" + std::to_string(cpu) +
             "/regs/identification/smidr_el1";
 
         std::ifstream file(path);
         if (!file.is_open()) {
-            break;
+            continue;
         }
 
         uint64_t smidr = 0;
@@ -118,54 +210,69 @@ static size_t detect_num_smcus() {
             continue;
         }
 
-        // Arm ARM: SMIDR_EL1
+        add_smcus_from_smidr(smidr, num_private, shared_counts);
-        const uint32_t sh = (uint32_t)((smidr >> 13) & 0x3);
-        // Build an "affinity-like" identifier for shared SMCUs.
-        // Keep the original packing logic, but isolate it here.
-        const uint32_t id = (uint32_t)((smidr & 0xFFFu) | ((smidr >> 20) & 0xFFFFF000u));
-
-        switch (sh) {
-            case 0b10: // private SMCU
-                ++num_private;
-                break;
-            case 0b11: // shared SMCU
-                shared_ids.emplace(id);
-                break;
-            case 0b00:
-                // Ambiguous / implementation-defined. Be conservative:
-                // treat id==0 as private, otherwise as shared.
-                if (id == 0) ++num_private;
-                else shared_ids.emplace(id);
-                break;
-            default:
-                break;
-        }
     }
 
-    return num_private + shared_ids.size();
+    size_t total = num_private;
+    for (const auto & entry : shared_counts) {
+        total += entry.second;
+    }
+    return total;
 
 #elif defined(__APPLE__) && defined(__aarch64__)
-    // table for known M4 variants. Users can override via GGML_KLEIDIAI_SME=<n>.
+    int perf_levels = 0;
-    char chip_name[256] = {};
+    size_t size = sizeof(perf_levels);
-    size_t size = sizeof(chip_name);
+    if (sysctlbyname("hw.nperflevels", &perf_levels, &size, nullptr, 0) != 0 ||
+        size != sizeof(perf_levels) || perf_levels <= 0) {
+        return 0;
+    }
 
-    if (sysctlbyname("machdep.cpu.brand_string", chip_name, &size, nullptr, 0) == 0) {
+    size_t units = 0;
-        const std::string brand(chip_name);
+    for (int i = 0; i < perf_levels; ++i) {
+        char key[64] = {};
+        int physical_cpus = 0;
+        int cpus_per_l2 = 0;
 
-        struct ModelSMCU { const char *match; size_t smcus; };
+        snprintf(key, sizeof(key), "hw.perflevel%d.physicalcpu", i);
-        static const ModelSMCU table[] = {
+        size = sizeof(physical_cpus);
-            { "M4 Ultra", 2 },
+        if (sysctlbyname(key, &physical_cpus, &size, nullptr, 0) != 0 ||
-            { "M4 Max",   2 },
+            size != sizeof(physical_cpus) || physical_cpus <= 0) {
-            { "M4 Pro",   2 },
+            continue;
-            { "M4",       1 },
+        }
-        };
 
-        for (const auto &e : table) {
+        snprintf(key, sizeof(key), "hw.perflevel%d.cpusperl2", i);
-            if (brand.find(e.match) != std::string::npos) {
+        size = sizeof(cpus_per_l2);
-                return e.smcus;
+        if (sysctlbyname(key, &cpus_per_l2, &size, nullptr, 0) != 0 ||
-            }
+            size != sizeof(cpus_per_l2) || cpus_per_l2 <= 0) {
+            continue;
+        }
+
+        snprintf(key, sizeof(key), "hw.perflevel%d.name", i);
+        size = 0;
+        if (sysctlbyname(key, nullptr, &size, nullptr, 0) != 0 || size == 0) {
+            continue;
+        }
+
+        std::string name(size, '\0');
+        if (sysctlbyname(key, &name[0], &size, nullptr, 0) != 0) {
+            continue;
+        }
+        name.resize(size);
+        while (!name.empty() && name.back() == '\0') {
+            name.pop_back();
+        }
+
+        if (apple_sme_counted_perf_level(name)) {
+            units += (size_t) ((physical_cpus + cpus_per_l2 - 1) / cpus_per_l2);
         }
     }
+
+    return units;
+
+#elif defined(_WIN32) && (defined(_M_ARM64) || defined(__aarch64__))
+    // No verified Windows arm64 SMCU detection path yet. Return unknown and use
+    // GGML_KLEIDIAI_SME=N as a diagnostics/debug override for SME thread cap
+    // calibration until a detection mechanism is verified on real hardware.
     return 0;
 
 #else
@@ -198,15 +305,18 @@ static void init_kleidiai_context(void) {
     if (!initialized) {
         initialized = true;
 
+        // Optional diagnostics/debug overrides; production defaults come from runtime detection.
         const char *env_sme         = getenv("GGML_KLEIDIAI_SME");
         const char *env_threads     = getenv("GGML_TOTAL_THREADS");
         const char *env_chunk_mult  = getenv("GGML_KLEIDIAI_CHUNK_MULTIPLIER");
 
+        auto runtime_feat = ggml_get_aarch64_runtime_features();
+
         size_t detected_smcus = 0;
 
-        ctx.features  = (ggml_cpu_has_dotprod()     ? CPU_FEATURE_DOTPROD : CPU_FEATURE_NONE) |
+        ctx.features  = (runtime_feat.has_dotprod  ? CPU_FEATURE_DOTPROD : CPU_FEATURE_NONE) |
-                        (ggml_cpu_has_matmul_int8() ? CPU_FEATURE_I8MM    : CPU_FEATURE_NONE) |
+                        (runtime_feat.has_i8mm     ? CPU_FEATURE_I8MM    : CPU_FEATURE_NONE) |
-                        ((ggml_cpu_has_sve() && ggml_cpu_get_sve_cnt() == QK8_0) ? CPU_FEATURE_SVE : CPU_FEATURE_NONE);
+                        (runtime_feat.sve_cnt == QK8_0 ? CPU_FEATURE_SVE : CPU_FEATURE_NONE);
 
         if (env_threads) {
             bool ok = false;
@@ -224,54 +334,54 @@ static void init_kleidiai_context(void) {
             }
         }
 
-        // SME policy:
-        // - env unset => auto-detect SMCUs; enable SME only if detected > 0.
-        // - env=0     => force off.
-        // - env>0     => force N cores, if the binary was built with SME.
         int sme_cores = 0;
         bool sme_env_ok = false;
         bool sme_env_set = (env_sme != nullptr);
 
+        const bool has_supported_sme_family = runtime_feat.has_sme;
+        bool sme_cap_detected = false;
+
+        if (has_supported_sme_family) {
+            detected_smcus = detect_num_smcus();
+            sme_cap_detected = detected_smcus > 0;
+            // Some platforms expose SME without exposing a calibrated SMCU count.
+            // Use one SME thread as the conservative default; add platform SMCU detection to raise it.
+            sme_cores = sme_cap_detected ? (int)detected_smcus : 1;
+
+            if (!sme_env_set && !sme_cap_detected) {
+                GGML_LOG_INFO("kleidiai: SME detected; SMCU count unavailable, using conservative SME thread cap=1\n");
+            }
+        }
+
+        // Runtime-detect SME support and available SMCUs first. The detected SMCU
+        // count is used as the SME thread cap, and GGML_KLEIDIAI_SME can debug-override that:
+        //   - unset: use runtime detection.
+        //   - 0:     disable SME-family kernels.
+        //   - N > 0: use N as the SME thread cap, if an SME-family kernel is selectable.
         if (sme_env_set) {
             bool ok = false;
             int v = parse_uint_env(env_sme, "GGML_KLEIDIAI_SME", &ok);
             sme_env_ok = ok;
 
-            if (!ok) {
+            if (ok) {
-                GGML_LOG_WARN("kleidiai: GGML_KLEIDIAI_SME set but parsing failed; falling back to runtime SME-core detection\n");
+                if (has_supported_sme_family) {
-                detected_smcus = detect_num_smcus();
+                    sme_cores = v;
-                sme_cores = detected_smcus > 0 ? (int)detected_smcus : 0;
+                } else {
-            } else if (v == 0) {
+                    if (v > 0) {
-                sme_cores = 0;
+                        GGML_LOG_WARN("kleidiai: GGML_KLEIDIAI_SME=%d but SME is not supported on this CPU; disabling SME-family kernels\n", v);
-            } else if (!ggml_cpu_has_sme()) {
+                    }
-                GGML_LOG_WARN("kleidiai: GGML_KLEIDIAI_SME=%d but the binary was not built with SME; disabling SME\n", v);
+                    sme_cores = 0;
-                sme_cores = 0;
+                }
             } else {
-                sme_cores = v;
+                GGML_LOG_WARN("kleidiai: GGML_KLEIDIAI_SME set but parsing failed; using automatic SME thread cap\n");
             }
-        } else {
-            detected_smcus = detect_num_smcus();
-            sme_cores = detected_smcus > 0 ? (int)detected_smcus : 0;
         }
 
-        if (!sme_env_set && ggml_cpu_has_sme() && sme_cores == 0) {
+        if (sme_cores > 0 && has_supported_sme_family) {
-            GGML_LOG_WARN("kleidiai: runtime SME-core detection returned 0; falling back to NEON\n");
-        }
-
-        if (sme_cores > 0) {
             ctx.features |= CPU_FEATURE_SME;
-#if defined(__aarch64__) && defined(__linux__)
+            if (runtime_feat.has_sme2) {
-            // ARM guarantees SME2 implies SME, so only check SME2 when SME is enabled.
-            if (getauxval(AT_HWCAP2) & HWCAP2_SME2) {
                 ctx.features |= CPU_FEATURE_SME2;
             }
-#elif defined(__aarch64__) && defined(__APPLE__)
-            int feat_sme2 = 0;
-            size_t size = sizeof(feat_sme2);
-            if (sysctlbyname("hw.optional.arm.FEAT_SME2", &feat_sme2, &size, NULL, 0) == 0 && feat_sme2) {
-                ctx.features |= CPU_FEATURE_SME2;
-            }
-#endif
         }
 
         // Kernel selection
@@ -297,16 +407,19 @@ static void init_kleidiai_context(void) {
             GGML_LOG_INFO("kleidiai: primary f32 kernel feature %s\n", cpu_feature_to_string(ctx.kernels_f32->required_cpu));
         }
 
-        ctx.sme_thread_cap = (ctx.features & CPU_FEATURE_SME) ? sme_cores : 0;
+        const bool has_selected_sme_family_kernel =
+            (ctx.kernels_q4  && is_sme_family(ctx.kernels_q4->required_cpu)) ||
+            (ctx.kernels_q8  && is_sme_family(ctx.kernels_q8->required_cpu)) ||
+            (ctx.kernels_f32 && is_sme_family(ctx.kernels_f32->required_cpu));
+        ctx.sme_thread_cap = has_selected_sme_family_kernel ? sme_cores : 0;
 
-        if (ctx.features & CPU_FEATURE_SME) {
+        if (has_selected_sme_family_kernel) {
-            const bool has_sme2 = (ctx.features & CPU_FEATURE_SME2) != CPU_FEATURE_NONE;
             if (sme_env_set && sme_env_ok && sme_cores > 0) {
-                GGML_LOG_INFO("kleidiai: SME%s enabled (GGML_KLEIDIAI_SME=%d override)\n",
+                GGML_LOG_INFO("kleidiai: SME enabled (GGML_KLEIDIAI_SME=%d debug override)\n", sme_cores);
-                    has_sme2 ? "2" : "", sme_cores);
+            } else if (sme_cap_detected) {
+                GGML_LOG_INFO("kleidiai: SME enabled (runtime-detected SME thread cap=%d)\n", sme_cores);
             } else {
-                GGML_LOG_INFO("kleidiai: SME%s enabled (runtime-detected SME cores=%d)\n",
+                GGML_LOG_INFO("kleidiai: SME enabled (runtime SME detected, conservative thread cap=%d)\n", sme_cores);
-                    has_sme2 ? "2" : "", sme_cores);
             }
         } else {
             GGML_LOG_INFO("kleidiai: SME disabled\n");
@@ -467,7 +580,7 @@ static int kleidiai_collect_kernel_chain_common(
     }
 
     if (is_sme_family(primary->required_cpu)) {
-        const cpu_feature fallback_mask = static_cast<cpu_feature>(features & ~CPU_FEATURE_SME & ~CPU_FEATURE_SME2);
+        const cpu_feature fallback_mask = static_cast<cpu_feature>(features & ~(CPU_FEATURE_SME | CPU_FEATURE_SME2));
         if (fallback_mask != CPU_FEATURE_NONE) {
             ggml_kleidiai_kernels * fallback = select_fallback(fallback_mask);
             if (fallback && fallback != primary &&
@@ -1077,13 +1190,14 @@ class tensor_traits : public ggml::cpu::tensor_traits {
         const int ith_total = params->ith;
 
         int sme_slot = -1;
+        int non_sme_slot = -1;
         for (int i = 0; i < runtime_count; ++i) {
             if (is_sme_family(runtime[i].kernels->required_cpu)) {
                 sme_slot = i;
                 break;
             }
         }
-        int non_sme_slot = -1;
+
         for (int i = 0; i < runtime_count; ++i) {
             if (!is_sme_family(runtime[i].kernels->required_cpu)) {
                 non_sme_slot = i;

ggml/src/ggml-feats.h

@@ -0,0 +1,166 @@
+#pragma once
+
+#if defined(__aarch64__) || defined(_M_ARM64)
+
+#if defined(__linux__)
+#include <sys/auxv.h>
+#include <sys/prctl.h>
+
+#if !defined(HWCAP2_SVE2)
+#define HWCAP2_SVE2 (1ULL << 1)
+#endif
+
+#if !defined(HWCAP_FPHP)
+#define HWCAP_FPHP (1 << 9)
+#endif
+
+#if !defined(HWCAP_ASIMDHP)
+#define HWCAP_ASIMDHP (1 << 10)
+#endif
+
+#if !defined(HWCAP2_I8MM)
+#define HWCAP2_I8MM (1ULL << 13)
+#endif
+
+#if !defined(HWCAP_ASIMDDP)
+#define HWCAP_ASIMDDP (1 << 20)
+#endif
+
+#if !defined(HWCAP_SVE)
+#define HWCAP_SVE (1 << 22)
+#endif
+
+#if !defined(HWCAP2_SME)
+#define HWCAP2_SME (1ULL << 23)
+#endif
+
+#if !defined(HWCAP2_SME2)
+#define HWCAP2_SME2 (1ULL << 37)
+#endif
+
+#if !defined(PR_SVE_GET_VL)
+#define PR_SVE_GET_VL 51
+#endif
+
+#if !defined(PR_SVE_VL_LEN_MASK)
+#define PR_SVE_VL_LEN_MASK 0xffff
+#endif
+
+#elif defined(__APPLE__)
+#include <sys/sysctl.h>
+#elif defined(_WIN32)
+#include <windows.h>
+
+#if !defined(PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE 43
+#endif
+
+#if !defined(PF_ARM_SVE_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_SVE_INSTRUCTIONS_AVAILABLE 46
+#endif
+
+#if !defined(PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE 47
+#endif
+
+#if !defined(PF_ARM_V82_I8MM_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_V82_I8MM_INSTRUCTIONS_AVAILABLE 66
+#endif
+
+#if !defined(PF_ARM_V82_FP16_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_V82_FP16_INSTRUCTIONS_AVAILABLE 67
+#endif
+
+#if !defined(PF_ARM_SME_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_SME_INSTRUCTIONS_AVAILABLE 70
+#endif
+
+#if !defined(PF_ARM_SME2_INSTRUCTIONS_AVAILABLE)
+#define PF_ARM_SME2_INSTRUCTIONS_AVAILABLE 71
+#endif
+
+#endif
+
+typedef struct ggml_feats_arch64_runtime {
+    bool has_dotprod;
+    bool has_fp16;
+    bool has_sve;
+    bool has_sve2;
+    bool has_i8mm;
+    bool has_sme;
+    bool has_sme2;
+    int sve_cnt;
+} ggml_feats_arch64_runtime_t;
+
+static inline ggml_feats_arch64_runtime_t ggml_get_aarch64_runtime_features(void) {
+    ggml_feats_arch64_runtime_t runtime_feat = {};
+
+#if defined(__linux__)
+    const unsigned long hwcap  = getauxval(AT_HWCAP);
+    const unsigned long hwcap2 = getauxval(AT_HWCAP2);
+
+    runtime_feat.has_dotprod = !!(hwcap & HWCAP_ASIMDDP);
+    runtime_feat.has_fp16    = !!(hwcap & HWCAP_FPHP) && !!(hwcap & HWCAP_ASIMDHP);;
+    runtime_feat.has_sve     = !!(hwcap & HWCAP_SVE);
+    runtime_feat.has_sve2    = !!(hwcap2 & HWCAP2_SVE2);
+    runtime_feat.has_i8mm    = !!(hwcap2 & HWCAP2_I8MM);
+    runtime_feat.has_sme     = !!(hwcap2 & HWCAP2_SME);
+    runtime_feat.has_sme2    = !!(hwcap2 & HWCAP2_SME2);
+
+    if (runtime_feat.has_sve) {
+        const int vl = prctl(PR_SVE_GET_VL);
+        if (vl >= 0) {
+            runtime_feat.sve_cnt = vl & PR_SVE_VL_LEN_MASK;
+        }
+    }
+#elif defined(__APPLE__)
+    int oldp = 0;
+    size_t size = sizeof(oldp);
+
+    if (sysctlbyname("hw.optional.arm.FEAT_DotProd", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_dotprod = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_FP16", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_fp16 = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_SVE", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_sve = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_SVE2", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_sve2 = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_I8MM", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_i8mm = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_SME", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_sme = static_cast<bool>(oldp);
+    }
+
+    if (sysctlbyname("hw.optional.arm.FEAT_SME2", &oldp, &size, nullptr, 0) == 0) {
+        runtime_feat.has_sme2 = static_cast<bool>(oldp);
+    }
+
+    // Apple does not support userspace non-streaming SVE; keep SVE vector length unknown.
+    runtime_feat.sve_cnt = 0;
+#elif defined (_WIN32)
+    runtime_feat.has_dotprod = IsProcessorFeaturePresent(PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_fp16    = IsProcessorFeaturePresent(PF_ARM_V82_FP16_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_sve     = IsProcessorFeaturePresent(PF_ARM_SVE_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_sve2    = IsProcessorFeaturePresent(PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_i8mm    = IsProcessorFeaturePresent(PF_ARM_V82_I8MM_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_sme     = IsProcessorFeaturePresent(PF_ARM_SME_INSTRUCTIONS_AVAILABLE) != 0;
+    runtime_feat.has_sme2    = IsProcessorFeaturePresent(PF_ARM_SME2_INSTRUCTIONS_AVAILABLE) != 0;
+
+    // Windows exposes SVE feature presence, but not the runtime SVE vector length here.
+    runtime_feat.sve_cnt = 0;
+#endif
+
+    return runtime_feat;
+}
+
+#endif // defined(__aarch64__) || defined(_M_ARM64)