[9.0] Fix vec_caps to test for OS support too (on x64) (#126911)

docs/changelog/126911.yaml

@@ -0,0 +1,6 @@
+pr: 126911
+summary: Fix `vec_caps` to test for OS support too (on x64)
+area: Vector Search
+type: bug
+issues:
+ - 126809

libs/native/libraries/build.gradle

@@ -19,7 +19,7 @@ configurations {
 }
 
 var zstdVersion = "1.5.5"
-var vecVersion = "1.0.10"
+var vecVersion = "1.0.11"
 
 repositories {
   exclusiveContent {

libs/native/src/main/java/org/elasticsearch/nativeaccess/jdk/JdkVectorLibrary.java

@@ -41,7 +41,7 @@ public final class JdkVectorLibrary implements VectorLibrary {
         try {
             int caps = (int) vecCaps$mh.invokeExact();
             logger.info("vec_caps=" + caps);
-            if (caps != 0) {
+            if (caps > 0) {
                 if (caps == 2) {
                     dot7u$mh = downcallHandle(
                         "dot7u_2",
@@ -67,6 +67,11 @@ public final class JdkVectorLibrary implements VectorLibrary {
                 }
                 INSTANCE = new JdkVectorSimilarityFunctions();
             } else {
+                if (caps < 0) {
+                    logger.warn("""
+                        Your CPU supports vector capabilities, but they are disabled at OS level. For optimal performance, \
+                        enable them in your OS/Hypervisor/VM/container""");
+                }
                 dot7u$mh = null;
                 sqr7u$mh = null;
                 INSTANCE = null;

libs/simdvec/native/build.gradle

@@ -11,7 +11,7 @@ apply plugin: 'cpp'
 
 var os = org.gradle.internal.os.OperatingSystem.current()
 
-// To update this library run publish_vec_binaries.sh  ( or ./gradlew vecSharedLibrary )
+// To update this library run publish_vec_binaries.sh  ( or ./gradlew buildSharedLibrary )
 // Or
 // For local development, build the docker image with:
 //   docker build --platform linux/arm64 --progress=plain --file=Dockerfile.aarch64 . (for aarch64)

libs/simdvec/native/publish_vec_binaries.sh

@@ -20,7 +20,7 @@ if [ -z "$ARTIFACTORY_API_KEY" ]; then
   exit 1;
 fi
 
-VERSION="1.0.10"
+VERSION="1.0.11"
 ARTIFACTORY_REPOSITORY="${ARTIFACTORY_REPOSITORY:-https://artifactory.elastic.dev/artifactory/elasticsearch-native/}"
 TEMP=$(mktemp -d)
 

libs/simdvec/native/src/vec/c/amd64/vec.c

@@ -46,6 +46,23 @@ static inline void cpuid(int output[4], int functionNumber) {
 #endif
 }
 
+// Multi-platform XGETBV "intrinsic"
+static inline int64_t xgetbv(int ctr) {
+#if defined(__GNUC__) || defined(__clang__)
+    // use inline assembly, Gnu/AT&T syntax
+    uint32_t a, d;
+    __asm("xgetbv" : "=a"(a),"=d"(d) : "c"(ctr) : );
+    return a | (((uint64_t) d) << 32);
+
+#elif (defined (_MSC_FULL_VER) && _MSC_FULL_VER >= 160040000) || (defined (__INTEL_COMPILER) && __INTEL_COMPILER >= 1200)
+    // Microsoft or Intel compiler supporting _xgetbv intrinsic
+    return _xgetbv(ctr);
+
+#else
+   #error Unsupported compiler
+#endif
+}
+
 // Utility function to horizontally add 8 32-bit integers
 static inline int hsum_i32_8(const __m256i a) {
     const __m128i sum128 = _mm_add_epi32(_mm256_castsi256_si128(a), _mm256_extractf128_si256(a, 1));
@@ -57,11 +74,20 @@ static inline int hsum_i32_8(const __m256i a) {
 
 EXPORT int vec_caps() {
     int cpuInfo[4] = {-1};
-    // Calling __cpuid with 0x0 as the function_id argument
+    // Calling CPUID function 0x0 as the function_id argument
     // gets the number of the highest valid function ID.
     cpuid(cpuInfo, 0);
     int functionIds = cpuInfo[0];
+    if (functionIds == 0) {
+        // No CPUID functions
+        return 0;
+    }
+    // call CPUID function 0x1 for feature flags
+    cpuid(cpuInfo, 1);
+    int hasOsXsave = (cpuInfo[2] & (1 << 27)) != 0;
+    int avxEnabledInOS = hasOsXsave && ((xgetbv(0) & 6) == 6);
     if (functionIds >= 7) {
+        // call CPUID function 0x7 for AVX2/512 flags
         cpuid(cpuInfo, 7);
         int ebx = cpuInfo[1];
         int ecx = cpuInfo[2];
@@ -72,10 +98,18 @@ EXPORT int vec_caps() {
         // int avx512_vnni = (ecx & 0x00000800) != 0;
         // if (avx512 && avx512_vnni) {
         if (avx512) {
-            return 2;
+            if (avxEnabledInOS) {
+                return 2;
+            } else {
+                return -2;
+            }
         }
         if (avx2) {
-            return 1;
+            if (avxEnabledInOS) {
+                return 1;
+            } else {
+                return -1;
+            }
         }
     }
     return 0;