util/cpuinfo-riscv: Detect Zbs

Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250102181601.1421059-2-richard.henderson@linaro.org>

host/include/riscv/host/cpuinfo.h

@@ -9,8 +9,9 @@
 #define CPUINFO_ALWAYS          (1u << 0)  /* so cpuinfo is nonzero */
 #define CPUINFO_ZBA             (1u << 1)
 #define CPUINFO_ZBB             (1u << 2)
-#define CPUINFO_ZICOND          (1u << 3)
-#define CPUINFO_ZVE64X          (1u << 4)
+#define CPUINFO_ZBS             (1u << 3)
+#define CPUINFO_ZICOND          (1u << 4)
+#define CPUINFO_ZVE64X          (1u << 5)
 
 /* Initialized with a constructor. */
 extern unsigned cpuinfo;

util/cpuinfo-riscv.c

@@ -36,7 +36,8 @@ static void sigill_handler(int signo, siginfo_t *si, void *data)
 /* Called both as constructor and (possibly) via other constructors. */
 unsigned __attribute__((constructor)) cpuinfo_init(void)
 {
-    unsigned left = CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZICOND | CPUINFO_ZVE64X;
+    unsigned left = CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZBS
+                  | CPUINFO_ZICOND | CPUINFO_ZVE64X;
     unsigned info = cpuinfo;
 
     if (info) {
@@ -50,6 +51,9 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
 #if defined(__riscv_arch_test) && defined(__riscv_zbb)
     info |= CPUINFO_ZBB;
 #endif
+#if defined(__riscv_arch_test) && defined(__riscv_zbs)
+    info |= CPUINFO_ZBS;
+#endif
 #if defined(__riscv_arch_test) && defined(__riscv_zicond)
     info |= CPUINFO_ZICOND;
 #endif
@@ -71,7 +75,8 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
             && pair.key >= 0) {
             info |= pair.value & RISCV_HWPROBE_EXT_ZBA ? CPUINFO_ZBA : 0;
             info |= pair.value & RISCV_HWPROBE_EXT_ZBB ? CPUINFO_ZBB : 0;
-            left &= ~(CPUINFO_ZBA | CPUINFO_ZBB);
+            info |= pair.value & RISCV_HWPROBE_EXT_ZBS ? CPUINFO_ZBS : 0;
+            left &= ~(CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZBS);
 #ifdef RISCV_HWPROBE_EXT_ZICOND
             info |= pair.value & RISCV_HWPROBE_EXT_ZICOND ? CPUINFO_ZICOND : 0;
             left &= ~CPUINFO_ZICOND;
@@ -117,6 +122,15 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
             left &= ~CPUINFO_ZBB;
         }
 
+        if (left & CPUINFO_ZBS) {
+            /* Probe for Zbs: bext zero,zero,zero. */
+            got_sigill = 0;
+            asm volatile(".insn r 0x33, 5, 0x24, zero, zero, zero"
+                         : : : "memory");
+            info |= got_sigill ? 0 : CPUINFO_ZBS;
+            left &= ~CPUINFO_ZBS;
+        }
+
         if (left & CPUINFO_ZICOND) {
             /* Probe for Zicond: czero.eqz zero,zero,zero. */
             got_sigill = 0;