sched_ext: Maintain an online cid mask in the scheduler arenagrafted

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 <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 317 insertions, 0 deletions

diff --git a/lib/logic_pio.c b/lib/logic_pio.c
new file mode 100644
index 000000000..e29496a38
--- /dev/null
+++ b/lib/logic_pio.c
@@ -0,0 +1,317 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 HiSilicon Limited, All Rights Reserved.
+ * Author: Gabriele Paoloni <gabriele.paoloni@huawei.com>
+ * Author: Zhichang Yuan <yuanzhichang@hisilicon.com>
+ * Author: John Garry <john.garry@huawei.com>
+ */
+
+#define pr_fmt(fmt)	"LOGIC PIO: " fmt
+
+#include <linux/of.h>
+#include <linux/io.h>
+#include <linux/logic_pio.h>
+#include <linux/mm.h>
+#include <linux/rculist.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+
+/* The unique hardware address list */
+static LIST_HEAD(io_range_list);
+static DEFINE_MUTEX(io_range_mutex);
+
+/**
+ * logic_pio_register_range - register logical PIO range for a host
+ * @new_range: pointer to the IO range to be registered.
+ *
+ * Returns 0 on success, the error code in case of failure.
+ * If the range already exists, -EEXIST will be returned, which should be
+ * considered a success.
+ *
+ * Register a new IO range node in the IO range list.
+ */
+int logic_pio_register_range(struct logic_pio_hwaddr *new_range)
+{
+	struct logic_pio_hwaddr *range;
+	resource_size_t start;
+	resource_size_t end;
+	resource_size_t mmio_end = 0;
+	resource_size_t iio_sz = MMIO_UPPER_LIMIT;
+	int ret = 0;
+
+	if (!new_range || !new_range->fwnode || !new_range->size ||
+	    (new_range->flags == LOGIC_PIO_INDIRECT && !new_range->ops))
+		return -EINVAL;
+
+	start = new_range->hw_start;
+	end = new_range->hw_start + new_range->size;
+
+	mutex_lock(&io_range_mutex);
+	list_for_each_entry(range, &io_range_list, list) {
+		if (range->fwnode == new_range->fwnode) {
+			/* range already there */
+			ret = -EEXIST;
+			goto end_register;
+		}
+		if (range->flags == LOGIC_PIO_CPU_MMIO &&
+		    new_range->flags == LOGIC_PIO_CPU_MMIO) {
+			/* for MMIO ranges we need to check for overlap */
+			if (start >= range->hw_start + range->size ||
+			    end < range->hw_start) {
+				mmio_end = range->io_start + range->size;
+			} else {
+				ret = -EFAULT;
+				goto end_register;
+			}
+		} else if (range->flags == LOGIC_PIO_INDIRECT &&
+			   new_range->flags == LOGIC_PIO_INDIRECT) {
+			iio_sz += range->size;
+		}
+	}
+
+	/* range not registered yet, check for available space */
+	if (new_range->flags == LOGIC_PIO_CPU_MMIO) {
+		if (mmio_end + new_range->size - 1 > MMIO_UPPER_LIMIT) {
+			/* if it's too big check if 64K space can be reserved */
+			if (mmio_end + SZ_64K - 1 > MMIO_UPPER_LIMIT) {
+				ret = -E2BIG;
+				goto end_register;
+			}
+			new_range->size = SZ_64K;
+			pr_warn("Requested IO range too big, new size set to 64K\n");
+		}
+		new_range->io_start = mmio_end;
+	} else if (new_range->flags == LOGIC_PIO_INDIRECT) {
+		if (iio_sz + new_range->size - 1 > IO_SPACE_LIMIT) {
+			ret = -E2BIG;
+			goto end_register;
+		}
+		new_range->io_start = iio_sz;
+	} else {
+		/* invalid flag */
+		ret = -EINVAL;
+		goto end_register;
+	}
+
+	list_add_tail_rcu(&new_range->list, &io_range_list);
+
+end_register:
+	mutex_unlock(&io_range_mutex);
+	return ret;
+}
+
+/**
+ * logic_pio_unregister_range - unregister a logical PIO range for a host
+ * @range: pointer to the IO range which has been already registered.
+ *
+ * Unregister a previously-registered IO range node.
+ */
+void logic_pio_unregister_range(struct logic_pio_hwaddr *range)
+{
+	mutex_lock(&io_range_mutex);
+	list_del_rcu(&range->list);
+	mutex_unlock(&io_range_mutex);
+	synchronize_rcu();
+}
+
+/**
+ * find_io_range_by_fwnode - find logical PIO range for given FW node
+ * @fwnode: FW node handle associated with logical PIO range
+ *
+ * Returns pointer to node on success, NULL otherwise.
+ *
+ * Traverse the io_range_list to find the registered node for @fwnode.
+ */
+struct logic_pio_hwaddr *find_io_range_by_fwnode(const struct fwnode_handle *fwnode)
+{
+	struct logic_pio_hwaddr *range, *found_range = NULL;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (range->fwnode == fwnode) {
+			found_range = range;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return found_range;
+}
+
+/* Return a registered range given an input PIO token */
+static struct logic_pio_hwaddr *find_io_range(unsigned long pio)
+{
+	struct logic_pio_hwaddr *range, *found_range = NULL;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (in_range(pio, range->io_start, range->size)) {
+			found_range = range;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!found_range)
+		pr_err("PIO entry token 0x%lx invalid\n", pio);
+
+	return found_range;
+}
+
+/**
+ * logic_pio_to_hwaddr - translate logical PIO to HW address
+ * @pio: logical PIO value
+ *
+ * Returns HW address if valid, ~0 otherwise.
+ *
+ * Translate the input logical PIO to the corresponding hardware address.
+ * The input PIO should be unique in the whole logical PIO space.
+ */
+resource_size_t logic_pio_to_hwaddr(unsigned long pio)
+{
+	struct logic_pio_hwaddr *range;
+
+	range = find_io_range(pio);
+	if (range)
+		return range->hw_start + pio - range->io_start;
+
+	return (resource_size_t)~0;
+}
+
+/**
+ * logic_pio_trans_hwaddr - translate HW address to logical PIO
+ * @fwnode: FW node reference for the host
+ * @addr: Host-relative HW address
+ * @size: size to translate
+ *
+ * Returns Logical PIO value if successful, ~0UL otherwise
+ */
+unsigned long logic_pio_trans_hwaddr(const struct fwnode_handle *fwnode,
+				     resource_size_t addr, resource_size_t size)
+{
+	struct logic_pio_hwaddr *range;
+
+	range = find_io_range_by_fwnode(fwnode);
+	if (!range || range->flags == LOGIC_PIO_CPU_MMIO) {
+		pr_err("IO range not found or invalid\n");
+		return ~0UL;
+	}
+	if (range->size < size) {
+		pr_err("resource size %pa cannot fit in IO range size %pa\n",
+		       &size, &range->size);
+		return ~0UL;
+	}
+	return addr - range->hw_start + range->io_start;
+}
+
+unsigned long logic_pio_trans_cpuaddr(resource_size_t addr)
+{
+	struct logic_pio_hwaddr *range;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(range, &io_range_list, list) {
+		if (range->flags != LOGIC_PIO_CPU_MMIO)
+			continue;
+		if (in_range(addr, range->hw_start, range->size)) {
+			unsigned long cpuaddr;
+
+			cpuaddr = addr - range->hw_start + range->io_start;
+
+			rcu_read_unlock();
+			return cpuaddr;
+		}
+	}
+	rcu_read_unlock();
+
+	pr_err("addr %pa not registered in io_range_list\n", &addr);
+
+	return ~0UL;
+}
+
+#if defined(CONFIG_INDIRECT_PIO) && defined(PCI_IOBASE)
+#define BUILD_LOGIC_IO(bwl, type)					\
+type logic_in##bwl(unsigned long addr)					\
+{									\
+	type ret = (type)~0;						\
+									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		ret = _in##bwl(addr);					\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) { \
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			ret = entry->ops->in(entry->hostdata,		\
+					addr, sizeof(type));		\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+	return ret;							\
+}									\
+									\
+void logic_out##bwl(type value, unsigned long addr)			\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		_out##bwl(value, addr);				\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->out(entry->hostdata,		\
+					addr, value, sizeof(type));	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+}									\
+									\
+void logic_ins##bwl(unsigned long addr, void *buffer,			\
+		    unsigned int count)					\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		reads##bwl(PCI_IOBASE + addr, buffer, count);		\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->ins(entry->hostdata,		\
+				addr, buffer, sizeof(type), count);	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+									\
+}									\
+									\
+void logic_outs##bwl(unsigned long addr, const void *buffer,		\
+		     unsigned int count)				\
+{									\
+	if (addr < MMIO_UPPER_LIMIT) {					\
+		writes##bwl(PCI_IOBASE + addr, buffer, count);		\
+	} else if (addr >= MMIO_UPPER_LIMIT && addr < IO_SPACE_LIMIT) {	\
+		struct logic_pio_hwaddr *entry = find_io_range(addr);	\
+									\
+		if (entry)						\
+			entry->ops->outs(entry->hostdata,		\
+				addr, buffer, sizeof(type), count);	\
+		else							\
+			WARN_ON_ONCE(1);				\
+	}								\
+}
+
+BUILD_LOGIC_IO(b, u8)
+EXPORT_SYMBOL(logic_inb);
+EXPORT_SYMBOL(logic_insb);
+EXPORT_SYMBOL(logic_outb);
+EXPORT_SYMBOL(logic_outsb);
+
+BUILD_LOGIC_IO(w, u16)
+EXPORT_SYMBOL(logic_inw);
+EXPORT_SYMBOL(logic_insw);
+EXPORT_SYMBOL(logic_outw);
+EXPORT_SYMBOL(logic_outsw);
+
+BUILD_LOGIC_IO(l, u32)
+EXPORT_SYMBOL(logic_inl);
+EXPORT_SYMBOL(logic_insl);
+EXPORT_SYMBOL(logic_outl);
+EXPORT_SYMBOL(logic_outsl);
+
+#endif /* CONFIG_INDIRECT_PIO && PCI_IOBASE */