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>

1 files changed, 232 insertions, 0 deletions

diff --git a/sound/soc/sof/ipc.c b/sound/soc/sof/ipc.c
new file mode 100644
index 000000000..e6d8894b8
--- /dev/null
+++ b/sound/soc/sof/ipc.c
@@ -0,0 +1,232 @@
+// 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: Liam Girdwood <liam.r.girdwood@linux.intel.com>
+//
+// Generic IPC layer that can work over MMIO and SPI/I2C. PHY layer provided
+// by platform driver code.
+//
+
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+#include "sof-priv.h"
+#include "sof-audio.h"
+#include "ops.h"
+
+/**
+ * sof_ipc_send_msg - generic function to prepare and send one IPC message
+ * @sdev:		pointer to SOF core device struct
+ * @msg_data:		pointer to a message to send
+ * @msg_bytes:		number of bytes in the message
+ * @reply_bytes:	number of bytes available for the reply.
+ *			The buffer for the reply data is not passed to this
+ *			function, the available size is an information for the
+ *			reply handling functions.
+ *
+ * On success the function returns 0, otherwise negative error number.
+ *
+ * Note: higher level sdev->ipc->tx_mutex must be held to make sure that
+ *	 transfers are synchronized.
+ */
+int sof_ipc_send_msg(struct snd_sof_dev *sdev, void *msg_data, size_t msg_bytes,
+		     size_t reply_bytes)
+{
+	struct snd_sof_ipc *ipc = sdev->ipc;
+	struct snd_sof_ipc_msg *msg;
+	int ret;
+
+	if (ipc->disable_ipc_tx || sdev->fw_state != SOF_FW_BOOT_COMPLETE)
+		return -ENODEV;
+
+	/*
+	 * The spin-lock is needed to protect message objects against other
+	 * atomic contexts.
+	 */
+	guard(spinlock_irq)(&sdev->ipc_lock);
+
+	/* initialise the message */
+	msg = &ipc->msg;
+
+	/* attach message data */
+	msg->msg_data = msg_data;
+	msg->msg_size = msg_bytes;
+
+	msg->reply_size = reply_bytes;
+	msg->reply_error = 0;
+
+	sdev->msg = msg;
+
+	ret = snd_sof_dsp_send_msg(sdev, msg);
+	/* Next reply that we receive will be related to this message */
+	if (!ret)
+		msg->ipc_complete = false;
+
+	return ret;
+}
+
+/* send IPC message from host to DSP */
+int sof_ipc_tx_message(struct snd_sof_ipc *ipc, void *msg_data, size_t msg_bytes,
+		       void *reply_data, size_t reply_bytes)
+{
+	if (msg_bytes > ipc->max_payload_size ||
+	    reply_bytes > ipc->max_payload_size)
+		return -ENOBUFS;
+
+	return ipc->ops->tx_msg(ipc->sdev, msg_data, msg_bytes, reply_data,
+				reply_bytes, false);
+}
+EXPORT_SYMBOL(sof_ipc_tx_message);
+
+/* IPC set or get data from host to DSP */
+int sof_ipc_set_get_data(struct snd_sof_ipc *ipc, void *msg_data,
+			 size_t msg_bytes, bool set)
+{
+	return ipc->ops->set_get_data(ipc->sdev, msg_data, msg_bytes, set);
+}
+EXPORT_SYMBOL(sof_ipc_set_get_data);
+
+/*
+ * send IPC message from host to DSP without modifying the DSP state.
+ * This will be used for IPC's that can be handled by the DSP
+ * even in a low-power D0 substate.
+ */
+int sof_ipc_tx_message_no_pm(struct snd_sof_ipc *ipc, void *msg_data, size_t msg_bytes,
+			     void *reply_data, size_t reply_bytes)
+{
+	if (msg_bytes > ipc->max_payload_size ||
+	    reply_bytes > ipc->max_payload_size)
+		return -ENOBUFS;
+
+	return ipc->ops->tx_msg(ipc->sdev, msg_data, msg_bytes, reply_data,
+				reply_bytes, true);
+}
+EXPORT_SYMBOL(sof_ipc_tx_message_no_pm);
+
+/* Generic helper function to retrieve the reply */
+void snd_sof_ipc_get_reply(struct snd_sof_dev *sdev)
+{
+	/*
+	 * Sometimes, there is unexpected reply ipc arriving. The reply
+	 * ipc belongs to none of the ipcs sent from driver.
+	 * In this case, the driver must ignore the ipc.
+	 */
+	if (!sdev->msg) {
+		dev_warn(sdev->dev, "unexpected ipc interrupt raised!\n");
+		return;
+	}
+
+	sdev->msg->reply_error = sdev->ipc->ops->get_reply(sdev);
+}
+EXPORT_SYMBOL(snd_sof_ipc_get_reply);
+
+/* handle reply message from DSP */
+void snd_sof_ipc_reply(struct snd_sof_dev *sdev, u32 msg_id)
+{
+	struct snd_sof_ipc_msg *msg = &sdev->ipc->msg;
+
+	if (msg->ipc_complete) {
+		dev_dbg(sdev->dev,
+			"no reply expected, received 0x%x, will be ignored",
+			msg_id);
+		return;
+	}
+
+	/* wake up and return the error if we have waiters on this message ? */
+	msg->ipc_complete = true;
+	wake_up(&msg->waitq);
+}
+EXPORT_SYMBOL(snd_sof_ipc_reply);
+
+struct snd_sof_ipc *snd_sof_ipc_init(struct snd_sof_dev *sdev)
+{
+	struct snd_sof_ipc *ipc;
+	struct snd_sof_ipc_msg *msg;
+	const struct sof_ipc_ops *ops;
+
+	ipc = devm_kzalloc(sdev->dev, sizeof(*ipc), GFP_KERNEL);
+	if (!ipc)
+		return NULL;
+
+	mutex_init(&ipc->tx_mutex);
+	ipc->sdev = sdev;
+	msg = &ipc->msg;
+
+	/* indicate that we aren't sending a message ATM */
+	msg->ipc_complete = true;
+
+	init_waitqueue_head(&msg->waitq);
+
+	switch (sdev->pdata->ipc_type) {
+#if defined(CONFIG_SND_SOC_SOF_IPC3)
+	case SOF_IPC_TYPE_3:
+		ops = &ipc3_ops;
+		break;
+#endif
+#if defined(CONFIG_SND_SOC_SOF_IPC4)
+	case SOF_IPC_TYPE_4:
+		ops = &ipc4_ops;
+		break;
+#endif
+	default:
+		dev_err(sdev->dev, "Not supported IPC version: %d\n",
+			sdev->pdata->ipc_type);
+		return NULL;
+	}
+
+	/* check for mandatory ops */
+	if (!ops->tx_msg || !ops->rx_msg || !ops->set_get_data || !ops->get_reply) {
+		dev_err(sdev->dev, "Missing IPC message handling ops\n");
+		return NULL;
+	}
+
+	if (!ops->fw_loader || !ops->fw_loader->validate ||
+	    !ops->fw_loader->parse_ext_manifest) {
+		dev_err(sdev->dev, "Missing IPC firmware loading ops\n");
+		return NULL;
+	}
+
+	if (!ops->pcm) {
+		dev_err(sdev->dev, "Missing IPC PCM ops\n");
+		return NULL;
+	}
+
+	if (!ops->tplg || !ops->tplg->widget || !ops->tplg->control) {
+		dev_err(sdev->dev, "Missing IPC topology ops\n");
+		return NULL;
+	}
+
+	if (ops->fw_tracing && (!ops->fw_tracing->init || !ops->fw_tracing->suspend ||
+				!ops->fw_tracing->resume)) {
+		dev_err(sdev->dev, "Missing firmware tracing ops\n");
+		return NULL;
+	}
+
+	if (ops->init && ops->init(sdev))
+		return NULL;
+
+	ipc->ops = ops;
+
+	return ipc;
+}
+EXPORT_SYMBOL(snd_sof_ipc_init);
+
+void snd_sof_ipc_free(struct snd_sof_dev *sdev)
+{
+	struct snd_sof_ipc *ipc = sdev->ipc;
+
+	if (!ipc)
+		return;
+
+	/* disable sending of ipc's */
+	scoped_guard(mutex, &ipc->tx_mutex)
+		ipc->disable_ipc_tx = true;
+
+	if (ipc->ops->exit)
+		ipc->ops->exit(sdev);
+}
+EXPORT_SYMBOL(snd_sof_ipc_free);