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, 56 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/Kconfig b/drivers/crypto/ccp/Kconfig
new file mode 100644
index 000000000..f16a0f611
--- /dev/null
+++ b/drivers/crypto/ccp/Kconfig
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config CRYPTO_DEV_CCP_DD
+	tristate "Secure Processor device driver"
+	depends on CPU_SUP_AMD || ARM64
+	default m
+	help
+	  Provides AMD Secure Processor device driver.
+	  If you choose 'M' here, this module will be called ccp.
+
+config CRYPTO_DEV_SP_CCP
+	bool "Cryptographic Coprocessor device"
+	default y
+	depends on CRYPTO_DEV_CCP_DD && DMADEVICES
+	select HW_RANDOM
+	select DMA_ENGINE
+	select CRYPTO_SHA1
+	select CRYPTO_SHA256
+	help
+	  Provides the support for AMD Cryptographic Coprocessor (CCP) device
+	  which can be used to offload encryption operations such as SHA, AES
+	  and more.
+
+config CRYPTO_DEV_CCP_CRYPTO
+	tristate "Encryption and hashing offload support"
+	default m
+	depends on CRYPTO_DEV_CCP_DD
+	depends on CRYPTO_DEV_SP_CCP
+	select CRYPTO_HASH
+	select CRYPTO_SKCIPHER
+	select CRYPTO_AUTHENC
+	select CRYPTO_RSA
+	select CRYPTO_LIB_AES
+	help
+	  Support for using the cryptographic API with the AMD Cryptographic
+	  Coprocessor. This module supports offload of SHA and AES algorithms.
+	  If you choose 'M' here, this module will be called ccp_crypto.
+
+config CRYPTO_DEV_SP_PSP
+	bool "Platform Security Processor (PSP) device"
+	default y
+	depends on CRYPTO_DEV_CCP_DD && X86_64 && AMD_IOMMU
+	select PCI_TSM if PCI
+	help
+	 Provide support for the AMD Platform Security Processor (PSP).
+	 The PSP is a dedicated processor that provides support for key
+	 management commands in Secure Encrypted Virtualization (SEV) mode,
+	 along with software-based Trusted Execution Environment (TEE) to
+	 enable third-party trusted applications.
+
+config CRYPTO_DEV_CCP_DEBUGFS
+	bool "Enable CCP Internals in DebugFS"
+	default n
+	depends on CRYPTO_DEV_SP_CCP
+	help
+	  Expose CCP device information such as operation statistics, feature
+	  information, and descriptor queue contents.