[PATCH 16/19] riscv: hwprobe: Add vendor extension probing

[Charlie Jenkins]

Add a new hwprobe key "RISCV_HWPROBE_KEY_VENDOR_EXT_0" which allows
userspace to probe for the new RISCV_ISA_VENDOR_EXT_XTHEADVECTOR vendor
extension.

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
 arch/riscv/include/asm/hwprobe.h      |  4 +--
 arch/riscv/include/uapi/asm/hwprobe.h | 10 +++++-
 arch/riscv/kernel/sys_hwprobe.c       | 59 +++++++++++++++++++++++++++++++++--
 3 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index 630507dff5ea..e68496b4f8de 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 /*
- * Copyright 2023 Rivos, Inc
+ * Copyright 2023-2024 Rivos, Inc
  */
 
 #ifndef _ASM_HWPROBE_H
@@ -8,7 +8,7 @@
 
 #include <uapi/asm/hwprobe.h>
 
-#define RISCV_HWPROBE_MAX_KEY 6
+#define RISCV_HWPROBE_MAX_KEY 7
 
 static inline bool riscv_hwprobe_key_is_valid(__s64 key)
 {
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 9f2a8e3ff204..6614d3adfc75 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
 /*
- * Copyright 2023 Rivos, Inc
+ * Copyright 2023-2024 Rivos, Inc
  */
 
 #ifndef _UAPI_ASM_HWPROBE_H
@@ -67,6 +67,14 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_MISALIGNED_UNSUPPORTED	(4 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_MASK		(7 << 0)
 #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE	6
+/*
+ * It is not possible for one CPU to have multiple vendor ids, so each vendor
+ * has its own vendor extension "namespace". The keys for each vendor starts
+ * at zero.
+ */
+#define RISCV_HWPROBE_KEY_VENDOR_EXT_0	7
+ /* T-Head */
+#define		RISCV_HWPROBE_VENDOR_EXT_XTHEADVECTOR	(1 << 0)
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
 /* Flags */
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index e0a42c851511..365ce7380443 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -69,7 +69,8 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 	if (riscv_isa_extension_available(NULL, c))
 		pair->value |= RISCV_HWPROBE_IMA_C;
 
-	if (has_vector() && !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR))
+	if (has_vector() &&
+	    !__riscv_isa_vendor_extension_available(NULL, RISCV_ISA_VENDOR_EXT_XTHEADVECTOR))
 		pair->value |= RISCV_HWPROBE_IMA_V;
 
 	/*
@@ -112,7 +113,8 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 		EXT_KEY(ZACAS);
 		EXT_KEY(ZICOND);
 
-		if (has_vector() && !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
+		if (has_vector() &&
+		    !riscv_has_vendor_extension_unlikely(RISCV_ISA_VENDOR_EXT_XTHEADVECTOR)) {
 			EXT_KEY(ZVBB);
 			EXT_KEY(ZVBC);
 			EXT_KEY(ZVKB);
@@ -139,6 +141,55 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 	pair->value &= ~missing;
 }
 
+static void hwprobe_isa_vendor_ext0(struct riscv_hwprobe *pair,
+				    const struct cpumask *cpus)
+{
+	int cpu;
+	u64 missing = 0;
+
+	pair->value = 0;
+
+	struct riscv_hwprobe mvendorid = {
+		.key = RISCV_HWPROBE_KEY_MVENDORID,
+		.value = 0
+	};
+
+	hwprobe_arch_id(&mvendorid, cpus);
+
+	/* Set value to zero if CPUs in the set do not have the same vendor. */
+	if (mvendorid.value == -1ULL)
+		return;
+
+	/*
+	 * Loop through and record vendor extensions that 1) anyone has, and
+	 * 2) anyone doesn't have.
+	 */
+	for_each_cpu(cpu, cpus) {
+		struct riscv_isainfo *isavendorinfo = &hart_isa_vendor[cpu];
+
+#define VENDOR_EXT_KEY(ext)								\
+	do {										\
+		if (__riscv_isa_vendor_extension_available(isavendorinfo->isa,		\
+							 RISCV_ISA_VENDOR_EXT_##ext))	\
+			pair->value |= RISCV_HWPROBE_VENDOR_EXT_##ext;			\
+		else									\
+			missing |= RISCV_HWPROBE_VENDOR_EXT_##ext;			\
+	} while (false)
+
+	/*
+	 * Only use VENDOR_EXT_KEY() for extensions which can be exposed to userspace,
+	 * regardless of the kernel's configuration, as no other checks, besides
+	 * presence in the hart_vendor_isa bitmap, are made.
+	 */
+	VENDOR_EXT_KEY(XTHEADVECTOR);
+
+#undef VENDOR_EXT_KEY
+	}
+
+	/* Now turn off reporting features if any CPU is missing it. */
+	pair->value &= ~missing;
+}
+
 static bool hwprobe_ext0_has(const struct cpumask *cpus, unsigned long ext)
 {
 	struct riscv_hwprobe pair;
@@ -216,6 +267,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 			pair->value = riscv_cboz_block_size;
 		break;
 
+	case RISCV_HWPROBE_KEY_VENDOR_EXT_0:
+		hwprobe_isa_vendor_ext0(pair, cpus);
+		break;
+
 	/*
 	 * For forward compatibility, unknown keys don't fail the whole
 	 * call, but get their element key set to -1 and value set to 0

-- 
2.44.0