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>

3 files changed, 163 insertions, 0 deletions

diff --git a/sound/soc/sof/xtensa/Kconfig b/sound/soc/sof/xtensa/Kconfig
new file mode 100644
index 000000000..defd6d3dc
--- /dev/null
+++ b/sound/soc/sof/xtensa/Kconfig
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config SND_SOC_SOF_XTENSA
+	tristate
diff --git a/sound/soc/sof/xtensa/Makefile b/sound/soc/sof/xtensa/Makefile
new file mode 100644
index 000000000..b9e6e8f5a
--- /dev/null
+++ b/sound/soc/sof/xtensa/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+
+snd-sof-xtensa-dsp-y := core.o
+
+obj-$(CONFIG_SND_SOC_SOF_XTENSA) += snd-sof-xtensa-dsp.o
diff --git a/sound/soc/sof/xtensa/core.c b/sound/soc/sof/xtensa/core.c
new file mode 100644
index 000000000..50623e65f
--- /dev/null
+++ b/sound/soc/sof/xtensa/core.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+//
+// This file is provided under a dual BSD/GPLv2 license.  When using or
+// redistributing this file, you may do so under either license.
+//
+// Copyright(c) 2018 Intel Corporation
+//
+// Author: Pan Xiuli <xiuli.pan@linux.intel.com>
+//
+
+#include <linux/module.h>
+#include <sound/sof.h>
+#include <sound/sof/xtensa.h>
+#include "../sof-priv.h"
+
+struct xtensa_exception_cause {
+	u32 id;
+	const char *msg;
+	const char *description;
+};
+
+/*
+ * From 4.4.1.5 table 4-64 Exception Causes of Xtensa
+ * Instruction Set Architecture (ISA) Reference Manual
+ */
+static const struct xtensa_exception_cause xtensa_exception_causes[] = {
+	{0, "IllegalInstructionCause", "Illegal instruction"},
+	{1, "SyscallCause", "SYSCALL instruction"},
+	{2, "InstructionFetchErrorCause",
+	"Processor internal physical address or data error during instruction fetch"},
+	{3, "LoadStoreErrorCause",
+	"Processor internal physical address or data error during load or store"},
+	{4, "Level1InterruptCause",
+	"Level-1 interrupt as indicated by set level-1 bits in the INTERRUPT register"},
+	{5, "AllocaCause",
+	"MOVSP instruction, if caller’s registers are not in the register file"},
+	{6, "IntegerDivideByZeroCause",
+	"QUOS, QUOU, REMS, or REMU divisor operand is zero"},
+	{8, "PrivilegedCause",
+	"Attempt to execute a privileged operation when CRING ? 0"},
+	{9, "LoadStoreAlignmentCause", "Load or store to an unaligned address"},
+	{12, "InstrPIFDataErrorCause",
+	"PIF data error during instruction fetch"},
+	{13, "LoadStorePIFDataErrorCause",
+	"Synchronous PIF data error during LoadStore access"},
+	{14, "InstrPIFAddrErrorCause",
+	"PIF address error during instruction fetch"},
+	{15, "LoadStorePIFAddrErrorCause",
+	"Synchronous PIF address error during LoadStore access"},
+	{16, "InstTLBMissCause", "Error during Instruction TLB refill"},
+	{17, "InstTLBMultiHitCause",
+	"Multiple instruction TLB entries matched"},
+	{18, "InstFetchPrivilegeCause",
+	"An instruction fetch referenced a virtual address at a ring level less than CRING"},
+	{20, "InstFetchProhibitedCause",
+	"An instruction fetch referenced a page mapped with an attribute that does not permit instruction fetch"},
+	{24, "LoadStoreTLBMissCause",
+	"Error during TLB refill for a load or store"},
+	{25, "LoadStoreTLBMultiHitCause",
+	"Multiple TLB entries matched for a load or store"},
+	{26, "LoadStorePrivilegeCause",
+	"A load or store referenced a virtual address at a ring level less than CRING"},
+	{28, "LoadProhibitedCause",
+	"A load referenced a page mapped with an attribute that does not permit loads"},
+	{32, "Coprocessor0Disabled",
+	"Coprocessor 0 instruction when cp0 disabled"},
+	{33, "Coprocessor1Disabled",
+	"Coprocessor 1 instruction when cp1 disabled"},
+	{34, "Coprocessor2Disabled",
+	"Coprocessor 2 instruction when cp2 disabled"},
+	{35, "Coprocessor3Disabled",
+	"Coprocessor 3 instruction when cp3 disabled"},
+	{36, "Coprocessor4Disabled",
+	"Coprocessor 4 instruction when cp4 disabled"},
+	{37, "Coprocessor5Disabled",
+	"Coprocessor 5 instruction when cp5 disabled"},
+	{38, "Coprocessor6Disabled",
+	"Coprocessor 6 instruction when cp6 disabled"},
+	{39, "Coprocessor7Disabled",
+	"Coprocessor 7 instruction when cp7 disabled"},
+};
+
+/* only need xtensa atm */
+static void xtensa_dsp_oops(struct snd_sof_dev *sdev, const char *level, void *oops)
+{
+	struct sof_ipc_dsp_oops_xtensa *xoops = oops;
+	int i;
+
+	dev_printk(level, sdev->dev, "error: DSP Firmware Oops\n");
+	for (i = 0; i < ARRAY_SIZE(xtensa_exception_causes); i++) {
+		if (xtensa_exception_causes[i].id == xoops->exccause) {
+			dev_printk(level, sdev->dev,
+				   "error: Exception Cause: %s, %s\n",
+				   xtensa_exception_causes[i].msg,
+				   xtensa_exception_causes[i].description);
+		}
+	}
+	dev_printk(level, sdev->dev,
+		   "EXCCAUSE 0x%8.8x EXCVADDR 0x%8.8x PS       0x%8.8x SAR     0x%8.8x\n",
+		   xoops->exccause, xoops->excvaddr, xoops->ps, xoops->sar);
+	dev_printk(level, sdev->dev,
+		   "EPC1     0x%8.8x EPC2     0x%8.8x EPC3     0x%8.8x EPC4    0x%8.8x",
+		   xoops->epc1, xoops->epc2, xoops->epc3, xoops->epc4);
+	dev_printk(level, sdev->dev,
+		   "EPC5     0x%8.8x EPC6     0x%8.8x EPC7     0x%8.8x DEPC    0x%8.8x",
+		   xoops->epc5, xoops->epc6, xoops->epc7, xoops->depc);
+	dev_printk(level, sdev->dev,
+		   "EPS2     0x%8.8x EPS3     0x%8.8x EPS4     0x%8.8x EPS5    0x%8.8x",
+		   xoops->eps2, xoops->eps3, xoops->eps4, xoops->eps5);
+	dev_printk(level, sdev->dev,
+		   "EPS6     0x%8.8x EPS7     0x%8.8x INTENABL 0x%8.8x INTERRU 0x%8.8x",
+		   xoops->eps6, xoops->eps7, xoops->intenable, xoops->interrupt);
+}
+
+static void xtensa_stack(struct snd_sof_dev *sdev, const char *level, void *oops,
+			 u32 *stack, u32 stack_words)
+{
+	struct sof_ipc_dsp_oops_xtensa *xoops = oops;
+	u32 stack_ptr = xoops->plat_hdr.stackptr;
+	/* 4 * 8chars + 3 ws + 1 terminating NUL */
+	unsigned char buf[4 * 8 + 3 + 1];
+	int i;
+
+	dev_printk(level, sdev->dev, "stack dump from 0x%8.8x\n", stack_ptr);
+
+	/*
+	 * example output:
+	 * 0x0049fbb0: 8000f2d0 0049fc00 6f6c6c61 00632e63
+	 */
+	for (i = 0; i < stack_words; i += 4) {
+		hex_dump_to_buffer(stack + i, 16, 16, 4,
+				   buf, sizeof(buf), false);
+		dev_printk(level, sdev->dev, "0x%08x: %s\n", stack_ptr + i * 4, buf);
+	}
+
+	if (!xoops->plat_hdr.numaregs)
+		return;
+
+	dev_printk(level, sdev->dev, "AR registers:\n");
+	/* the number of ar registers is a multiple of 4 */
+	for (i = 0; i < xoops->plat_hdr.numaregs; i += 4) {
+		hex_dump_to_buffer(xoops->ar + i, 16, 16, 4,
+				   buf, sizeof(buf), false);
+		dev_printk(level, sdev->dev, "%#x: %s\n", i * 4, buf);
+	}
+}
+
+const struct dsp_arch_ops sof_xtensa_arch_ops = {
+	.dsp_oops = xtensa_dsp_oops,
+	.dsp_stack = xtensa_stack,
+};
+EXPORT_SYMBOL_NS(sof_xtensa_arch_ops, "SND_SOC_SOF_XTENSA");
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_DESCRIPTION("SOF Xtensa DSP support");