sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 184 insertions, 0 deletions

diff --git a/drivers/firmware/trusted_foundations.c b/drivers/firmware/trusted_foundations.c
new file mode 100644
index 000000000..1389fa941
--- /dev/null
+++ b/drivers/firmware/trusted_foundations.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Trusted Foundations support for ARM CPUs
+ *
+ * Copyright (c) 2013, NVIDIA Corporation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/of.h>
+
+#include <linux/firmware/trusted_foundations.h>
+
+#include <asm/firmware.h>
+#include <asm/hardware/cache-l2x0.h>
+#include <asm/outercache.h>
+
+#define TF_CACHE_MAINT		0xfffff100
+
+#define TF_CACHE_ENABLE		1
+#define TF_CACHE_DISABLE	2
+#define TF_CACHE_REENABLE	4
+
+#define TF_SET_CPU_BOOT_ADDR_SMC 0xfffff200
+
+#define TF_CPU_PM		0xfffffffc
+#define TF_CPU_PM_S3		0xffffffe3
+#define TF_CPU_PM_S2		0xffffffe6
+#define TF_CPU_PM_S2_NO_MC_CLK	0xffffffe5
+#define TF_CPU_PM_S1		0xffffffe4
+#define TF_CPU_PM_S1_NOFLUSH_L2	0xffffffe7
+
+static unsigned long tf_idle_mode = TF_PM_MODE_NONE;
+static unsigned long cpu_boot_addr;
+
+static void tf_generic_smc(u32 type, u32 arg1, u32 arg2)
+{
+	register u32 r0 asm("r0") = type;
+	register u32 r1 asm("r1") = arg1;
+	register u32 r2 asm("r2") = arg2;
+
+	asm volatile(
+		".arch_extension	sec\n\t"
+		"stmfd	sp!, {r4 - r11}\n\t"
+		__asmeq("%0", "r0")
+		__asmeq("%1", "r1")
+		__asmeq("%2", "r2")
+		"mov	r3, #0\n\t"
+		"mov	r4, #0\n\t"
+		"smc	#0\n\t"
+		"ldmfd	sp!, {r4 - r11}\n\t"
+		:
+		: "r" (r0), "r" (r1), "r" (r2)
+		: "memory", "r3", "r12", "lr");
+}
+
+static int tf_set_cpu_boot_addr(int cpu, unsigned long boot_addr)
+{
+	cpu_boot_addr = boot_addr;
+	tf_generic_smc(TF_SET_CPU_BOOT_ADDR_SMC, cpu_boot_addr, 0);
+
+	return 0;
+}
+
+static int tf_prepare_idle(unsigned long mode)
+{
+	switch (mode) {
+	case TF_PM_MODE_LP0:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S3, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP1:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S2, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP1_NO_MC_CLK:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S2_NO_MC_CLK,
+			       cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP2:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S1, cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_LP2_NOFLUSH_L2:
+		tf_generic_smc(TF_CPU_PM, TF_CPU_PM_S1_NOFLUSH_L2,
+			       cpu_boot_addr);
+		break;
+
+	case TF_PM_MODE_NONE:
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	tf_idle_mode = mode;
+
+	return 0;
+}
+
+#ifdef CONFIG_CACHE_L2X0
+static void tf_cache_write_sec(unsigned long val, unsigned int reg)
+{
+	u32 enable_op, l2x0_way_mask = 0xff;
+
+	switch (reg) {
+	case L2X0_CTRL:
+		if (l2x0_saved_regs.aux_ctrl & L310_AUX_CTRL_ASSOCIATIVITY_16)
+			l2x0_way_mask = 0xffff;
+
+		switch (tf_idle_mode) {
+		case TF_PM_MODE_LP2:
+			enable_op = TF_CACHE_REENABLE;
+			break;
+
+		default:
+			enable_op = TF_CACHE_ENABLE;
+			break;
+		}
+
+		if (val == L2X0_CTRL_EN)
+			tf_generic_smc(TF_CACHE_MAINT, enable_op,
+				       l2x0_saved_regs.aux_ctrl);
+		else
+			tf_generic_smc(TF_CACHE_MAINT, TF_CACHE_DISABLE,
+				       l2x0_way_mask);
+		break;
+
+	default:
+		break;
+	}
+}
+
+static int tf_init_cache(void)
+{
+	outer_cache.write_sec = tf_cache_write_sec;
+
+	return 0;
+}
+#endif /* CONFIG_CACHE_L2X0 */
+
+static const struct firmware_ops trusted_foundations_ops = {
+	.set_cpu_boot_addr = tf_set_cpu_boot_addr,
+	.prepare_idle = tf_prepare_idle,
+#ifdef CONFIG_CACHE_L2X0
+	.l2x0_init = tf_init_cache,
+#endif
+};
+
+void register_trusted_foundations(struct trusted_foundations_platform_data *pd)
+{
+	/*
+	 * we are not using version information for now since currently
+	 * supported SMCs are compatible with all TF releases
+	 */
+	register_firmware_ops(&trusted_foundations_ops);
+}
+
+void of_register_trusted_foundations(void)
+{
+	struct device_node *node;
+	struct trusted_foundations_platform_data pdata;
+	int err;
+
+	node = of_find_compatible_node(NULL, NULL, "tlm,trusted-foundations");
+	if (!node)
+		return;
+
+	err = of_property_read_u32(node, "tlm,version-major",
+				   &pdata.version_major);
+	if (err != 0)
+		panic("Trusted Foundation: missing version-major property\n");
+	err = of_property_read_u32(node, "tlm,version-minor",
+				   &pdata.version_minor);
+	if (err != 0)
+		panic("Trusted Foundation: missing version-minor property\n");
+	register_trusted_foundations(&pdata);
+}
+
+bool trusted_foundations_registered(void)
+{
+	return firmware_ops == &trusted_foundations_ops;
+}