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, 244 insertions, 0 deletions

diff --git a/crypto/cmac.c b/crypto/cmac.c
new file mode 100644
index 000000000..83e58937f
--- /dev/null
+++ b/crypto/cmac.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * CMAC: Cipher Block Mode for Authentication
+ *
+ * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi>
+ *
+ * Based on work by:
+ *  Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com>
+ * Based on crypto/xcbc.c:
+ *  Copyright © 2006 USAGI/WIDE Project,
+ *   Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org>
+ */
+
+#include <crypto/internal/cipher.h>
+#include <crypto/internal/hash.h>
+#include <crypto/utils.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+/*
+ * +------------------------
+ * | <parent tfm>
+ * +------------------------
+ * | cmac_tfm_ctx
+ * +------------------------
+ * | consts (block size * 2)
+ * +------------------------
+ */
+struct cmac_tfm_ctx {
+	struct crypto_cipher *child;
+	__be64 consts[];
+};
+
+static int crypto_cmac_digest_setkey(struct crypto_shash *parent,
+				     const u8 *inkey, unsigned int keylen)
+{
+	struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent);
+	unsigned int bs = crypto_shash_blocksize(parent);
+	__be64 *consts = ctx->consts;
+	u64 _const[2];
+	int i, err = 0;
+	u8 msb_mask, gfmask;
+
+	err = crypto_cipher_setkey(ctx->child, inkey, keylen);
+	if (err)
+		return err;
+
+	/* encrypt the zero block */
+	memset(consts, 0, bs);
+	crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts);
+
+	switch (bs) {
+	case 16:
+		gfmask = 0x87;
+		_const[0] = be64_to_cpu(consts[1]);
+		_const[1] = be64_to_cpu(consts[0]);
+
+		/* gf(2^128) multiply zero-ciphertext with u and u^2 */
+		for (i = 0; i < 4; i += 2) {
+			msb_mask = ((s64)_const[1] >> 63) & gfmask;
+			_const[1] = (_const[1] << 1) | (_const[0] >> 63);
+			_const[0] = (_const[0] << 1) ^ msb_mask;
+
+			consts[i + 0] = cpu_to_be64(_const[1]);
+			consts[i + 1] = cpu_to_be64(_const[0]);
+		}
+
+		break;
+	case 8:
+		gfmask = 0x1B;
+		_const[0] = be64_to_cpu(consts[0]);
+
+		/* gf(2^64) multiply zero-ciphertext with u and u^2 */
+		for (i = 0; i < 2; i++) {
+			msb_mask = ((s64)_const[0] >> 63) & gfmask;
+			_const[0] = (_const[0] << 1) ^ msb_mask;
+
+			consts[i] = cpu_to_be64(_const[0]);
+		}
+
+		break;
+	}
+
+	return 0;
+}
+
+static int crypto_cmac_digest_init(struct shash_desc *pdesc)
+{
+	int bs = crypto_shash_blocksize(pdesc->tfm);
+	u8 *prev = shash_desc_ctx(pdesc);
+
+	memset(prev, 0, bs);
+	return 0;
+}
+
+static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p,
+				     unsigned int len)
+{
+	struct crypto_shash *parent = pdesc->tfm;
+	struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
+	struct crypto_cipher *tfm = tctx->child;
+	int bs = crypto_shash_blocksize(parent);
+	u8 *prev = shash_desc_ctx(pdesc);
+
+	do {
+		crypto_xor(prev, p, bs);
+		crypto_cipher_encrypt_one(tfm, prev, prev);
+		p += bs;
+		len -= bs;
+	} while (len >= bs);
+	return len;
+}
+
+static int crypto_cmac_digest_finup(struct shash_desc *pdesc, const u8 *src,
+				    unsigned int len, u8 *out)
+{
+	struct crypto_shash *parent = pdesc->tfm;
+	struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent);
+	struct crypto_cipher *tfm = tctx->child;
+	int bs = crypto_shash_blocksize(parent);
+	u8 *prev = shash_desc_ctx(pdesc);
+	unsigned int offset = 0;
+
+	crypto_xor(prev, src, len);
+	if (len != bs) {
+		prev[len] ^= 0x80;
+		offset += bs;
+	}
+	crypto_xor(prev, (const u8 *)tctx->consts + offset, bs);
+	crypto_cipher_encrypt_one(tfm, out, prev);
+	return 0;
+}
+
+static int cmac_init_tfm(struct crypto_shash *tfm)
+{
+	struct shash_instance *inst = shash_alg_instance(tfm);
+	struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
+	struct crypto_cipher_spawn *spawn;
+	struct crypto_cipher *cipher;
+
+	spawn = shash_instance_ctx(inst);
+	cipher = crypto_spawn_cipher(spawn);
+	if (IS_ERR(cipher))
+		return PTR_ERR(cipher);
+
+	ctx->child = cipher;
+
+	return 0;
+}
+
+static void cmac_exit_tfm(struct crypto_shash *tfm)
+{
+	struct cmac_tfm_ctx *ctx = crypto_shash_ctx(tfm);
+	crypto_free_cipher(ctx->child);
+}
+
+static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct shash_instance *inst;
+	struct crypto_cipher_spawn *spawn;
+	struct crypto_alg *alg;
+	u32 mask;
+	int err;
+
+	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
+	if (err)
+		return err;
+
+	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
+	if (!inst)
+		return -ENOMEM;
+	spawn = shash_instance_ctx(inst);
+
+	err = crypto_grab_cipher(spawn, shash_crypto_instance(inst),
+				 crypto_attr_alg_name(tb[1]), 0, mask);
+	if (err)
+		goto err_free_inst;
+	alg = crypto_spawn_cipher_alg(spawn);
+
+	switch (alg->cra_blocksize) {
+	case 16:
+	case 8:
+		break;
+	default:
+		err = -EINVAL;
+		goto err_free_inst;
+	}
+
+	err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
+	if (err)
+		goto err_free_inst;
+
+	inst->alg.base.cra_priority = alg->cra_priority;
+	inst->alg.base.cra_blocksize = alg->cra_blocksize;
+	inst->alg.base.cra_ctxsize = sizeof(struct cmac_tfm_ctx) +
+				     alg->cra_blocksize * 2;
+	inst->alg.base.cra_flags = CRYPTO_AHASH_ALG_BLOCK_ONLY |
+				   CRYPTO_AHASH_ALG_FINAL_NONZERO;
+
+	inst->alg.digestsize = alg->cra_blocksize;
+	inst->alg.descsize = alg->cra_blocksize;
+	inst->alg.init = crypto_cmac_digest_init;
+	inst->alg.update = crypto_cmac_digest_update;
+	inst->alg.finup = crypto_cmac_digest_finup;
+	inst->alg.setkey = crypto_cmac_digest_setkey;
+	inst->alg.init_tfm = cmac_init_tfm;
+	inst->alg.exit_tfm = cmac_exit_tfm;
+
+	inst->free = shash_free_singlespawn_instance;
+
+	err = shash_register_instance(tmpl, inst);
+	if (err) {
+err_free_inst:
+		shash_free_singlespawn_instance(inst);
+	}
+	return err;
+}
+
+static struct crypto_template crypto_cmac_tmpl = {
+	.name = "cmac",
+	.create = cmac_create,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_cmac_module_init(void)
+{
+	return crypto_register_template(&crypto_cmac_tmpl);
+}
+
+static void __exit crypto_cmac_module_exit(void)
+{
+	crypto_unregister_template(&crypto_cmac_tmpl);
+}
+
+module_init(crypto_cmac_module_init);
+module_exit(crypto_cmac_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("CMAC keyed hash algorithm");
+MODULE_ALIAS_CRYPTO("cmac");
+MODULE_IMPORT_NS("CRYPTO_INTERNAL");