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, 377 insertions, 0 deletions

diff --git a/arch/powerpc/boot/devtree.c b/arch/powerpc/boot/devtree.c
new file mode 100644
index 000000000..58fbcfcc9
--- /dev/null
+++ b/arch/powerpc/boot/devtree.c
@@ -0,0 +1,377 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * devtree.c - convenience functions for device tree manipulation
+ * Copyright 2007 David Gibson, IBM Corporation.
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ *
+ * Authors: David Gibson <david@gibson.dropbear.id.au>
+ *	    Scott Wood <scottwood@freescale.com>
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "string.h"
+#include "stdio.h"
+#include "ops.h"
+#include "of.h"
+
+void dt_fixup_memory(u64 start, u64 size)
+{
+	void *root, *memory;
+	int naddr, nsize, i;
+	u32 memreg[4];
+
+	root = finddevice("/");
+	if (getprop(root, "#address-cells", &naddr, sizeof(naddr)) < 0)
+		naddr = 2;
+	else
+		naddr = be32_to_cpu(naddr);
+	if (naddr < 1 || naddr > 2)
+		fatal("Can't cope with #address-cells == %d in /\n\r", naddr);
+
+	if (getprop(root, "#size-cells", &nsize, sizeof(nsize)) < 0)
+		nsize = 1;
+	else
+		nsize = be32_to_cpu(nsize);
+	if (nsize < 1 || nsize > 2)
+		fatal("Can't cope with #size-cells == %d in /\n\r", nsize);
+
+	i = 0;
+	if (naddr == 2)
+		memreg[i++] = cpu_to_be32(start >> 32);
+	memreg[i++] = cpu_to_be32(start & 0xffffffff);
+	if (nsize == 2)
+		memreg[i++] = cpu_to_be32(size >> 32);
+	memreg[i++] = cpu_to_be32(size & 0xffffffff);
+
+	memory = finddevice("/memory");
+	if (! memory) {
+		memory = create_node(NULL, "memory");
+		setprop_str(memory, "device_type", "memory");
+	}
+
+	printf("Memory <- <0x%x", be32_to_cpu(memreg[0]));
+	for (i = 1; i < (naddr + nsize); i++)
+		printf(" 0x%x", be32_to_cpu(memreg[i]));
+	printf("> (%ldMB)\n\r", (unsigned long)(size >> 20));
+
+	setprop(memory, "reg", memreg, (naddr + nsize)*sizeof(u32));
+}
+
+#define MHZ(x)	((x + 500000) / 1000000)
+
+void dt_fixup_cpu_clocks(u32 cpu, u32 tb, u32 bus)
+{
+	void *devp = NULL;
+
+	printf("CPU clock-frequency <- 0x%x (%dMHz)\n\r", cpu, MHZ(cpu));
+	printf("CPU timebase-frequency <- 0x%x (%dMHz)\n\r", tb, MHZ(tb));
+	if (bus > 0)
+		printf("CPU bus-frequency <- 0x%x (%dMHz)\n\r", bus, MHZ(bus));
+
+	while ((devp = find_node_by_devtype(devp, "cpu"))) {
+		setprop_val(devp, "clock-frequency", cpu_to_be32(cpu));
+		setprop_val(devp, "timebase-frequency", cpu_to_be32(tb));
+		if (bus > 0)
+			setprop_val(devp, "bus-frequency", cpu_to_be32(bus));
+	}
+
+	timebase_period_ns = 1000000000 / tb;
+}
+
+void dt_fixup_clock(const char *path, u32 freq)
+{
+	void *devp = finddevice(path);
+
+	if (devp) {
+		printf("%s: clock-frequency <- %x (%dMHz)\n\r", path, freq, MHZ(freq));
+		setprop_val(devp, "clock-frequency", cpu_to_be32(freq));
+	}
+}
+
+void dt_fixup_mac_address_by_alias(const char *alias, const u8 *addr)
+{
+	void *devp = find_node_by_alias(alias);
+
+	if (devp) {
+		printf("%s: local-mac-address <-"
+		       " %02x:%02x:%02x:%02x:%02x:%02x\n\r", alias,
+		       addr[0], addr[1], addr[2],
+		       addr[3], addr[4], addr[5]);
+
+		setprop(devp, "local-mac-address", addr, 6);
+	}
+}
+
+void dt_fixup_mac_address(u32 index, const u8 *addr)
+{
+	void *devp = find_node_by_prop_value(NULL, "linux,network-index",
+	                                     (void*)&index, sizeof(index));
+
+	if (devp) {
+		printf("ENET%d: local-mac-address <-"
+		       " %02x:%02x:%02x:%02x:%02x:%02x\n\r", index,
+		       addr[0], addr[1], addr[2],
+		       addr[3], addr[4], addr[5]);
+
+		setprop(devp, "local-mac-address", addr, 6);
+	}
+}
+
+void __dt_fixup_mac_addresses(u32 startindex, ...)
+{
+	va_list ap;
+	u32 index = startindex;
+	const u8 *addr;
+
+	va_start(ap, startindex);
+
+	while ((addr = va_arg(ap, const u8 *)))
+		dt_fixup_mac_address(index++, addr);
+
+	va_end(ap);
+}
+
+#define MAX_ADDR_CELLS 4
+
+void dt_get_reg_format(void *node, u32 *naddr, u32 *nsize)
+{
+	if (getprop(node, "#address-cells", naddr, 4) != 4)
+		*naddr = 2;
+	else
+		*naddr = be32_to_cpu(*naddr);
+	if (getprop(node, "#size-cells", nsize, 4) != 4)
+		*nsize = 1;
+	else
+		*nsize = be32_to_cpu(*nsize);
+}
+
+static void copy_val(u32 *dest, u32 *src, int naddr)
+{
+	int pad = MAX_ADDR_CELLS - naddr;
+
+	memset(dest, 0, pad * 4);
+	memcpy(dest + pad, src, naddr * 4);
+}
+
+static int sub_reg(u32 *reg, u32 *sub)
+{
+	int i, borrow = 0;
+
+	for (i = MAX_ADDR_CELLS - 1; i >= 0; i--) {
+		int prev_borrow = borrow;
+		borrow = reg[i] < sub[i] + prev_borrow;
+		reg[i] -= sub[i] + prev_borrow;
+	}
+
+	return !borrow;
+}
+
+static int add_reg(u32 *reg, u32 *add, int naddr)
+{
+	int i, carry = 0;
+
+	for (i = MAX_ADDR_CELLS - 1; i >= MAX_ADDR_CELLS - naddr; i--) {
+		u64 tmp = (u64)be32_to_cpu(reg[i]) + be32_to_cpu(add[i]) + carry;
+		carry = tmp >> 32;
+		reg[i] = cpu_to_be32((u32)tmp);
+	}
+
+	return !carry;
+}
+
+/* It is assumed that if the first byte of reg fits in a
+ * range, then the whole reg block fits.
+ */
+static int compare_reg(u32 *reg, u32 *range, u32 *rangesize)
+{
+	int i;
+	u32 end;
+
+	for (i = 0; i < MAX_ADDR_CELLS; i++) {
+		if (be32_to_cpu(reg[i]) < be32_to_cpu(range[i]))
+			return 0;
+		if (be32_to_cpu(reg[i]) > be32_to_cpu(range[i]))
+			break;
+	}
+
+	for (i = 0; i < MAX_ADDR_CELLS; i++) {
+		end = be32_to_cpu(range[i]) + be32_to_cpu(rangesize[i]);
+
+		if (be32_to_cpu(reg[i]) < end)
+			break;
+		if (be32_to_cpu(reg[i]) > end)
+			return 0;
+	}
+
+	return reg[i] != end;
+}
+
+/* reg must be MAX_ADDR_CELLS */
+static int find_range(u32 *reg, u32 *ranges, int nregaddr,
+                      int naddr, int nsize, int buflen)
+{
+	int nrange = nregaddr + naddr + nsize;
+	int i;
+
+	for (i = 0; i + nrange <= buflen; i += nrange) {
+		u32 range_addr[MAX_ADDR_CELLS];
+		u32 range_size[MAX_ADDR_CELLS];
+
+		copy_val(range_addr, ranges + i, nregaddr);
+		copy_val(range_size, ranges + i + nregaddr + naddr, nsize);
+
+		if (compare_reg(reg, range_addr, range_size))
+			return i;
+	}
+
+	return -1;
+}
+
+/* Currently only generic buses without special encodings are supported.
+ * In particular, PCI is not supported.  Also, only the beginning of the
+ * reg block is tracked; size is ignored except in ranges.
+ */
+static u32 prop_buf[MAX_PROP_LEN / 4];
+
+static int dt_xlate(void *node, int res, int reglen, unsigned long *addr,
+		unsigned long *size)
+{
+	u32 last_addr[MAX_ADDR_CELLS];
+	u32 this_addr[MAX_ADDR_CELLS];
+	void *parent;
+	u64 ret_addr, ret_size;
+	u32 naddr, nsize, prev_naddr, prev_nsize;
+	int buflen, offset;
+
+	parent = get_parent(node);
+	if (!parent)
+		return 0;
+
+	dt_get_reg_format(parent, &naddr, &nsize);
+	if (nsize > 2)
+		return 0;
+
+	offset = (naddr + nsize) * res;
+
+	if (reglen < offset + naddr + nsize ||
+	    MAX_PROP_LEN < (offset + naddr + nsize) * 4)
+		return 0;
+
+	copy_val(last_addr, prop_buf + offset, naddr);
+
+	ret_size = be32_to_cpu(prop_buf[offset + naddr]);
+	if (nsize == 2) {
+		ret_size <<= 32;
+		ret_size |= be32_to_cpu(prop_buf[offset + naddr + 1]);
+	}
+
+	for (;;) {
+		prev_naddr = naddr;
+		prev_nsize = nsize;
+		node = parent;
+
+		parent = get_parent(node);
+		if (!parent)
+			break;
+
+		dt_get_reg_format(parent, &naddr, &nsize);
+
+		buflen = getprop(node, "ranges", prop_buf,
+				sizeof(prop_buf));
+		if (buflen == 0)
+			continue;
+		if (buflen < 0 || buflen > sizeof(prop_buf))
+			return 0;
+
+		offset = find_range(last_addr, prop_buf, prev_naddr,
+		                    naddr, prev_nsize, buflen / 4);
+		if (offset < 0)
+			return 0;
+
+		copy_val(this_addr, prop_buf + offset, prev_naddr);
+
+		if (!sub_reg(last_addr, this_addr))
+			return 0;
+
+		copy_val(this_addr, prop_buf + offset + prev_naddr, naddr);
+
+		if (!add_reg(last_addr, this_addr, naddr))
+			return 0;
+	}
+
+	if (naddr > 2)
+		return 0;
+
+	ret_addr = ((u64)be32_to_cpu(last_addr[2]) << 32) | be32_to_cpu(last_addr[3]);
+	if (sizeof(void *) == 4 &&
+	    (ret_addr >= 0x100000000ULL || ret_size > 0x100000000ULL ||
+	     ret_addr + ret_size > 0x100000000ULL))
+		return 0;
+
+	*addr = ret_addr;
+	if (size)
+		*size = ret_size;
+
+	return 1;
+}
+
+int dt_xlate_reg(void *node, int res, unsigned long *addr, unsigned long *size)
+{
+	int reglen;
+
+	reglen = getprop(node, "reg", prop_buf, sizeof(prop_buf)) / 4;
+	return dt_xlate(node, res, reglen, addr, size);
+}
+
+int dt_xlate_addr(void *node, u32 *buf, int buflen, unsigned long *xlated_addr)
+{
+
+	if (buflen > sizeof(prop_buf))
+		return 0;
+
+	memcpy(prop_buf, buf, buflen);
+	return dt_xlate(node, 0, buflen / 4, xlated_addr, NULL);
+}
+
+int dt_is_compatible(void *node, const char *compat)
+{
+	char *buf = (char *)prop_buf;
+	int len, pos;
+
+	len = getprop(node, "compatible", buf, MAX_PROP_LEN);
+	if (len < 0)
+		return 0;
+
+	for (pos = 0; pos < len; pos++) {
+		if (!strcmp(buf + pos, compat))
+			return 1;
+
+		pos += strnlen(&buf[pos], len - pos);
+	}
+
+	return 0;
+}
+
+int dt_get_virtual_reg(void *node, void **addr, int nres)
+{
+	unsigned long xaddr;
+	int n, i;
+
+	n = getprop(node, "virtual-reg", addr, nres * 4);
+	if (n > 0) {
+		for (i = 0; i < n/4; i ++)
+			((u32 *)addr)[i] = be32_to_cpu(((u32 *)addr)[i]);
+		return n / 4;
+	}
+
+	for (n = 0; n < nres; n++) {
+		if (!dt_xlate_reg(node, n, &xaddr, NULL))
+			break;
+
+		addr[n] = (void *)xaddr;
+	}
+
+	return n;
+}
+