libx86: Introduce x86_cpuid_lookup_vendor()

Also introduce constants for the vendor strings in CPUID leaf 0.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

tools/tests/cpu-policy/test-cpu-policy.c

@@ -8,6 +8,7 @@
 #include <err.h>
 
 #include <xen-tools/libs.h>
+#include <xen/asm/x86-vendors.h>
 #include <xen/lib/x86/cpuid.h>
 #include <xen/lib/x86/msr.h>
 #include <xen/domctl.h>
@@ -19,6 +20,40 @@ static unsigned int nr_failures;
     printf(fmt, ##__VA_ARGS__);                 \
 })
 
+static void test_vendor_identification(void)
+{
+    static const struct test {
+        union {
+            char ident[12];
+            struct {
+                uint32_t b, d, c;
+            };
+        };
+        unsigned int vendor;
+    } tests[] = {
+        { { "GenuineIntel" }, X86_VENDOR_INTEL },
+        { { "AuthenticAMD" }, X86_VENDOR_AMD },
+        { { "CentaurHauls" }, X86_VENDOR_CENTAUR },
+        { { "  Shanghai  " }, X86_VENDOR_SHANGHAI },
+
+        { { ""             }, X86_VENDOR_UNKNOWN },
+        { { "            " }, X86_VENDOR_UNKNOWN },
+        { { "xxxxxxxxxxxx" }, X86_VENDOR_UNKNOWN },
+    };
+
+    printf("Testing CPU vendor identification:\n");
+
+    for ( size_t i = 0; i < ARRAY_SIZE(tests); ++i )
+    {
+        const struct test *t = &tests[i];
+        unsigned int vendor = x86_cpuid_lookup_vendor(t->b, t->c, t->d);
+
+        if ( vendor != t->vendor )
+            fail("  Test '%.12s', expected vendor %u, got %u\n",
+                 t->ident, t->vendor, vendor);
+    }
+}
+
 static void test_cpuid_serialise_success(void)
 {
     static const struct test {
@@ -243,6 +278,8 @@ int main(int argc, char **argv)
 {
     printf("CPU Policy unit tests\n");
 
+    test_vendor_identification();
+
     test_cpuid_serialise_success();
     test_msr_serialise_success();
 

xen/include/asm-x86/x86-vendors.h

@@ -3,12 +3,33 @@
 
 /*
  * CPU vendor IDs
+ *
+ * - X86_VENDOR_* are Xen-internal identifiers.  Values and order are
+ *   arbitrary.
+ * - X86_VENDOR_*_E?X are architectural information from CPUID leaf 0
  */
 #define X86_VENDOR_UNKNOWN 0
+
 #define X86_VENDOR_INTEL 1
+#define X86_VENDOR_INTEL_EBX 0x756e6547U /* "GenuineIntel" */
+#define X86_VENDOR_INTEL_ECX 0x6c65746eU
+#define X86_VENDOR_INTEL_EDX 0x49656e69U
+
 #define X86_VENDOR_AMD 2
+#define X86_VENDOR_AMD_EBX 0x68747541U /* "AuthenticAMD" */
+#define X86_VENDOR_AMD_ECX 0x444d4163U
+#define X86_VENDOR_AMD_EDX 0x69746e65U
+
 #define X86_VENDOR_CENTAUR 3
+#define X86_VENDOR_CENTAUR_EBX 0x746e6543U /* "CentaurHauls" */
+#define X86_VENDOR_CENTAUR_ECX 0x736c7561U
+#define X86_VENDOR_CENTAUR_EDX 0x48727561U
+
 #define X86_VENDOR_SHANGHAI 4
+#define X86_VENDOR_SHANGHAI_EBX 0x68532020U /* "  Shanghai  " */
+#define X86_VENDOR_SHANGHAI_ECX 0x20206961U
+#define X86_VENDOR_SHANGHAI_EDX 0x68676e61U
+
 #define X86_VENDOR_NUM 5
 
 #endif	/* __XEN_X86_VENDORS_H__ */

xen/include/xen/lib/x86/cpuid.h

@@ -65,6 +65,12 @@ static inline void cpuid_count_leaf(
 #undef BX_CON
 #undef XCHG
 
+/**
+ * Given the vendor id from CPUID leaf 0, look up Xen's internal integer
+ * vendor ID.  Returns X86_VENDOR_UNKNOWN for any unknown vendor.
+ */
+unsigned int x86_cpuid_lookup_vendor(uint32_t ebx, uint32_t ecx, uint32_t edx);
+
 #define CPUID_GUEST_NR_BASIC      (0xdu + 1)
 #define CPUID_GUEST_NR_CACHE      (5u + 1)
 #define CPUID_GUEST_NR_FEAT       (0u + 1)

xen/lib/x86/cpuid.c

@@ -2,6 +2,38 @@
 
 #include <xen/lib/x86/cpuid.h>
 
+unsigned int x86_cpuid_lookup_vendor(uint32_t ebx, uint32_t ecx, uint32_t edx)
+{
+    switch ( ebx )
+    {
+    case X86_VENDOR_INTEL_EBX:
+        if ( ecx == X86_VENDOR_INTEL_ECX &&
+             edx == X86_VENDOR_INTEL_EDX )
+            return X86_VENDOR_INTEL;
+        break;
+
+    case X86_VENDOR_AMD_EBX:
+        if ( ecx == X86_VENDOR_AMD_ECX &&
+             edx == X86_VENDOR_AMD_EDX )
+            return X86_VENDOR_AMD;
+        break;
+
+    case X86_VENDOR_CENTAUR_EBX:
+        if ( ecx == X86_VENDOR_CENTAUR_ECX &&
+             edx == X86_VENDOR_CENTAUR_EDX )
+            return X86_VENDOR_CENTAUR;
+        break;
+
+    case X86_VENDOR_SHANGHAI_EBX:
+        if ( ecx == X86_VENDOR_SHANGHAI_ECX &&
+             edx == X86_VENDOR_SHANGHAI_EDX )
+            return X86_VENDOR_SHANGHAI;
+        break;
+    }
+
+    return X86_VENDOR_UNKNOWN;
+}
+
 void x86_cpuid_policy_fill_native(struct cpuid_policy *p)
 {
     unsigned int i;

xen/lib/x86/private.h

@@ -23,6 +23,7 @@
 #include <stddef.h>
 
 #include <xen/asm/msr-index.h>
+#include <xen/asm/x86-vendors.h>
 
 #include <xen-tools/libs.h>