[PATCH v3 0/4] RISC-V: hwprobe: Introduce which-cpus

[PATCH v3 0/4] RISC-V: hwprobe: Introduce which-cpus

[Andrew Jones]

This series introduces a flag for the hwprobe syscall which effectively
reverses its behavior from getting the values of keys for a set of cpus
to getting the cpus for a set of key-value pairs.

Change since v2[1]:
 - Rebased on v6.7-rc1 to get green on patchwork (dropped a couple
   patches that were merged with [2])
 - Added an r-b from Conor

Changes since v1[3]:
 - Dropped copyrights when splitting hwprobe out of sys_riscv.c [Conor]
 - Improved documentation [Evan]
 - Fixed a bug where the set of cpus could get changed to the set of all
   online cpus [Evan]
 - Added check for empty set of cpus in the vdso function [Evan, drew]
 - Replaced memset with a for-loop in the vdso function because we don't
   have memset there [drew]
 - Added an r-b from Conor

Changes since the RFC[4]:
 - Split hwprobe out of sys_riscv.c into its own file [Palmer]
 - Split the which-cpus functionality out of do_riscv_hwprobe() [Palmer]
 - Rename hwprobe_key_is_map to hwprobe_key_is_bitmask [Evan]
 - Move the homogeneous_cpus logic into the vDSO function [Evan]
 - Rework logic to not need to allocate any memory
 - Honor cpu affinity in the which-cpus selftests utility
 - Picked up some r-b's

[1] https://lore.kernel.org/all/20231020130515.424577-8-ajones@ventanamicro.com/
[2] https://lore.kernel.org/all/20230918131518.56803-8-ajones@ventanamicro.com/
[3] https://lore.kernel.org/all/20231011135610.122850-8-ajones@ventanamicro.com/
[4] https://lore.kernel.org/all/20230921125518.175428-7-ajones@ventanamicro.com/

Andrew Jones (4):
  RISC-V: hwprobe: Clarify cpus size parameter
  RISC-V: Move the hwprobe syscall to its own file
  RISC-V: hwprobe: Introduce which-cpus flag
  RISC-V: selftests: Add which-cpus hwprobe test

 Documentation/arch/riscv/hwprobe.rst          |  28 +-
 arch/riscv/include/asm/hwprobe.h              |  24 ++
 arch/riscv/include/uapi/asm/hwprobe.h         |   3 +
 arch/riscv/kernel/Makefile                    |   1 +
 arch/riscv/kernel/sys_hwprobe.c               | 375 ++++++++++++++++++
 arch/riscv/kernel/sys_riscv.c                 | 285 -------------
 arch/riscv/kernel/vdso/hwprobe.c              |  86 +++-
 .../testing/selftests/riscv/hwprobe/Makefile  |   5 +-
 .../testing/selftests/riscv/hwprobe/hwprobe.c |   2 +-
 .../testing/selftests/riscv/hwprobe/hwprobe.h |   2 +-
 .../selftests/riscv/hwprobe/which-cpus.c      | 154 +++++++
 .../selftests/riscv/vector/vstate_prctl.c     |  10 +-
 12 files changed, 660 insertions(+), 315 deletions(-)
 create mode 100644 arch/riscv/kernel/sys_hwprobe.c
 create mode 100644 tools/testing/selftests/riscv/hwprobe/which-cpus.c

-- 
2.41.0


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[PATCH v3 1/4] RISC-V: hwprobe: Clarify cpus size parameter

[Andrew Jones]

The "count" parameter associated with the 'cpus' parameter of the
hwprobe syscall is the size in bytes of 'cpus'. Naming it 'cpu_count'
may mislead users (it did me) to think it's the number of CPUs that
are or can be represented by 'cpus' instead. This is particularly
easy (IMO) to get wrong since 'cpus' is documented to be defined by
CPU_SET(3) and CPU_SET(3) also documents a CPU_COUNT() (the number
of CPUs in set) macro. CPU_SET(3) refers to the size of cpu sets
with 'setsize'. Adopt 'cpusetsize' for the hwprobe parameter and
specifically state it is in bytes in Documentation/riscv/hwprobe.rst
to clarify.

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 Documentation/arch/riscv/hwprobe.rst              | 15 ++++++++-------
 arch/riscv/kernel/sys_riscv.c                     | 14 +++++++-------
 arch/riscv/kernel/vdso/hwprobe.c                  | 10 +++++-----
 tools/testing/selftests/riscv/hwprobe/hwprobe.c   |  2 +-
 tools/testing/selftests/riscv/hwprobe/hwprobe.h   |  2 +-
 .../testing/selftests/riscv/vector/vstate_prctl.c | 10 +---------
 6 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index 7b2384de471f..132e9acaa8f4 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -12,7 +12,7 @@ is defined in <asm/hwprobe.h>::
     };
 
     long sys_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-                           size_t cpu_count, cpu_set_t *cpus,
+                           size_t cpusetsize, cpu_set_t *cpus,
                            unsigned int flags);
 
 The arguments are split into three groups: an array of key-value pairs, a CPU
@@ -20,12 +20,13 @@ set, and some flags. The key-value pairs are supplied with a count. Userspace
 must prepopulate the key field for each element, and the kernel will fill in the
 value if the key is recognized. If a key is unknown to the kernel, its key field
 will be cleared to -1, and its value set to 0. The CPU set is defined by
-CPU_SET(3). For value-like keys (eg. vendor/arch/impl), the returned value will
-be only be valid if all CPUs in the given set have the same value. Otherwise -1
-will be returned. For boolean-like keys, the value returned will be a logical
-AND of the values for the specified CPUs. Usermode can supply NULL for cpus and
-0 for cpu_count as a shortcut for all online CPUs. There are currently no flags,
-this value must be zero for future compatibility.
+CPU_SET(3) with size ``cpusetsize`` bytes. For value-like keys (eg. vendor,
+arch, impl), the returned value will only be valid if all CPUs in the given set
+have the same value. Otherwise -1 will be returned. For boolean-like keys, the
+value returned will be a logical AND of the values for the specified CPUs.
+Usermode can supply NULL for ``cpus`` and 0 for ``cpusetsize`` as a shortcut for
+all online CPUs. There are currently no flags, this value must be zero for
+future compatibility.
 
 On success 0 is returned, on failure a negative error code is returned.
 
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index c712037dbe10..5e4deb1308b8 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -246,7 +246,7 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 }
 
 static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
-			    size_t pair_count, size_t cpu_count,
+			    size_t pair_count, size_t cpusetsize,
 			    unsigned long __user *cpus_user,
 			    unsigned int flags)
 {
@@ -264,13 +264,13 @@ static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
 	 * 0 as a shortcut to all online CPUs.
 	 */
 	cpumask_clear(&cpus);
-	if (!cpu_count && !cpus_user) {
+	if (!cpusetsize && !cpus_user) {
 		cpumask_copy(&cpus, cpu_online_mask);
 	} else {
-		if (cpu_count > cpumask_size())
-			cpu_count = cpumask_size();
+		if (cpusetsize > cpumask_size())
+			cpusetsize = cpumask_size();
 
-		ret = copy_from_user(&cpus, cpus_user, cpu_count);
+		ret = copy_from_user(&cpus, cpus_user, cpusetsize);
 		if (ret)
 			return -EFAULT;
 
@@ -347,10 +347,10 @@ arch_initcall_sync(init_hwprobe_vdso_data);
 #endif /* CONFIG_MMU */
 
 SYSCALL_DEFINE5(riscv_hwprobe, struct riscv_hwprobe __user *, pairs,
-		size_t, pair_count, size_t, cpu_count, unsigned long __user *,
+		size_t, pair_count, size_t, cpusetsize, unsigned long __user *,
 		cpus, unsigned int, flags)
 {
-	return do_riscv_hwprobe(pairs, pair_count, cpu_count,
+	return do_riscv_hwprobe(pairs, pair_count, cpusetsize,
 				cpus, flags);
 }
 
diff --git a/arch/riscv/kernel/vdso/hwprobe.c b/arch/riscv/kernel/vdso/hwprobe.c
index cadf725ef798..026b7645c5ab 100644
--- a/arch/riscv/kernel/vdso/hwprobe.c
+++ b/arch/riscv/kernel/vdso/hwprobe.c
@@ -8,21 +8,21 @@
 #include <vdso/helpers.h>
 
 extern int riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-			 size_t cpu_count, unsigned long *cpus,
+			 size_t cpusetsize, unsigned long *cpus,
 			 unsigned int flags);
 
 /* Add a prototype to avoid -Wmissing-prototypes warning. */
 int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-			 size_t cpu_count, unsigned long *cpus,
+			 size_t cpusetsize, unsigned long *cpus,
 			 unsigned int flags);
 
 int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-			 size_t cpu_count, unsigned long *cpus,
+			 size_t cpusetsize, unsigned long *cpus,
 			 unsigned int flags)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
 	const struct arch_vdso_data *avd = &vd->arch_data;
-	bool all_cpus = !cpu_count && !cpus;
+	bool all_cpus = !cpusetsize && !cpus;
 	struct riscv_hwprobe *p = pairs;
 	struct riscv_hwprobe *end = pairs + pair_count;
 
@@ -33,7 +33,7 @@ int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
 	 * masks.
 	 */
 	if ((flags != 0) || (!all_cpus && !avd->homogeneous_cpus))
-		return riscv_hwprobe(pairs, pair_count, cpu_count, cpus, flags);
+		return riscv_hwprobe(pairs, pair_count, cpusetsize, cpus, flags);
 
 	/* This is something we can handle, fill out the pairs. */
 	while (p < end) {
diff --git a/tools/testing/selftests/riscv/hwprobe/hwprobe.c b/tools/testing/selftests/riscv/hwprobe/hwprobe.c
index c474891df307..d53e0889b59e 100644
--- a/tools/testing/selftests/riscv/hwprobe/hwprobe.c
+++ b/tools/testing/selftests/riscv/hwprobe/hwprobe.c
@@ -47,7 +47,7 @@ int main(int argc, char **argv)
 	ksft_test_result(out != 0, "Bad CPU set\n");
 
 	out = riscv_hwprobe(pairs, 8, 1, 0, 0);
-	ksft_test_result(out != 0, "NULL CPU set with non-zero count\n");
+	ksft_test_result(out != 0, "NULL CPU set with non-zero size\n");
 
 	pairs[0].key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR;
 	out = riscv_hwprobe(pairs, 1, 1, &cpus, 0);
diff --git a/tools/testing/selftests/riscv/hwprobe/hwprobe.h b/tools/testing/selftests/riscv/hwprobe/hwprobe.h
index 721b0ce73a56..e3fccb390c4d 100644
--- a/tools/testing/selftests/riscv/hwprobe/hwprobe.h
+++ b/tools/testing/selftests/riscv/hwprobe/hwprobe.h
@@ -10,6 +10,6 @@
  * contain the call.
  */
 long riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-		   size_t cpu_count, unsigned long *cpus, unsigned int flags);
+		   size_t cpusetsize, unsigned long *cpus, unsigned int flags);
 
 #endif
diff --git a/tools/testing/selftests/riscv/vector/vstate_prctl.c b/tools/testing/selftests/riscv/vector/vstate_prctl.c
index b348b475be57..8dcd399ef7fc 100644
--- a/tools/testing/selftests/riscv/vector/vstate_prctl.c
+++ b/tools/testing/selftests/riscv/vector/vstate_prctl.c
@@ -1,20 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-only
 #include <sys/prctl.h>
 #include <unistd.h>
-#include <asm/hwprobe.h>
 #include <errno.h>
 #include <sys/wait.h>
 
+#include "../hwprobe/hwprobe.h"
 #include "../../kselftest.h"
 
-/*
- * Rather than relying on having a new enough libc to define this, just do it
- * ourselves.  This way we don't need to be coupled to a new-enough libc to
- * contain the call.
- */
-long riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-		   size_t cpu_count, unsigned long *cpus, unsigned int flags);
-
 #define NEXT_PROGRAM "./vstate_exec_nolibc"
 static int launch_test(int test_inherit)
 {
-- 
2.41.0


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[PATCH v3 2/4] RISC-V: Move the hwprobe syscall to its own file

[Andrew Jones]

As Palmer says, hwprobe is "sort of its own thing now, and it's only
going to get bigger..."

Suggested-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/kernel/Makefile      |   1 +
 arch/riscv/kernel/sys_hwprobe.c | 289 ++++++++++++++++++++++++++++++++
 arch/riscv/kernel/sys_riscv.c   | 285 -------------------------------
 3 files changed, 290 insertions(+), 285 deletions(-)
 create mode 100644 arch/riscv/kernel/sys_hwprobe.c

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index fee22a3d1b53..a1f5dc145574 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -50,6 +50,7 @@ obj-y	+= setup.o
 obj-y	+= signal.o
 obj-y	+= syscall_table.o
 obj-y	+= sys_riscv.o
+obj-y	+= sys_hwprobe.o
 obj-y	+= time.o
 obj-y	+= traps.o
 obj-y	+= riscv_ksyms.o
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
new file mode 100644
index 000000000000..c0ccf1f45aaa
--- /dev/null
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -0,0 +1,289 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The hwprobe interface, for allowing userspace to probe to see which features
+ * are supported by the hardware.  See Documentation/arch/riscv/hwprobe.rst for
+ * more details.
+ */
+#include <linux/syscalls.h>
+#include <asm/cacheflush.h>
+#include <asm/cpufeature.h>
+#include <asm/hwprobe.h>
+#include <asm/sbi.h>
+#include <asm/switch_to.h>
+#include <asm/uaccess.h>
+#include <asm/unistd.h>
+#include <asm/vector.h>
+#include <vdso/vsyscall.h>
+
+
+static void hwprobe_arch_id(struct riscv_hwprobe *pair,
+			    const struct cpumask *cpus)
+{
+	u64 id = -1ULL;
+	bool first = true;
+	int cpu;
+
+	for_each_cpu(cpu, cpus) {
+		u64 cpu_id;
+
+		switch (pair->key) {
+		case RISCV_HWPROBE_KEY_MVENDORID:
+			cpu_id = riscv_cached_mvendorid(cpu);
+			break;
+		case RISCV_HWPROBE_KEY_MIMPID:
+			cpu_id = riscv_cached_mimpid(cpu);
+			break;
+		case RISCV_HWPROBE_KEY_MARCHID:
+			cpu_id = riscv_cached_marchid(cpu);
+			break;
+		}
+
+		if (first) {
+			id = cpu_id;
+			first = false;
+		}
+
+		/*
+		 * If there's a mismatch for the given set, return -1 in the
+		 * value.
+		 */
+		if (id != cpu_id) {
+			id = -1ULL;
+			break;
+		}
+	}
+
+	pair->value = id;
+}
+
+static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
+			     const struct cpumask *cpus)
+{
+	int cpu;
+	u64 missing = 0;
+
+	pair->value = 0;
+	if (has_fpu())
+		pair->value |= RISCV_HWPROBE_IMA_FD;
+
+	if (riscv_isa_extension_available(NULL, c))
+		pair->value |= RISCV_HWPROBE_IMA_C;
+
+	if (has_vector())
+		pair->value |= RISCV_HWPROBE_IMA_V;
+
+	/*
+	 * Loop through and record extensions that 1) anyone has, and 2) anyone
+	 * doesn't have.
+	 */
+	for_each_cpu(cpu, cpus) {
+		struct riscv_isainfo *isainfo = &hart_isa[cpu];
+
+#define EXT_KEY(ext)									\
+	do {										\
+		if (__riscv_isa_extension_available(isainfo->isa, RISCV_ISA_EXT_##ext))	\
+			pair->value |= RISCV_HWPROBE_EXT_##ext;				\
+		else									\
+			missing |= RISCV_HWPROBE_EXT_##ext;				\
+	} while (false)
+
+		/*
+		 * Only use 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_isa bitmap, are made.
+		 */
+		EXT_KEY(ZBA);
+		EXT_KEY(ZBB);
+		EXT_KEY(ZBS);
+		EXT_KEY(ZICBOZ);
+#undef 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;
+
+	hwprobe_isa_ext0(&pair, cpus);
+	return (pair.value & ext);
+}
+
+static u64 hwprobe_misaligned(const struct cpumask *cpus)
+{
+	int cpu;
+	u64 perf = -1ULL;
+
+	for_each_cpu(cpu, cpus) {
+		int this_perf = per_cpu(misaligned_access_speed, cpu);
+
+		if (perf == -1ULL)
+			perf = this_perf;
+
+		if (perf != this_perf) {
+			perf = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
+			break;
+		}
+	}
+
+	if (perf == -1ULL)
+		return RISCV_HWPROBE_MISALIGNED_UNKNOWN;
+
+	return perf;
+}
+
+static void hwprobe_one_pair(struct riscv_hwprobe *pair,
+			     const struct cpumask *cpus)
+{
+	switch (pair->key) {
+	case RISCV_HWPROBE_KEY_MVENDORID:
+	case RISCV_HWPROBE_KEY_MARCHID:
+	case RISCV_HWPROBE_KEY_MIMPID:
+		hwprobe_arch_id(pair, cpus);
+		break;
+	/*
+	 * The kernel already assumes that the base single-letter ISA
+	 * extensions are supported on all harts, and only supports the
+	 * IMA base, so just cheat a bit here and tell that to
+	 * userspace.
+	 */
+	case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
+		pair->value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA;
+		break;
+
+	case RISCV_HWPROBE_KEY_IMA_EXT_0:
+		hwprobe_isa_ext0(pair, cpus);
+		break;
+
+	case RISCV_HWPROBE_KEY_CPUPERF_0:
+		pair->value = hwprobe_misaligned(cpus);
+		break;
+
+	case RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE:
+		pair->value = 0;
+		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
+			pair->value = riscv_cboz_block_size;
+		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
+	 * indicating they're unrecognized.
+	 */
+	default:
+		pair->key = -1;
+		pair->value = 0;
+		break;
+	}
+}
+
+static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
+			    size_t pair_count, size_t cpusetsize,
+			    unsigned long __user *cpus_user,
+			    unsigned int flags)
+{
+	size_t out;
+	int ret;
+	cpumask_t cpus;
+
+	/* Check the reserved flags. */
+	if (flags != 0)
+		return -EINVAL;
+
+	/*
+	 * The interface supports taking in a CPU mask, and returns values that
+	 * are consistent across that mask. Allow userspace to specify NULL and
+	 * 0 as a shortcut to all online CPUs.
+	 */
+	cpumask_clear(&cpus);
+	if (!cpusetsize && !cpus_user) {
+		cpumask_copy(&cpus, cpu_online_mask);
+	} else {
+		if (cpusetsize > cpumask_size())
+			cpusetsize = cpumask_size();
+
+		ret = copy_from_user(&cpus, cpus_user, cpusetsize);
+		if (ret)
+			return -EFAULT;
+
+		/*
+		 * Userspace must provide at least one online CPU, without that
+		 * there's no way to define what is supported.
+		 */
+		cpumask_and(&cpus, &cpus, cpu_online_mask);
+		if (cpumask_empty(&cpus))
+			return -EINVAL;
+	}
+
+	for (out = 0; out < pair_count; out++, pairs++) {
+		struct riscv_hwprobe pair;
+
+		if (get_user(pair.key, &pairs->key))
+			return -EFAULT;
+
+		pair.value = 0;
+		hwprobe_one_pair(&pair, &cpus);
+		ret = put_user(pair.key, &pairs->key);
+		if (ret == 0)
+			ret = put_user(pair.value, &pairs->value);
+
+		if (ret)
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_MMU
+
+static int __init init_hwprobe_vdso_data(void)
+{
+	struct vdso_data *vd = __arch_get_k_vdso_data();
+	struct arch_vdso_data *avd = &vd->arch_data;
+	u64 id_bitsmash = 0;
+	struct riscv_hwprobe pair;
+	int key;
+
+	/*
+	 * Initialize vDSO data with the answers for the "all CPUs" case, to
+	 * save a syscall in the common case.
+	 */
+	for (key = 0; key <= RISCV_HWPROBE_MAX_KEY; key++) {
+		pair.key = key;
+		hwprobe_one_pair(&pair, cpu_online_mask);
+
+		WARN_ON_ONCE(pair.key < 0);
+
+		avd->all_cpu_hwprobe_values[key] = pair.value;
+		/*
+		 * Smash together the vendor, arch, and impl IDs to see if
+		 * they're all 0 or any negative.
+		 */
+		if (key <= RISCV_HWPROBE_KEY_MIMPID)
+			id_bitsmash |= pair.value;
+	}
+
+	/*
+	 * If the arch, vendor, and implementation ID are all the same across
+	 * all harts, then assume all CPUs are the same, and allow the vDSO to
+	 * answer queries for arbitrary masks. However if all values are 0 (not
+	 * populated) or any value returns -1 (varies across CPUs), then the
+	 * vDSO should defer to the kernel for exotic cpu masks.
+	 */
+	avd->homogeneous_cpus = id_bitsmash != 0 && id_bitsmash != -1;
+	return 0;
+}
+
+arch_initcall_sync(init_hwprobe_vdso_data);
+
+#endif /* CONFIG_MMU */
+
+SYSCALL_DEFINE5(riscv_hwprobe, struct riscv_hwprobe __user *, pairs,
+		size_t, pair_count, size_t, cpusetsize, unsigned long __user *,
+		cpus, unsigned int, flags)
+{
+	return do_riscv_hwprobe(pairs, pair_count, cpusetsize,
+				cpus, flags);
+}
diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c
index 5e4deb1308b8..f1c1416a9f1e 100644
--- a/arch/riscv/kernel/sys_riscv.c
+++ b/arch/riscv/kernel/sys_riscv.c
@@ -7,15 +7,7 @@
 
 #include <linux/syscalls.h>
 #include <asm/cacheflush.h>
-#include <asm/cpufeature.h>
-#include <asm/hwprobe.h>
-#include <asm/sbi.h>
-#include <asm/vector.h>
-#include <asm/switch_to.h>
-#include <asm/uaccess.h>
-#include <asm/unistd.h>
 #include <asm-generic/mman-common.h>
-#include <vdso/vsyscall.h>
 
 static long riscv_sys_mmap(unsigned long addr, unsigned long len,
 			   unsigned long prot, unsigned long flags,
@@ -77,283 +69,6 @@ SYSCALL_DEFINE3(riscv_flush_icache, uintptr_t, start, uintptr_t, end,
 	return 0;
 }
 
-/*
- * The hwprobe interface, for allowing userspace to probe to see which features
- * are supported by the hardware.  See Documentation/arch/riscv/hwprobe.rst for more
- * details.
- */
-static void hwprobe_arch_id(struct riscv_hwprobe *pair,
-			    const struct cpumask *cpus)
-{
-	u64 id = -1ULL;
-	bool first = true;
-	int cpu;
-
-	for_each_cpu(cpu, cpus) {
-		u64 cpu_id;
-
-		switch (pair->key) {
-		case RISCV_HWPROBE_KEY_MVENDORID:
-			cpu_id = riscv_cached_mvendorid(cpu);
-			break;
-		case RISCV_HWPROBE_KEY_MIMPID:
-			cpu_id = riscv_cached_mimpid(cpu);
-			break;
-		case RISCV_HWPROBE_KEY_MARCHID:
-			cpu_id = riscv_cached_marchid(cpu);
-			break;
-		}
-
-		if (first) {
-			id = cpu_id;
-			first = false;
-		}
-
-		/*
-		 * If there's a mismatch for the given set, return -1 in the
-		 * value.
-		 */
-		if (id != cpu_id) {
-			id = -1ULL;
-			break;
-		}
-	}
-
-	pair->value = id;
-}
-
-static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
-			     const struct cpumask *cpus)
-{
-	int cpu;
-	u64 missing = 0;
-
-	pair->value = 0;
-	if (has_fpu())
-		pair->value |= RISCV_HWPROBE_IMA_FD;
-
-	if (riscv_isa_extension_available(NULL, c))
-		pair->value |= RISCV_HWPROBE_IMA_C;
-
-	if (has_vector())
-		pair->value |= RISCV_HWPROBE_IMA_V;
-
-	/*
-	 * Loop through and record extensions that 1) anyone has, and 2) anyone
-	 * doesn't have.
-	 */
-	for_each_cpu(cpu, cpus) {
-		struct riscv_isainfo *isainfo = &hart_isa[cpu];
-
-#define EXT_KEY(ext)									\
-	do {										\
-		if (__riscv_isa_extension_available(isainfo->isa, RISCV_ISA_EXT_##ext))	\
-			pair->value |= RISCV_HWPROBE_EXT_##ext;				\
-		else									\
-			missing |= RISCV_HWPROBE_EXT_##ext;				\
-	} while (false)
-
-		/*
-		 * Only use 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_isa bitmap, are made.
-		 */
-		EXT_KEY(ZBA);
-		EXT_KEY(ZBB);
-		EXT_KEY(ZBS);
-		EXT_KEY(ZICBOZ);
-#undef 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;
-
-	hwprobe_isa_ext0(&pair, cpus);
-	return (pair.value & ext);
-}
-
-static u64 hwprobe_misaligned(const struct cpumask *cpus)
-{
-	int cpu;
-	u64 perf = -1ULL;
-
-	for_each_cpu(cpu, cpus) {
-		int this_perf = per_cpu(misaligned_access_speed, cpu);
-
-		if (perf == -1ULL)
-			perf = this_perf;
-
-		if (perf != this_perf) {
-			perf = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
-			break;
-		}
-	}
-
-	if (perf == -1ULL)
-		return RISCV_HWPROBE_MISALIGNED_UNKNOWN;
-
-	return perf;
-}
-
-static void hwprobe_one_pair(struct riscv_hwprobe *pair,
-			     const struct cpumask *cpus)
-{
-	switch (pair->key) {
-	case RISCV_HWPROBE_KEY_MVENDORID:
-	case RISCV_HWPROBE_KEY_MARCHID:
-	case RISCV_HWPROBE_KEY_MIMPID:
-		hwprobe_arch_id(pair, cpus);
-		break;
-	/*
-	 * The kernel already assumes that the base single-letter ISA
-	 * extensions are supported on all harts, and only supports the
-	 * IMA base, so just cheat a bit here and tell that to
-	 * userspace.
-	 */
-	case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
-		pair->value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA;
-		break;
-
-	case RISCV_HWPROBE_KEY_IMA_EXT_0:
-		hwprobe_isa_ext0(pair, cpus);
-		break;
-
-	case RISCV_HWPROBE_KEY_CPUPERF_0:
-		pair->value = hwprobe_misaligned(cpus);
-		break;
-
-	case RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE:
-		pair->value = 0;
-		if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
-			pair->value = riscv_cboz_block_size;
-		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
-	 * indicating they're unrecognized.
-	 */
-	default:
-		pair->key = -1;
-		pair->value = 0;
-		break;
-	}
-}
-
-static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
-			    size_t pair_count, size_t cpusetsize,
-			    unsigned long __user *cpus_user,
-			    unsigned int flags)
-{
-	size_t out;
-	int ret;
-	cpumask_t cpus;
-
-	/* Check the reserved flags. */
-	if (flags != 0)
-		return -EINVAL;
-
-	/*
-	 * The interface supports taking in a CPU mask, and returns values that
-	 * are consistent across that mask. Allow userspace to specify NULL and
-	 * 0 as a shortcut to all online CPUs.
-	 */
-	cpumask_clear(&cpus);
-	if (!cpusetsize && !cpus_user) {
-		cpumask_copy(&cpus, cpu_online_mask);
-	} else {
-		if (cpusetsize > cpumask_size())
-			cpusetsize = cpumask_size();
-
-		ret = copy_from_user(&cpus, cpus_user, cpusetsize);
-		if (ret)
-			return -EFAULT;
-
-		/*
-		 * Userspace must provide at least one online CPU, without that
-		 * there's no way to define what is supported.
-		 */
-		cpumask_and(&cpus, &cpus, cpu_online_mask);
-		if (cpumask_empty(&cpus))
-			return -EINVAL;
-	}
-
-	for (out = 0; out < pair_count; out++, pairs++) {
-		struct riscv_hwprobe pair;
-
-		if (get_user(pair.key, &pairs->key))
-			return -EFAULT;
-
-		pair.value = 0;
-		hwprobe_one_pair(&pair, &cpus);
-		ret = put_user(pair.key, &pairs->key);
-		if (ret == 0)
-			ret = put_user(pair.value, &pairs->value);
-
-		if (ret)
-			return -EFAULT;
-	}
-
-	return 0;
-}
-
-#ifdef CONFIG_MMU
-
-static int __init init_hwprobe_vdso_data(void)
-{
-	struct vdso_data *vd = __arch_get_k_vdso_data();
-	struct arch_vdso_data *avd = &vd->arch_data;
-	u64 id_bitsmash = 0;
-	struct riscv_hwprobe pair;
-	int key;
-
-	/*
-	 * Initialize vDSO data with the answers for the "all CPUs" case, to
-	 * save a syscall in the common case.
-	 */
-	for (key = 0; key <= RISCV_HWPROBE_MAX_KEY; key++) {
-		pair.key = key;
-		hwprobe_one_pair(&pair, cpu_online_mask);
-
-		WARN_ON_ONCE(pair.key < 0);
-
-		avd->all_cpu_hwprobe_values[key] = pair.value;
-		/*
-		 * Smash together the vendor, arch, and impl IDs to see if
-		 * they're all 0 or any negative.
-		 */
-		if (key <= RISCV_HWPROBE_KEY_MIMPID)
-			id_bitsmash |= pair.value;
-	}
-
-	/*
-	 * If the arch, vendor, and implementation ID are all the same across
-	 * all harts, then assume all CPUs are the same, and allow the vDSO to
-	 * answer queries for arbitrary masks. However if all values are 0 (not
-	 * populated) or any value returns -1 (varies across CPUs), then the
-	 * vDSO should defer to the kernel for exotic cpu masks.
-	 */
-	avd->homogeneous_cpus = id_bitsmash != 0 && id_bitsmash != -1;
-	return 0;
-}
-
-arch_initcall_sync(init_hwprobe_vdso_data);
-
-#endif /* CONFIG_MMU */
-
-SYSCALL_DEFINE5(riscv_hwprobe, struct riscv_hwprobe __user *, pairs,
-		size_t, pair_count, size_t, cpusetsize, unsigned long __user *,
-		cpus, unsigned int, flags)
-{
-	return do_riscv_hwprobe(pairs, pair_count, cpusetsize,
-				cpus, flags);
-}
-
 /* Not defined using SYSCALL_DEFINE0 to avoid error injection */
 asmlinkage long __riscv_sys_ni_syscall(const struct pt_regs *__unused)
 {
-- 
2.41.0


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[PATCH v3 3/4] RISC-V: hwprobe: Introduce which-cpus flag

[Andrew Jones]

Introduce the first flag for the hwprobe syscall. The flag basically
reverses its behavior, i.e. instead of populating the values of keys
for a given set of cpus, the set of cpus after the call is the result
of finding a set which supports the values of the keys. In order to
do this, we implement a pair compare function which takes the type of
value (a single value vs. a bitmask of booleans) into consideration.
We also implement vdso support for the new flag.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 Documentation/arch/riscv/hwprobe.rst  | 17 ++++-
 arch/riscv/include/asm/hwprobe.h      | 24 +++++++
 arch/riscv/include/uapi/asm/hwprobe.h |  3 +
 arch/riscv/kernel/sys_hwprobe.c       | 94 +++++++++++++++++++++++++--
 arch/riscv/kernel/vdso/hwprobe.c      | 80 ++++++++++++++++++++---
 5 files changed, 204 insertions(+), 14 deletions(-)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index 132e9acaa8f4..12f9b0a043ac 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -25,8 +25,21 @@ arch, impl), the returned value will only be valid if all CPUs in the given set
 have the same value. Otherwise -1 will be returned. For boolean-like keys, the
 value returned will be a logical AND of the values for the specified CPUs.
 Usermode can supply NULL for ``cpus`` and 0 for ``cpusetsize`` as a shortcut for
-all online CPUs. There are currently no flags, this value must be zero for
-future compatibility.
+all online CPUs. The currently supported flags are:
+
+* :c:macro:`RISCV_HWPROBE_WHICH_CPUS`: This flag basically reverses the behavior
+  of sys_riscv_hwprobe().  Instead of populating the values of keys for a given
+  set of CPUs, the values of each key are given and the set of CPUs is reduced
+  by sys_riscv_hwprobe() to only those which match each of the key-value pairs.
+  How matching is done depends on the key type.  For value-like keys, matching
+  means to be the exact same as the value.  For boolean-like keys, matching
+  means the result of a logical AND of the pair's value with the CPU's value is
+  exactly the same as the pair's value.  Additionally, when ``cpus`` is an empty
+  set, then it is initialized to all online CPUs which fit within it, i.e. the
+  CPU set returned is the reduction of all the online CPUs which can be
+  represented with a CPU set of size ``cpusetsize``.
+
+All other flags are reserved for future compatibility and must be zero.
 
 On success 0 is returned, on failure a negative error code is returned.
 
diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index 5c48f48e79a6..630507dff5ea 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -15,4 +15,28 @@ static inline bool riscv_hwprobe_key_is_valid(__s64 key)
 	return key >= 0 && key <= RISCV_HWPROBE_MAX_KEY;
 }
 
+static inline bool hwprobe_key_is_bitmask(__s64 key)
+{
+	switch (key) {
+	case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
+	case RISCV_HWPROBE_KEY_IMA_EXT_0:
+	case RISCV_HWPROBE_KEY_CPUPERF_0:
+		return true;
+	}
+
+	return false;
+}
+
+static inline bool riscv_hwprobe_pair_cmp(struct riscv_hwprobe *pair,
+					  struct riscv_hwprobe *other_pair)
+{
+	if (pair->key != other_pair->key)
+		return false;
+
+	if (hwprobe_key_is_bitmask(pair->key))
+		return (pair->value & other_pair->value) == other_pair->value;
+
+	return pair->value == other_pair->value;
+}
+
 #endif
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index b659ffcfcdb4..7aa7d5c71e79 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -40,4 +40,7 @@ struct riscv_hwprobe {
 #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE	6
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
+/* Flags */
+#define RISCV_HWPROBE_WHICH_CPUS	(1 << 0)
+
 #endif
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index c0ccf1f45aaa..b7cfb26ce31c 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -179,10 +179,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 	}
 }
 
-static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
-			    size_t pair_count, size_t cpusetsize,
-			    unsigned long __user *cpus_user,
-			    unsigned int flags)
+static int hwprobe_get_values(struct riscv_hwprobe __user *pairs,
+			      size_t pair_count, size_t cpusetsize,
+			      unsigned long __user *cpus_user,
+			      unsigned int flags)
 {
 	size_t out;
 	int ret;
@@ -236,6 +236,92 @@ static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
 	return 0;
 }
 
+static int hwprobe_get_cpus(struct riscv_hwprobe __user *pairs,
+			    size_t pair_count, size_t cpusetsize,
+			    unsigned long __user *cpus_user,
+			    unsigned int flags)
+{
+	cpumask_t cpus, one_cpu;
+	bool clear_all = false;
+	size_t i;
+	int ret;
+
+	if (flags != RISCV_HWPROBE_WHICH_CPUS)
+		return -EINVAL;
+
+	if (!cpusetsize || !cpus_user)
+		return -EINVAL;
+
+	if (cpusetsize > cpumask_size())
+		cpusetsize = cpumask_size();
+
+	ret = copy_from_user(&cpus, cpus_user, cpusetsize);
+	if (ret)
+		return -EFAULT;
+
+	if (cpumask_empty(&cpus))
+		cpumask_copy(&cpus, cpu_online_mask);
+
+	cpumask_and(&cpus, &cpus, cpu_online_mask);
+
+	cpumask_clear(&one_cpu);
+
+	for (i = 0; i < pair_count; i++) {
+		struct riscv_hwprobe pair, tmp;
+		int cpu;
+
+		ret = copy_from_user(&pair, &pairs[i], sizeof(pair));
+		if (ret)
+			return -EFAULT;
+
+		if (!riscv_hwprobe_key_is_valid(pair.key)) {
+			clear_all = true;
+			pair = (struct riscv_hwprobe){ .key = -1, };
+			ret = copy_to_user(&pairs[i], &pair, sizeof(pair));
+			if (ret)
+				return -EFAULT;
+		}
+
+		if (clear_all)
+			continue;
+
+		tmp = (struct riscv_hwprobe){ .key = pair.key, };
+
+		for_each_cpu(cpu, &cpus) {
+			cpumask_set_cpu(cpu, &one_cpu);
+
+			hwprobe_one_pair(&tmp, &one_cpu);
+
+			if (!riscv_hwprobe_pair_cmp(&tmp, &pair))
+				cpumask_clear_cpu(cpu, &cpus);
+
+			cpumask_clear_cpu(cpu, &one_cpu);
+		}
+	}
+
+	if (clear_all)
+		cpumask_clear(&cpus);
+
+	ret = copy_to_user(cpus_user, &cpus, cpusetsize);
+	if (ret)
+		return -EFAULT;
+
+	return 0;
+}
+
+static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
+			    size_t pair_count, size_t cpusetsize,
+			    unsigned long __user *cpus_user,
+			    unsigned int flags)
+{
+	if (flags & RISCV_HWPROBE_WHICH_CPUS)
+		return hwprobe_get_cpus(pairs, pair_count, cpusetsize,
+					cpus_user, flags);
+
+	return hwprobe_get_values(pairs, pair_count, cpusetsize,
+				  cpus_user, flags);
+}
+
 #ifdef CONFIG_MMU
 
 static int __init init_hwprobe_vdso_data(void)
diff --git a/arch/riscv/kernel/vdso/hwprobe.c b/arch/riscv/kernel/vdso/hwprobe.c
index 026b7645c5ab..1e926e4b5881 100644
--- a/arch/riscv/kernel/vdso/hwprobe.c
+++ b/arch/riscv/kernel/vdso/hwprobe.c
@@ -3,6 +3,7 @@
  * Copyright 2023 Rivos, Inc
  */
 
+#include <linux/string.h>
 #include <linux/types.h>
 #include <vdso/datapage.h>
 #include <vdso/helpers.h>
@@ -11,14 +12,9 @@ extern int riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
 			 size_t cpusetsize, unsigned long *cpus,
 			 unsigned int flags);
 
-/* Add a prototype to avoid -Wmissing-prototypes warning. */
-int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-			 size_t cpusetsize, unsigned long *cpus,
-			 unsigned int flags);
-
-int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
-			 size_t cpusetsize, unsigned long *cpus,
-			 unsigned int flags)
+static int riscv_vdso_get_values(struct riscv_hwprobe *pairs, size_t pair_count,
+				 size_t cpusetsize, unsigned long *cpus,
+				 unsigned int flags)
 {
 	const struct vdso_data *vd = __arch_get_vdso_data();
 	const struct arch_vdso_data *avd = &vd->arch_data;
@@ -50,3 +46,71 @@ int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
 
 	return 0;
 }
+
+static int riscv_vdso_get_cpus(struct riscv_hwprobe *pairs, size_t pair_count,
+			       size_t cpusetsize, unsigned long *cpus,
+			       unsigned int flags)
+{
+	const struct vdso_data *vd = __arch_get_vdso_data();
+	const struct arch_vdso_data *avd = &vd->arch_data;
+	struct riscv_hwprobe *p = pairs;
+	struct riscv_hwprobe *end = pairs + pair_count;
+	unsigned char *c = (unsigned char *)cpus;
+	bool empty_cpus = true;
+	bool clear_all = false;
+	int i;
+
+	if (!cpusetsize || !cpus)
+		return -EINVAL;
+
+	for (i = 0; i < cpusetsize; i++) {
+		if (c[i]) {
+			empty_cpus = false;
+			break;
+		}
+	}
+
+	if (empty_cpus || flags != RISCV_HWPROBE_WHICH_CPUS || !avd->homogeneous_cpus)
+		return riscv_hwprobe(pairs, pair_count, cpusetsize, cpus, flags);
+
+	while (p < end) {
+		if (riscv_hwprobe_key_is_valid(p->key)) {
+			struct riscv_hwprobe t = {
+				.key = p->key,
+				.value = avd->all_cpu_hwprobe_values[p->key],
+			};
+
+			if (!riscv_hwprobe_pair_cmp(&t, p))
+				clear_all = true;
+		} else {
+			clear_all = true;
+			p->key = -1;
+			p->value = 0;
+		}
+		p++;
+	}
+
+	if (clear_all) {
+		for (i = 0; i < cpusetsize; i++)
+			c[i] = 0;
+	}
+
+	return 0;
+}
+
+/* Add a prototype to avoid -Wmissing-prototypes warning. */
+int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
+			 size_t cpusetsize, unsigned long *cpus,
+			 unsigned int flags);
+
+int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
+			 size_t cpusetsize, unsigned long *cpus,
+			 unsigned int flags)
+{
+	if (flags & RISCV_HWPROBE_WHICH_CPUS)
+		return riscv_vdso_get_cpus(pairs, pair_count, cpusetsize,
+					   cpus, flags);
+
+	return riscv_vdso_get_values(pairs, pair_count, cpusetsize,
+				     cpus, flags);
+}
-- 
2.41.0


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Re: [PATCH v3 3/4] RISC-V: hwprobe: Introduce which-cpus flag

[Evan Green]

On Wed, Nov 22, 2023 at 8:47 AM Andrew Jones <ajones@ventanamicro.com> wrote:
>
> Introduce the first flag for the hwprobe syscall. The flag basically
> reverses its behavior, i.e. instead of populating the values of keys
> for a given set of cpus, the set of cpus after the call is the result
> of finding a set which supports the values of the keys. In order to
> do this, we implement a pair compare function which takes the type of
> value (a single value vs. a bitmask of booleans) into consideration.
> We also implement vdso support for the new flag.
>
> Signed-off-by: Andrew Jones <ajones@ventanamicro.com>

I spent a little time pondering whether there was a nicer way of
handling unknown keys (rather than rejecting the whole call), but I
can't think of a way that doesn't cause danger and/or extra work for
the happy path. So this looks good to me!

Reviewed-by: Evan Green <evan@rivosinc.com>

> ---
>  Documentation/arch/riscv/hwprobe.rst  | 17 ++++-
>  arch/riscv/include/asm/hwprobe.h      | 24 +++++++
>  arch/riscv/include/uapi/asm/hwprobe.h |  3 +
>  arch/riscv/kernel/sys_hwprobe.c       | 94 +++++++++++++++++++++++++--
>  arch/riscv/kernel/vdso/hwprobe.c      | 80 ++++++++++++++++++++---
>  5 files changed, 204 insertions(+), 14 deletions(-)
>
> diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> index 132e9acaa8f4..12f9b0a043ac 100644
> --- a/Documentation/arch/riscv/hwprobe.rst
> +++ b/Documentation/arch/riscv/hwprobe.rst
> @@ -25,8 +25,21 @@ arch, impl), the returned value will only be valid if all CPUs in the given set
>  have the same value. Otherwise -1 will be returned. For boolean-like keys, the
>  value returned will be a logical AND of the values for the specified CPUs.
>  Usermode can supply NULL for ``cpus`` and 0 for ``cpusetsize`` as a shortcut for
> -all online CPUs. There are currently no flags, this value must be zero for
> -future compatibility.
> +all online CPUs. The currently supported flags are:
> +
> +* :c:macro:`RISCV_HWPROBE_WHICH_CPUS`: This flag basically reverses the behavior
> +  of sys_riscv_hwprobe().  Instead of populating the values of keys for a given
> +  set of CPUs, the values of each key are given and the set of CPUs is reduced
> +  by sys_riscv_hwprobe() to only those which match each of the key-value pairs.
> +  How matching is done depends on the key type.  For value-like keys, matching
> +  means to be the exact same as the value.  For boolean-like keys, matching
> +  means the result of a logical AND of the pair's value with the CPU's value is
> +  exactly the same as the pair's value.  Additionally, when ``cpus`` is an empty
> +  set, then it is initialized to all online CPUs which fit within it, i.e. the
> +  CPU set returned is the reduction of all the online CPUs which can be
> +  represented with a CPU set of size ``cpusetsize``.
> +
> +All other flags are reserved for future compatibility and must be zero.
>
>  On success 0 is returned, on failure a negative error code is returned.
>
> diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
> index 5c48f48e79a6..630507dff5ea 100644
> --- a/arch/riscv/include/asm/hwprobe.h
> +++ b/arch/riscv/include/asm/hwprobe.h
> @@ -15,4 +15,28 @@ static inline bool riscv_hwprobe_key_is_valid(__s64 key)
>         return key >= 0 && key <= RISCV_HWPROBE_MAX_KEY;
>  }
>
> +static inline bool hwprobe_key_is_bitmask(__s64 key)
> +{
> +       switch (key) {
> +       case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:
> +       case RISCV_HWPROBE_KEY_IMA_EXT_0:
> +       case RISCV_HWPROBE_KEY_CPUPERF_0:
> +               return true;
> +       }
> +
> +       return false;
> +}
> +
> +static inline bool riscv_hwprobe_pair_cmp(struct riscv_hwprobe *pair,
> +                                         struct riscv_hwprobe *other_pair)
> +{
> +       if (pair->key != other_pair->key)
> +               return false;
> +
> +       if (hwprobe_key_is_bitmask(pair->key))
> +               return (pair->value & other_pair->value) == other_pair->value;
> +
> +       return pair->value == other_pair->value;
> +}
> +
>  #endif
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index b659ffcfcdb4..7aa7d5c71e79 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -40,4 +40,7 @@ struct riscv_hwprobe {
>  #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE    6
>  /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
>
> +/* Flags */
> +#define RISCV_HWPROBE_WHICH_CPUS       (1 << 0)
> +
>  #endif
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index c0ccf1f45aaa..b7cfb26ce31c 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -179,10 +179,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
>         }
>  }
>
> -static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
> -                           size_t pair_count, size_t cpusetsize,
> -                           unsigned long __user *cpus_user,
> -                           unsigned int flags)
> +static int hwprobe_get_values(struct riscv_hwprobe __user *pairs,
> +                             size_t pair_count, size_t cpusetsize,
> +                             unsigned long __user *cpus_user,
> +                             unsigned int flags)
>  {
>         size_t out;
>         int ret;
> @@ -236,6 +236,92 @@ static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
>         return 0;
>  }
>
> +static int hwprobe_get_cpus(struct riscv_hwprobe __user *pairs,
> +                           size_t pair_count, size_t cpusetsize,
> +                           unsigned long __user *cpus_user,
> +                           unsigned int flags)
> +{
> +       cpumask_t cpus, one_cpu;
> +       bool clear_all = false;
> +       size_t i;
> +       int ret;
> +
> +       if (flags != RISCV_HWPROBE_WHICH_CPUS)
> +               return -EINVAL;
> +
> +       if (!cpusetsize || !cpus_user)
> +               return -EINVAL;
> +
> +       if (cpusetsize > cpumask_size())
> +               cpusetsize = cpumask_size();
> +
> +       ret = copy_from_user(&cpus, cpus_user, cpusetsize);
> +       if (ret)
> +               return -EFAULT;
> +
> +       if (cpumask_empty(&cpus))
> +               cpumask_copy(&cpus, cpu_online_mask);
> +
> +       cpumask_and(&cpus, &cpus, cpu_online_mask);
> +
> +       cpumask_clear(&one_cpu);
> +
> +       for (i = 0; i < pair_count; i++) {
> +               struct riscv_hwprobe pair, tmp;
> +               int cpu;
> +
> +               ret = copy_from_user(&pair, &pairs[i], sizeof(pair));
> +               if (ret)
> +                       return -EFAULT;
> +
> +               if (!riscv_hwprobe_key_is_valid(pair.key)) {
> +                       clear_all = true;
> +                       pair = (struct riscv_hwprobe){ .key = -1, };
> +                       ret = copy_to_user(&pairs[i], &pair, sizeof(pair));
> +                       if (ret)
> +                               return -EFAULT;
> +               }
> +
> +               if (clear_all)
> +                       continue;
> +
> +               tmp = (struct riscv_hwprobe){ .key = pair.key, };
> +
> +               for_each_cpu(cpu, &cpus) {
> +                       cpumask_set_cpu(cpu, &one_cpu);
> +
> +                       hwprobe_one_pair(&tmp, &one_cpu);
> +
> +                       if (!riscv_hwprobe_pair_cmp(&tmp, &pair))
> +                               cpumask_clear_cpu(cpu, &cpus);
> +
> +                       cpumask_clear_cpu(cpu, &one_cpu);
> +               }
> +       }
> +
> +       if (clear_all)
> +               cpumask_clear(&cpus);
> +
> +       ret = copy_to_user(cpus_user, &cpus, cpusetsize);
> +       if (ret)
> +               return -EFAULT;
> +
> +       return 0;
> +}
> +
> +static int do_riscv_hwprobe(struct riscv_hwprobe __user *pairs,
> +                           size_t pair_count, size_t cpusetsize,
> +                           unsigned long __user *cpus_user,
> +                           unsigned int flags)
> +{
> +       if (flags & RISCV_HWPROBE_WHICH_CPUS)
> +               return hwprobe_get_cpus(pairs, pair_count, cpusetsize,
> +                                       cpus_user, flags);
> +
> +       return hwprobe_get_values(pairs, pair_count, cpusetsize,
> +                                 cpus_user, flags);
> +}
> +
>  #ifdef CONFIG_MMU
>
>  static int __init init_hwprobe_vdso_data(void)
> diff --git a/arch/riscv/kernel/vdso/hwprobe.c b/arch/riscv/kernel/vdso/hwprobe.c
> index 026b7645c5ab..1e926e4b5881 100644
> --- a/arch/riscv/kernel/vdso/hwprobe.c
> +++ b/arch/riscv/kernel/vdso/hwprobe.c
> @@ -3,6 +3,7 @@
>   * Copyright 2023 Rivos, Inc
>   */
>
> +#include <linux/string.h>
>  #include <linux/types.h>
>  #include <vdso/datapage.h>
>  #include <vdso/helpers.h>
> @@ -11,14 +12,9 @@ extern int riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
>                          size_t cpusetsize, unsigned long *cpus,
>                          unsigned int flags);
>
> -/* Add a prototype to avoid -Wmissing-prototypes warning. */
> -int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
> -                        size_t cpusetsize, unsigned long *cpus,
> -                        unsigned int flags);
> -
> -int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
> -                        size_t cpusetsize, unsigned long *cpus,
> -                        unsigned int flags)
> +static int riscv_vdso_get_values(struct riscv_hwprobe *pairs, size_t pair_count,
> +                                size_t cpusetsize, unsigned long *cpus,
> +                                unsigned int flags)
>  {
>         const struct vdso_data *vd = __arch_get_vdso_data();
>         const struct arch_vdso_data *avd = &vd->arch_data;
> @@ -50,3 +46,71 @@ int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
>
>         return 0;
>  }
> +
> +static int riscv_vdso_get_cpus(struct riscv_hwprobe *pairs, size_t pair_count,
> +                              size_t cpusetsize, unsigned long *cpus,
> +                              unsigned int flags)
> +{
> +       const struct vdso_data *vd = __arch_get_vdso_data();
> +       const struct arch_vdso_data *avd = &vd->arch_data;
> +       struct riscv_hwprobe *p = pairs;
> +       struct riscv_hwprobe *end = pairs + pair_count;
> +       unsigned char *c = (unsigned char *)cpus;
> +       bool empty_cpus = true;
> +       bool clear_all = false;
> +       int i;
> +
> +       if (!cpusetsize || !cpus)
> +               return -EINVAL;
> +
> +       for (i = 0; i < cpusetsize; i++) {
> +               if (c[i]) {
> +                       empty_cpus = false;
> +                       break;
> +               }
> +       }
> +
> +       if (empty_cpus || flags != RISCV_HWPROBE_WHICH_CPUS || !avd->homogeneous_cpus)
> +               return riscv_hwprobe(pairs, pair_count, cpusetsize, cpus, flags);
> +
> +       while (p < end) {
> +               if (riscv_hwprobe_key_is_valid(p->key)) {
> +                       struct riscv_hwprobe t = {
> +                               .key = p->key,
> +                               .value = avd->all_cpu_hwprobe_values[p->key],
> +                       };
> +
> +                       if (!riscv_hwprobe_pair_cmp(&t, p))
> +                               clear_all = true;
> +               } else {
> +                       clear_all = true;
> +                       p->key = -1;
> +                       p->value = 0;
> +               }
> +               p++;
> +       }
> +
> +       if (clear_all) {
> +               for (i = 0; i < cpusetsize; i++)
> +                       c[i] = 0;
> +       }
> +
> +       return 0;
> +}
> +
> +/* Add a prototype to avoid -Wmissing-prototypes warning. */
> +int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
> +                        size_t cpusetsize, unsigned long *cpus,
> +                        unsigned int flags);
> +
> +int __vdso_riscv_hwprobe(struct riscv_hwprobe *pairs, size_t pair_count,
> +                        size_t cpusetsize, unsigned long *cpus,
> +                        unsigned int flags)
> +{
> +       if (flags & RISCV_HWPROBE_WHICH_CPUS)
> +               return riscv_vdso_get_cpus(pairs, pair_count, cpusetsize,
> +                                          cpus, flags);
> +
> +       return riscv_vdso_get_values(pairs, pair_count, cpusetsize,
> +                                    cpus, flags);
> +}
> --
> 2.41.0
>

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[PATCH v3 4/4] RISC-V: selftests: Add which-cpus hwprobe test

[Andrew Jones]

Test the RISCV_HWPROBE_WHICH_CPUS flag of hwprobe. The test also
has a command line interface in order to get the cpu list for
arbitrary hwprobe pairs.

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 .../testing/selftests/riscv/hwprobe/Makefile  |   5 +-
 .../selftests/riscv/hwprobe/which-cpus.c      | 154 ++++++++++++++++++
 2 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/riscv/hwprobe/which-cpus.c

diff --git a/tools/testing/selftests/riscv/hwprobe/Makefile b/tools/testing/selftests/riscv/hwprobe/Makefile
index f224b84591fb..cec81610a5f2 100644
--- a/tools/testing/selftests/riscv/hwprobe/Makefile
+++ b/tools/testing/selftests/riscv/hwprobe/Makefile
@@ -4,7 +4,7 @@
 
 CFLAGS += -I$(top_srcdir)/tools/include
 
-TEST_GEN_PROGS := hwprobe cbo
+TEST_GEN_PROGS := hwprobe cbo which-cpus
 
 include ../../lib.mk
 
@@ -13,3 +13,6 @@ $(OUTPUT)/hwprobe: hwprobe.c sys_hwprobe.S
 
 $(OUTPUT)/cbo: cbo.c sys_hwprobe.S
 	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
+
+$(OUTPUT)/which-cpus: which-cpus.c sys_hwprobe.S
+	$(CC) -static -o$@ $(CFLAGS) $(LDFLAGS) $^
diff --git a/tools/testing/selftests/riscv/hwprobe/which-cpus.c b/tools/testing/selftests/riscv/hwprobe/which-cpus.c
new file mode 100644
index 000000000000..82c121412dfc
--- /dev/null
+++ b/tools/testing/selftests/riscv/hwprobe/which-cpus.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023 Ventana Micro Systems Inc.
+ *
+ * Test the RISCV_HWPROBE_WHICH_CPUS flag of hwprobe. Also provides a command
+ * line interface to get the cpu list for arbitrary hwprobe pairs.
+ */
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sched.h>
+#include <unistd.h>
+#include <assert.h>
+
+#include "hwprobe.h"
+#include "../../kselftest.h"
+
+static void help(void)
+{
+	printf("\n"
+	       "which-cpus: [-h] [<key=value> [<key=value> ...]]\n\n"
+	       "   Without parameters, tests the RISCV_HWPROBE_WHICH_CPUS flag of hwprobe.\n"
+	       "   With parameters, where each parameter is a hwprobe pair written as\n"
+	       "   <key=value>, outputs the cpulist for cpus which all match the given set\n"
+	       "   of pairs.  'key' and 'value' should be in numeric form, e.g. 4=0x3b\n");
+}
+
+static void print_cpulist(cpu_set_t *cpus)
+{
+	int start = 0, end = 0;
+
+	if (!CPU_COUNT(cpus)) {
+		printf("cpus: None\n");
+		return;
+	}
+
+	printf("cpus:");
+	for (int i = 0, c = 0; i < CPU_COUNT(cpus); i++, c++) {
+		if (start != end && !CPU_ISSET(c, cpus))
+			printf("-%d", end);
+
+		while (!CPU_ISSET(c, cpus))
+			++c;
+
+		if (i != 0 && c == end + 1) {
+			end = c;
+			continue;
+		}
+
+		printf("%c%d", i == 0 ? ' ' : ',', c);
+		start = end = c;
+	}
+	if (start != end)
+		printf("-%d", end);
+	printf("\n");
+}
+
+static void do_which_cpus(int argc, char **argv, cpu_set_t *cpus)
+{
+	struct riscv_hwprobe *pairs;
+	int nr_pairs = argc - 1;
+	char *start, *end;
+	int rc;
+
+	pairs = malloc(nr_pairs * sizeof(struct riscv_hwprobe));
+	assert(pairs);
+
+	for (int i = 0; i < nr_pairs; i++) {
+		start = argv[i + 1];
+		pairs[i].key = strtol(start, &end, 0);
+		assert(end != start && *end == '=');
+		start = end + 1;
+		pairs[i].value = strtoul(start, &end, 0);
+		assert(end != start && *end == '\0');
+	}
+
+	rc = riscv_hwprobe(pairs, nr_pairs, sizeof(cpu_set_t), (unsigned long *)cpus, RISCV_HWPROBE_WHICH_CPUS);
+	assert(rc == 0);
+	print_cpulist(cpus);
+	free(pairs);
+}
+
+int main(int argc, char **argv)
+{
+	struct riscv_hwprobe pairs[2];
+	cpu_set_t cpus_aff, cpus;
+	__u64 ext0_all;
+	long rc;
+
+	rc = sched_getaffinity(0, sizeof(cpu_set_t), &cpus_aff);
+	assert(rc == 0);
+
+	if (argc > 1) {
+		if (!strcmp(argv[1], "-h"))
+			help();
+		else
+			do_which_cpus(argc, argv, &cpus_aff);
+		return 0;
+	}
+
+	ksft_print_header();
+	ksft_set_plan(7);
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, };
+	rc = riscv_hwprobe(pairs, 1, 0, NULL, 0);
+	assert(rc == 0 && pairs[0].key == RISCV_HWPROBE_KEY_BASE_BEHAVIOR &&
+	       pairs[0].value == RISCV_HWPROBE_BASE_BEHAVIOR_IMA);
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_IMA_EXT_0, };
+	rc = riscv_hwprobe(pairs, 1, 0, NULL, 0);
+	assert(rc == 0 && pairs[0].key == RISCV_HWPROBE_KEY_IMA_EXT_0);
+	ext0_all = pairs[0].value;
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	CPU_ZERO(&cpus);
+	rc = riscv_hwprobe(pairs, 1, 0, (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == -EINVAL, "no cpusetsize\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	rc = riscv_hwprobe(pairs, 1, sizeof(cpu_set_t), NULL, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == -EINVAL, "NULL cpus\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = 0xbadc0de, };
+	CPU_ZERO(&cpus);
+	rc = riscv_hwprobe(pairs, 1, sizeof(cpu_set_t), (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == 0 && CPU_COUNT(&cpus) == 0, "unknown key\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	pairs[1] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	CPU_ZERO(&cpus);
+	rc = riscv_hwprobe(pairs, 2, sizeof(cpu_set_t), (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == 0, "duplicate keys\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	pairs[1] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_IMA_EXT_0, .value = ext0_all, };
+	CPU_ZERO(&cpus);
+	rc = riscv_hwprobe(pairs, 2, sizeof(cpu_set_t), (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == 0 && CPU_COUNT(&cpus) == sysconf(_SC_NPROCESSORS_ONLN), "set all cpus\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	pairs[1] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_IMA_EXT_0, .value = ext0_all, };
+	memcpy(&cpus, &cpus_aff, sizeof(cpu_set_t));
+	rc = riscv_hwprobe(pairs, 2, sizeof(cpu_set_t), (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == 0 && CPU_EQUAL(&cpus, &cpus_aff), "set all affinity cpus\n");
+
+	pairs[0] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_BASE_BEHAVIOR, .value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA, };
+	pairs[1] = (struct riscv_hwprobe){ .key = RISCV_HWPROBE_KEY_IMA_EXT_0, .value = ~ext0_all, };
+	memcpy(&cpus, &cpus_aff, sizeof(cpu_set_t));
+	rc = riscv_hwprobe(pairs, 2, sizeof(cpu_set_t), (unsigned long *)&cpus, RISCV_HWPROBE_WHICH_CPUS);
+	ksft_test_result(rc == 0 && CPU_COUNT(&cpus) == 0, "clear all cpus\n");
+
+	ksft_finished();
+}
-- 
2.41.0


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Re: [PATCH v3 0/4] RISC-V: hwprobe: Introduce which-cpus

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Wed, 22 Nov 2023 17:47:01 +0100 you wrote:
> This series introduces a flag for the hwprobe syscall which effectively
> reverses its behavior from getting the values of keys for a set of cpus
> to getting the cpus for a set of key-value pairs.
> 
> Change since v2[1]:
>  - Rebased on v6.7-rc1 to get green on patchwork (dropped a couple
>    patches that were merged with [2])
>  - Added an r-b from Conor
> 
> [...]

Here is the summary with links:
  - [v3,1/4] RISC-V: hwprobe: Clarify cpus size parameter
    https://git.kernel.org/riscv/c/36d842d654be
  - [v3,2/4] RISC-V: Move the hwprobe syscall to its own file
    https://git.kernel.org/riscv/c/53b2b22850e1
  - [v3,3/4] RISC-V: hwprobe: Introduce which-cpus flag
    https://git.kernel.org/riscv/c/e178bf146e4b
  - [v3,4/4] RISC-V: selftests: Add which-cpus hwprobe test
    https://git.kernel.org/riscv/c/ef7d6abb2cf5

You are awesome, thank you!
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