RISC-V: hwprobe: Expose Zicbom extension and its block size

Expose Zicbom through hwprobe and also provide a key to extract its
respective block size.

[ alex: Fix merge conflicts and hwprobe numbering ]

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Link: https://lore.kernel.org/r/20250226063206.71216-3-cuiyunhui@bytedance.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>

4 files changed, 16 insertions, 2 deletions

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index 67ef406cdb67..2792f12e90ba 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -260,6 +260,9 @@ The following keys are defined:
        defined in the RISC-V ISA manual starting from commit 4dc23d6229de
        ("Added Chapter title to BF16").
 
+  * :c:macro:`RISCV_HWPROBE_EXT_ZICBOM`: The Zicbom extension is supported, as
+       ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs.
+
 * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: Deprecated.  Returns similar values to
      :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF`, but the key was
      mistakenly classified as a bitmask rather than a value.
@@ -321,3 +324,6 @@ The following keys are defined:
     * :c:macro:`RISCV_HWPROBE_VENDOR_EXT_XTHEADVECTOR`: The xtheadvector vendor
         extension is supported in the T-Head ISA extensions spec starting from
 	commit a18c801634 ("Add T-Head VECTOR vendor extension. ").
+
+* :c:macro:`RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE`: An unsigned int which
+  represents the size of the Zicbom block in bytes.
diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index dd624523981c..1f690fea0e03 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -8,7 +8,7 @@
 
 #include <uapi/asm/hwprobe.h>
 
-#define RISCV_HWPROBE_MAX_KEY 11
+#define RISCV_HWPROBE_MAX_KEY 12
 
 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 08ab52fe8004..056decf65b1b 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -78,6 +78,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_EXT_ZFBFMIN	(1ULL << 52)
 #define		RISCV_HWPROBE_EXT_ZVFBFMIN	(1ULL << 53)
 #define		RISCV_HWPROBE_EXT_ZVFBFWMA	(1ULL << 54)
+#define		RISCV_HWPROBE_EXT_ZICBOM	(1ULL << 55)
 #define RISCV_HWPROBE_KEY_CPUPERF_0	5
 #define		RISCV_HWPROBE_MISALIGNED_UNKNOWN	(0 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_EMULATED	(1 << 0)
@@ -100,6 +101,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_MISALIGNED_VECTOR_FAST		3
 #define		RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED	4
 #define RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0	11
+#define RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE	12
 /* 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 32509111fe0a..cfe6ceaf3069 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -107,6 +107,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 		EXT_KEY(ZCA);
 		EXT_KEY(ZCB);
 		EXT_KEY(ZCMOP);
+		EXT_KEY(ZICBOM);
 		EXT_KEY(ZICBOZ);
 		EXT_KEY(ZICNTR);
 		EXT_KEY(ZICOND);
@@ -166,7 +167,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
 	pair->value &= ~missing;
 }
 
-static bool hwprobe_ext0_has(const struct cpumask *cpus, unsigned long ext)
+static bool hwprobe_ext0_has(const struct cpumask *cpus, u64 ext)
 {
 	struct riscv_hwprobe pair;
 
@@ -284,6 +285,11 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
 			pair->value = riscv_cboz_block_size;
 		break;
+	case RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE:
+		pair->value = 0;
+		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOM))
+			pair->value = riscv_cbom_block_size;
+		break;
 	case RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS:
 		pair->value = user_max_virt_addr();
 		break;