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, 381 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
new file mode 100644
index 000000000..b14ce5106
--- /dev/null
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Platform Security Processor (PSP) interface
+ *
+ * Copyright (C) 2016,2019 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <brijesh.singh@amd.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/irqreturn.h>
+#include <linux/mutex.h>
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+
+#include "sp-dev.h"
+#include "psp-dev.h"
+#include "sev-dev.h"
+#include "tee-dev.h"
+#include "sfs.h"
+#include "platform-access.h"
+#include "dbc.h"
+#include "hsti.h"
+
+struct psp_device *psp_master;
+
+#define PSP_C2PMSG_17_CMDRESP_CMD	GENMASK(19, 16)
+
+static int psp_mailbox_poll(const void __iomem *cmdresp_reg, unsigned int *cmdresp,
+			    unsigned int timeout_msecs)
+{
+	while (true) {
+		*cmdresp = ioread32(cmdresp_reg);
+		if (FIELD_GET(PSP_CMDRESP_RESP, *cmdresp))
+			return 0;
+
+		if (!timeout_msecs--)
+			break;
+
+		usleep_range(1000, 1100);
+	}
+
+	return -ETIMEDOUT;
+}
+
+int psp_mailbox_command(struct psp_device *psp, enum psp_cmd cmd, void *cmdbuff,
+			unsigned int timeout_msecs, unsigned int *cmdresp)
+{
+	void __iomem *cmdresp_reg, *cmdbuff_lo_reg, *cmdbuff_hi_reg;
+	int ret;
+
+	if (!psp || !psp->vdata || !psp->vdata->cmdresp_reg ||
+	    !psp->vdata->cmdbuff_addr_lo_reg || !psp->vdata->cmdbuff_addr_hi_reg)
+		return -ENODEV;
+
+	cmdresp_reg    = psp->io_regs + psp->vdata->cmdresp_reg;
+	cmdbuff_lo_reg = psp->io_regs + psp->vdata->cmdbuff_addr_lo_reg;
+	cmdbuff_hi_reg = psp->io_regs + psp->vdata->cmdbuff_addr_hi_reg;
+
+	mutex_lock(&psp->mailbox_mutex);
+
+	/* Ensure mailbox is ready for a command */
+	ret = -EBUSY;
+	if (psp_mailbox_poll(cmdresp_reg, cmdresp, 0))
+		goto unlock;
+
+	if (cmdbuff) {
+		iowrite32(lower_32_bits(__psp_pa(cmdbuff)), cmdbuff_lo_reg);
+		iowrite32(upper_32_bits(__psp_pa(cmdbuff)), cmdbuff_hi_reg);
+	}
+
+	*cmdresp = FIELD_PREP(PSP_C2PMSG_17_CMDRESP_CMD, cmd);
+	iowrite32(*cmdresp, cmdresp_reg);
+
+	ret = psp_mailbox_poll(cmdresp_reg, cmdresp, timeout_msecs);
+
+unlock:
+	mutex_unlock(&psp->mailbox_mutex);
+
+	return ret;
+}
+
+int psp_extended_mailbox_cmd(struct psp_device *psp, unsigned int timeout_msecs,
+			     struct psp_ext_request *req)
+{
+	unsigned int reg;
+	int ret;
+
+	print_hex_dump_debug("->psp ", DUMP_PREFIX_OFFSET, 16, 2, req,
+			     req->header.payload_size, false);
+
+	ret = psp_mailbox_command(psp, PSP_CMD_TEE_EXTENDED_CMD, (void *)req,
+				  timeout_msecs, &reg);
+	if (ret) {
+		return ret;
+	} else if (FIELD_GET(PSP_CMDRESP_STS, reg)) {
+		req->header.status = FIELD_GET(PSP_CMDRESP_STS, reg);
+		return -EIO;
+	}
+
+	print_hex_dump_debug("<-psp ", DUMP_PREFIX_OFFSET, 16, 2, req,
+			     req->header.payload_size, false);
+
+	return 0;
+}
+
+static struct psp_device *psp_alloc_struct(struct sp_device *sp)
+{
+	struct device *dev = sp->dev;
+	struct psp_device *psp;
+
+	psp = devm_kzalloc(dev, sizeof(*psp), GFP_KERNEL);
+	if (!psp)
+		return NULL;
+
+	psp->dev = dev;
+	psp->sp = sp;
+
+	snprintf(psp->name, sizeof(psp->name), "psp-%u", sp->ord);
+
+	return psp;
+}
+
+static irqreturn_t psp_irq_handler(int irq, void *data)
+{
+	struct psp_device *psp = data;
+	unsigned int status;
+
+	/* Read the interrupt status: */
+	status = ioread32(psp->io_regs + psp->vdata->intsts_reg);
+
+	/* Clear the interrupt status by writing the same value we read. */
+	iowrite32(status, psp->io_regs + psp->vdata->intsts_reg);
+
+	/* invoke subdevice interrupt handlers */
+	if (status) {
+		if (psp->sev_irq_handler)
+			psp->sev_irq_handler(irq, psp->sev_irq_data, status);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int psp_get_capability(struct psp_device *psp)
+{
+	unsigned int val = ioread32(psp->io_regs + psp->vdata->feature_reg);
+
+	/*
+	 * Check for a access to the registers.  If this read returns
+	 * 0xffffffff, it's likely that the system is running a broken
+	 * BIOS which disallows access to the device. Stop here and
+	 * fail the PSP initialization (but not the load, as the CCP
+	 * could get properly initialized).
+	 */
+	if (val == 0xffffffff) {
+		dev_notice(psp->dev, "psp: unable to access the device: you might be running a broken BIOS.\n");
+		return -ENODEV;
+	}
+	psp->capability.raw = val;
+
+	return 0;
+}
+
+static int psp_check_sev_support(struct psp_device *psp)
+{
+	/* Check if device supports SEV feature */
+	if (!psp->capability.sev) {
+		dev_dbg(psp->dev, "psp does not support SEV\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int psp_check_tee_support(struct psp_device *psp)
+{
+	/* Check if device supports TEE feature */
+	if (!psp->capability.tee) {
+		dev_dbg(psp->dev, "psp does not support TEE\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int psp_check_sfs_support(struct psp_device *psp)
+{
+	/* Check if device supports SFS feature */
+	if (!psp->capability.sfs) {
+		dev_dbg(psp->dev, "psp does not support SFS\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int psp_init(struct psp_device *psp)
+{
+	int ret;
+
+	if (!psp_check_sev_support(psp)) {
+		ret = sev_dev_init(psp);
+		if (ret)
+			return ret;
+	}
+
+	if (!psp_check_tee_support(psp)) {
+		ret = tee_dev_init(psp);
+		if (ret)
+			return ret;
+	}
+
+	if (!psp_check_sfs_support(psp)) {
+		ret = sfs_dev_init(psp);
+		if (ret)
+			return ret;
+	}
+
+	if (psp->vdata->platform_access) {
+		ret = platform_access_dev_init(psp);
+		if (ret)
+			return ret;
+	}
+
+	/* dbc must come after platform access as it tests the feature */
+	if (PSP_FEATURE(psp, DBC) ||
+	    psp->capability.dbc_thru_ext) {
+		ret = dbc_dev_init(psp);
+		if (ret)
+			return ret;
+	}
+
+	/* HSTI uses platform access on some systems. */
+	ret = psp_init_hsti(psp);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+int psp_dev_init(struct sp_device *sp)
+{
+	struct device *dev = sp->dev;
+	struct psp_device *psp;
+	int ret;
+
+	ret = -ENOMEM;
+	psp = psp_alloc_struct(sp);
+	if (!psp)
+		goto e_err;
+
+	sp->psp_data = psp;
+
+	psp->vdata = (struct psp_vdata *)sp->dev_vdata->psp_vdata;
+	if (!psp->vdata) {
+		ret = -ENODEV;
+		dev_err(dev, "missing driver data\n");
+		goto e_err;
+	}
+
+	psp->io_regs = sp->io_map;
+	mutex_init(&psp->mailbox_mutex);
+
+	ret = psp_get_capability(psp);
+	if (ret)
+		goto e_disable;
+
+	/* Disable and clear interrupts until ready */
+	iowrite32(0, psp->io_regs + psp->vdata->inten_reg);
+	iowrite32(-1, psp->io_regs + psp->vdata->intsts_reg);
+
+	/* Request an irq */
+	ret = sp_request_psp_irq(psp->sp, psp_irq_handler, psp->name, psp);
+	if (ret) {
+		dev_err(dev, "psp: unable to allocate an IRQ\n");
+		goto e_err;
+	}
+
+	/* master device must be set for platform access */
+	if (psp->sp->set_psp_master_device)
+		psp->sp->set_psp_master_device(psp->sp);
+
+	ret = psp_init(psp);
+	if (ret)
+		goto e_irq;
+
+	/* Enable interrupt */
+	iowrite32(-1, psp->io_regs + psp->vdata->inten_reg);
+
+	dev_notice(dev, "psp enabled\n");
+
+	return 0;
+
+e_irq:
+	if (sp->clear_psp_master_device)
+		sp->clear_psp_master_device(sp);
+
+	sp_free_psp_irq(psp->sp, psp);
+e_err:
+	sp->psp_data = NULL;
+
+	dev_notice(dev, "psp initialization failed\n");
+
+	return ret;
+
+e_disable:
+	sp->psp_data = NULL;
+
+	return ret;
+}
+
+void psp_dev_destroy(struct sp_device *sp)
+{
+	struct psp_device *psp = sp->psp_data;
+
+	if (!psp)
+		return;
+
+	dbc_dev_destroy(psp);
+
+	platform_access_dev_destroy(psp);
+
+	sfs_dev_destroy(psp);
+
+	tee_dev_destroy(psp);
+
+	sev_dev_destroy(psp);
+
+	sp_free_psp_irq(sp, psp);
+
+	if (sp->clear_psp_master_device)
+		sp->clear_psp_master_device(sp);
+}
+
+void psp_set_sev_irq_handler(struct psp_device *psp, psp_irq_handler_t handler,
+			     void *data)
+{
+	psp->sev_irq_data = data;
+	psp->sev_irq_handler = handler;
+}
+
+void psp_clear_sev_irq_handler(struct psp_device *psp)
+{
+	psp_set_sev_irq_handler(psp, NULL, NULL);
+}
+
+struct psp_device *psp_get_master_device(void)
+{
+	struct sp_device *sp = sp_get_psp_master_device();
+
+	return sp ? sp->psp_data : NULL;
+}
+
+int psp_restore(struct sp_device *sp)
+{
+	struct psp_device *psp = sp->psp_data;
+	int ret = 0;
+
+	if (psp->tee_data)
+		ret = tee_restore(psp);
+
+	return ret;
+}
+
+void psp_pci_init(void)
+{
+	psp_master = psp_get_master_device();
+
+	if (!psp_master)
+		return;
+
+	sev_pci_init();
+}
+
+void psp_pci_exit(void)
+{
+	if (!psp_master)
+		return;
+
+	sev_pci_exit();
+}