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

Charlie Jenkins
2024-04-12T04:15:59Z

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@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