From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- drivers/of/cpu.c | 210 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 210 insertions(+) create mode 100644 drivers/of/cpu.c (limited to 'drivers/of/cpu.c') diff --git a/drivers/of/cpu.c b/drivers/of/cpu.c new file mode 100644 index 000000000..bd0e918d6 --- /dev/null +++ b/drivers/of/cpu.c @@ -0,0 +1,210 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include + +/** + * of_get_cpu_hwid - Get the hardware ID from a CPU device node + * + * @cpun: CPU number(logical index) for which device node is required + * @thread: The local thread number to get the hardware ID for. + * + * Return: The hardware ID for the CPU node or ~0ULL if not found. + */ +u64 of_get_cpu_hwid(struct device_node *cpun, unsigned int thread) +{ + const __be32 *cell; + int ac, len; + + ac = of_n_addr_cells(cpun); + cell = of_get_property(cpun, "reg", &len); + if (!cell || !ac || ((sizeof(*cell) * ac * (thread + 1)) > len)) + return ~0ULL; + + cell += ac * thread; + return of_read_number(cell, ac); +} + +/* + * arch_match_cpu_phys_id - Match the given logical CPU and physical id + * + * @cpu: logical cpu index of a core/thread + * @phys_id: physical identifier of a core/thread + * + * CPU logical to physical index mapping is architecture specific. + * However this __weak function provides a default match of physical + * id to logical cpu index. phys_id provided here is usually values read + * from the device tree which must match the hardware internal registers. + * + * Returns true if the physical identifier and the logical cpu index + * correspond to the same core/thread, false otherwise. + */ +bool __weak arch_match_cpu_phys_id(int cpu, u64 phys_id) +{ + return (u32)phys_id == cpu; +} + +/* + * Checks if the given "prop_name" property holds the physical id of the + * core/thread corresponding to the logical cpu 'cpu'. If 'thread' is not + * NULL, local thread number within the core is returned in it. + */ +static bool __of_find_n_match_cpu_property(struct device_node *cpun, + const char *prop_name, int cpu, unsigned int *thread) +{ + const __be32 *cell; + int ac, prop_len, tid; + u64 hwid; + + ac = of_n_addr_cells(cpun); + cell = of_get_property(cpun, prop_name, &prop_len); + if (!cell && !ac && arch_match_cpu_phys_id(cpu, 0)) + return true; + if (!cell || !ac || ac > 2) + return false; + prop_len /= sizeof(*cell) * ac; + for (tid = 0; tid < prop_len; tid++) { + hwid = of_read_number(cell, ac); + if (arch_match_cpu_phys_id(cpu, hwid)) { + if (thread) + *thread = tid; + return true; + } + cell += ac; + } + return false; +} + +/* + * arch_find_n_match_cpu_physical_id - See if the given device node is + * for the cpu corresponding to logical cpu 'cpu'. Return true if so, + * else false. If 'thread' is non-NULL, the local thread number within the + * core is returned in it. + */ +bool __weak arch_find_n_match_cpu_physical_id(struct device_node *cpun, + int cpu, unsigned int *thread) +{ + /* Check for non-standard "ibm,ppc-interrupt-server#s" property + * for thread ids on PowerPC. If it doesn't exist fallback to + * standard "reg" property. + */ + if (IS_ENABLED(CONFIG_PPC) && + __of_find_n_match_cpu_property(cpun, + "ibm,ppc-interrupt-server#s", + cpu, thread)) + return true; + + return __of_find_n_match_cpu_property(cpun, "reg", cpu, thread); +} + +/** + * of_get_cpu_node - Get device node associated with the given logical CPU + * + * @cpu: CPU number(logical index) for which device node is required + * @thread: if not NULL, local thread number within the physical core is + * returned + * + * The main purpose of this function is to retrieve the device node for the + * given logical CPU index. It should be used to initialize the of_node in + * cpu device. Once of_node in cpu device is populated, all the further + * references can use that instead. + * + * CPU logical to physical index mapping is architecture specific and is built + * before booting secondary cores. This function uses arch_match_cpu_phys_id + * which can be overridden by architecture specific implementation. + * + * Return: A node pointer for the logical cpu with refcount incremented, use + * of_node_put() on it when done. Returns NULL if not found. + */ +struct device_node *of_get_cpu_node(int cpu, unsigned int *thread) +{ + struct device_node *cpun; + + for_each_of_cpu_node(cpun) { + if (arch_find_n_match_cpu_physical_id(cpun, cpu, thread)) + return cpun; + } + return NULL; +} +EXPORT_SYMBOL(of_get_cpu_node); + +/** + * of_cpu_device_node_get: Get the CPU device_node for a given logical CPU number + * + * @cpu: The logical CPU number + * + * Return: Pointer to the device_node for CPU with its reference count + * incremented of the given logical CPU number or NULL if the CPU device_node + * is not found. + */ +struct device_node *of_cpu_device_node_get(int cpu) +{ + struct device *cpu_dev; + cpu_dev = get_cpu_device(cpu); + if (!cpu_dev) + return of_get_cpu_node(cpu, NULL); + return of_node_get(cpu_dev->of_node); +} +EXPORT_SYMBOL(of_cpu_device_node_get); + +/** + * of_cpu_node_to_id: Get the logical CPU number for a given device_node + * + * @cpu_node: Pointer to the device_node for CPU. + * + * Return: The logical CPU number of the given CPU device_node or -ENODEV if the + * CPU is not found. + */ +int of_cpu_node_to_id(struct device_node *cpu_node) +{ + int cpu; + bool found = false; + struct device_node *np; + + for_each_possible_cpu(cpu) { + np = of_cpu_device_node_get(cpu); + found = (cpu_node == np); + of_node_put(np); + if (found) + return cpu; + } + + return -ENODEV; +} +EXPORT_SYMBOL(of_cpu_node_to_id); + +/** + * of_get_cpu_state_node - Get CPU's idle state node at the given index + * + * @cpu_node: The device node for the CPU + * @index: The index in the list of the idle states + * + * Two generic methods can be used to describe a CPU's idle states, either via + * a flattened description through the "cpu-idle-states" binding or via the + * hierarchical layout, using the "power-domains" and the "domain-idle-states" + * bindings. This function check for both and returns the idle state node for + * the requested index. + * + * Return: An idle state node if found at @index. The refcount is incremented + * for it, so call of_node_put() on it when done. Returns NULL if not found. + */ +struct device_node *of_get_cpu_state_node(const struct device_node *cpu_node, + int index) +{ + struct of_phandle_args args; + int err; + + err = of_parse_phandle_with_args(cpu_node, "power-domains", + "#power-domain-cells", 0, &args); + if (!err) { + struct device_node *state_node = + of_parse_phandle(args.np, "domain-idle-states", index); + + of_node_put(args.np); + if (state_node) + return state_node; + } + + return of_parse_phandle(cpu_node, "cpu-idle-states", index); +} +EXPORT_SYMBOL(of_get_cpu_state_node); -- cgit v1.3.1