[PATCH v1 3/6] RISC-V: hwprobe: Introduce which-cpus flag

Andrew Jones
2023-10-11T13:56:29Z

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/riscv/hwprobe.rst | 16 ++++-
arch/riscv/include/asm/hwprobe.h | 24 +++++++
arch/riscv/include/uapi/asm/hwprobe.h | 3 +
arch/riscv/kernel/sys_hwprobe.c | 93 +++++++++++++++++++++++++--
arch/riscv/kernel/vdso/hwprobe.c | 68 +++++++++++++++++---
5 files changed, 190 insertions(+), 14 deletions(-)

diff --git a/Documentation/riscv/hwprobe.rst b/Documentation/riscv/hwprobe.rst
index c57437e40ffb..576aa03f56bb 100644
--- a/Documentation/riscv/hwprobe.rst
+++ b/Documentation/riscv/hwprobe.rst
@@ -25,8 +25,20 @@ 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 set of CPUs is initially all unset and the values of each key
+ are given. Upon return, the CPUs which all match each of the given key-value
+ pairs are set in ``cpus``. 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. ``cpus``
+ may also initially have set bits, in which case the bits of any CPUs which do
+ not match the pairs will be cleared, but no other bits will be set.
+
+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 7cad513538d8..a68764149e51 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 006bfb48343d..1d4134befc48 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -38,4 +38,7 @@ struct riscv_hwprobe {
#define RISCV_HWPROBE_MISALIGNED_MASK (7 << 0)
/* 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 69ad5f793374..de294538ca25 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -166,10 +166,10 @@ 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;
@@ -223,6 +223,91 @@ 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;
+
+ cpumask_and(&cpus, &cpus, cpu_online_mask);
+ if (cpumask_empty(&cpus))
+ cpumask_copy(&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..e6c324d64544 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 +46,59 @@ 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;
+ bool clear_all = false;
+
+ if (!cpusetsize || !cpus)
+ return -EINVAL;
+
+ if (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)
+ memset(cpus, 0, cpusetsize);
+
+ 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