virt: acrn: Introduce I/O request management

An I/O request of a User VM, which is constructed by the hypervisor, is
distributed by the ACRN Hypervisor Service Module to an I/O client
corresponding to the address range of the I/O request.

For each User VM, there is a shared 4-KByte memory region used for I/O
requests communication between the hypervisor and Service VM. An I/O
request is a 256-byte structure buffer, which is 'struct
acrn_io_request', that is filled by an I/O handler of the hypervisor
when a trapped I/O access happens in a User VM. ACRN userspace in the
Service VM first allocates a 4-KByte page and passes the GPA (Guest
Physical Address) of the buffer to the hypervisor. The buffer is used as
an array of 16 I/O request slots with each I/O request slot being 256
bytes. This array is indexed by vCPU ID.

An I/O client, which is 'struct acrn_ioreq_client', is responsible for
handling User VM I/O requests whose accessed GPA falls in a certain
range. Multiple I/O clients can be associated with each User VM. There
is a special client associated with each User VM, called the default
client, that handles all I/O requests that do not fit into the range of
any other I/O clients. The ACRN userspace acts as the default client for
each User VM.

The state transitions of a ACRN I/O request are as follows.

   FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...

FREE: this I/O request slot is empty
PENDING: a valid I/O request is pending in this slot
PROCESSING: the I/O request is being processed
COMPLETE: the I/O request has been processed

An I/O request in COMPLETE or FREE state is owned by the hypervisor. HSM
and ACRN userspace are in charge of processing the others.

The processing flow of I/O requests are listed as following:

a) The I/O handler of the hypervisor will fill an I/O request with
   PENDING state when a trapped I/O access happens in a User VM.
b) The hypervisor makes an upcall, which is a notification interrupt, to
   the Service VM.
c) The upcall handler schedules a worker to dispatch I/O requests.
d) The worker looks for the PENDING I/O requests, assigns them to
   different registered clients based on the address of the I/O accesses,
   updates their state to PROCESSING, and notifies the corresponding
   client to handle.
e) The notified client handles the assigned I/O requests.
f) The HSM updates I/O requests states to COMPLETE and notifies the
   hypervisor of the completion via hypercalls.

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Yu Wang <yu1.wang@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20210207031040.49576-10-shuo.a.liu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 521 insertions, 0 deletions

diff --git a/drivers/virt/acrn/ioreq.c b/drivers/virt/acrn/ioreq.c
new file mode 100644
index 000000000000..51cb41ef7c72
--- /dev/null
+++ b/drivers/virt/acrn/ioreq.c
@@ -0,0 +1,521 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACRN_HSM: Handle I/O requests
+ *
+ * Copyright (C) 2020 Intel Corporation. All rights reserved.
+ *
+ * Authors:
+ *	Jason Chen CJ <jason.cj.chen@intel.com>
+ *	Fengwei Yin <fengwei.yin@intel.com>
+ */
+
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kthread.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+
+#include <asm/acrn.h>
+
+#include "acrn_drv.h"
+
+static void ioreq_pause(void);
+static void ioreq_resume(void);
+
+static void ioreq_dispatcher(struct work_struct *work);
+static struct workqueue_struct *ioreq_wq;
+static DECLARE_WORK(ioreq_work, ioreq_dispatcher);
+
+static inline bool has_pending_request(struct acrn_ioreq_client *client)
+{
+	return !bitmap_empty(client->ioreqs_map, ACRN_IO_REQUEST_MAX);
+}
+
+static inline bool is_destroying(struct acrn_ioreq_client *client)
+{
+	return test_bit(ACRN_IOREQ_CLIENT_DESTROYING, &client->flags);
+}
+
+static int ioreq_complete_request(struct acrn_vm *vm, u16 vcpu,
+				  struct acrn_io_request *acrn_req)
+{
+	bool polling_mode;
+	int ret = 0;
+
+	polling_mode = acrn_req->completion_polling;
+	/* Add barrier() to make sure the writes are done before completion */
+	smp_store_release(&acrn_req->processed, ACRN_IOREQ_STATE_COMPLETE);
+
+	/*
+	 * To fulfill the requirement of real-time in several industry
+	 * scenarios, like automotive, ACRN can run under the partition mode,
+	 * in which User VMs and Service VM are bound to dedicated CPU cores.
+	 * Polling mode of handling the I/O request is introduced to achieve a
+	 * faster I/O request handling. In polling mode, the hypervisor polls
+	 * I/O request's completion. Once an I/O request is marked as
+	 * ACRN_IOREQ_STATE_COMPLETE, hypervisor resumes from the polling point
+	 * to continue the I/O request flow. Thus, the completion notification
+	 * from HSM of I/O request is not needed.  Please note,
+	 * completion_polling needs to be read before the I/O request being
+	 * marked as ACRN_IOREQ_STATE_COMPLETE to avoid racing with the
+	 * hypervisor.
+	 */
+	if (!polling_mode) {
+		ret = hcall_notify_req_finish(vm->vmid, vcpu);
+		if (ret < 0)
+			dev_err(acrn_dev.this_device,
+				"Notify I/O request finished failed!\n");
+	}
+
+	return ret;
+}
+
+static int acrn_ioreq_complete_request(struct acrn_ioreq_client *client,
+				       u16 vcpu,
+				       struct acrn_io_request *acrn_req)
+{
+	int ret;
+
+	if (vcpu >= client->vm->vcpu_num)
+		return -EINVAL;
+
+	clear_bit(vcpu, client->ioreqs_map);
+	if (!acrn_req) {
+		acrn_req = (struct acrn_io_request *)client->vm->ioreq_buf;
+		acrn_req += vcpu;
+	}
+
+	ret = ioreq_complete_request(client->vm, vcpu, acrn_req);
+
+	return ret;
+}
+
+int acrn_ioreq_request_default_complete(struct acrn_vm *vm, u16 vcpu)
+{
+	int ret = 0;
+
+	spin_lock_bh(&vm->ioreq_clients_lock);
+	if (vm->default_client)
+		ret = acrn_ioreq_complete_request(vm->default_client,
+						  vcpu, NULL);
+	spin_unlock_bh(&vm->ioreq_clients_lock);
+
+	return ret;
+}
+
+/*
+ * ioreq_task() is the execution entity of handler thread of an I/O client.
+ * The handler callback of the I/O client is called within the handler thread.
+ */
+static int ioreq_task(void *data)
+{
+	struct acrn_ioreq_client *client = data;
+	struct acrn_io_request *req;
+	unsigned long *ioreqs_map;
+	int vcpu, ret;
+
+	/*
+	 * Lockless access to ioreqs_map is safe, because
+	 * 1) set_bit() and clear_bit() are atomic operations.
+	 * 2) I/O requests arrives serialized. The access flow of ioreqs_map is:
+	 *	set_bit() - in ioreq_work handler
+	 *	Handler callback handles corresponding I/O request
+	 *	clear_bit() - in handler thread (include ACRN userspace)
+	 *	Mark corresponding I/O request completed
+	 *	Loop again if a new I/O request occurs
+	 */
+	ioreqs_map = client->ioreqs_map;
+	while (!kthread_should_stop()) {
+		acrn_ioreq_client_wait(client);
+		while (has_pending_request(client)) {
+			vcpu = find_first_bit(ioreqs_map, client->vm->vcpu_num);
+			req = client->vm->ioreq_buf->req_slot + vcpu;
+			ret = client->handler(client, req);
+			if (ret < 0) {
+				dev_err(acrn_dev.this_device,
+					"IO handle failure: %d\n", ret);
+				break;
+			}
+			acrn_ioreq_complete_request(client, vcpu, req);
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * For the non-default I/O clients, give them chance to complete the current
+ * I/O requests if there are any. For the default I/O client, it is safe to
+ * clear all pending I/O requests because the clearing request is from ACRN
+ * userspace.
+ */
+void acrn_ioreq_request_clear(struct acrn_vm *vm)
+{
+	struct acrn_ioreq_client *client;
+	bool has_pending = false;
+	unsigned long vcpu;
+	int retry = 10;
+
+	/*
+	 * IO requests of this VM will be completed directly in
+	 * acrn_ioreq_dispatch if ACRN_VM_FLAG_CLEARING_IOREQ flag is set.
+	 */
+	set_bit(ACRN_VM_FLAG_CLEARING_IOREQ, &vm->flags);
+
+	/*
+	 * acrn_ioreq_request_clear is only called in VM reset case. Simply
+	 * wait 100ms in total for the IO requests' completion.
+	 */
+	do {
+		spin_lock_bh(&vm->ioreq_clients_lock);
+		list_for_each_entry(client, &vm->ioreq_clients, list) {
+			has_pending = has_pending_request(client);
+			if (has_pending)
+				break;
+		}
+		spin_unlock_bh(&vm->ioreq_clients_lock);
+
+		if (has_pending)
+			schedule_timeout_interruptible(HZ / 100);
+	} while (has_pending && --retry > 0);
+	if (retry == 0)
+		dev_warn(acrn_dev.this_device,
+			 "%s cannot flush pending request!\n", client->name);
+
+	/* Clear all ioreqs belonging to the default client */
+	spin_lock_bh(&vm->ioreq_clients_lock);
+	client = vm->default_client;
+	if (client) {
+		vcpu = find_next_bit(client->ioreqs_map,
+				     ACRN_IO_REQUEST_MAX, 0);
+		while (vcpu < ACRN_IO_REQUEST_MAX) {
+			acrn_ioreq_complete_request(client, vcpu, NULL);
+			vcpu = find_next_bit(client->ioreqs_map,
+					     ACRN_IO_REQUEST_MAX, vcpu + 1);
+		}
+	}
+	spin_unlock_bh(&vm->ioreq_clients_lock);
+
+	/* Clear ACRN_VM_FLAG_CLEARING_IOREQ flag after the clearing */
+	clear_bit(ACRN_VM_FLAG_CLEARING_IOREQ, &vm->flags);
+}
+
+int acrn_ioreq_client_wait(struct acrn_ioreq_client *client)
+{
+	if (client->is_default) {
+		/*
+		 * In the default client, a user space thread waits on the
+		 * waitqueue. The is_destroying() check is used to notify user
+		 * space the client is going to be destroyed.
+		 */
+		wait_event_interruptible(client->wq,
+					 has_pending_request(client) ||
+					 is_destroying(client));
+		if (is_destroying(client))
+			return -ENODEV;
+	} else {
+		wait_event_interruptible(client->wq,
+					 has_pending_request(client) ||
+					 kthread_should_stop());
+	}
+
+	return 0;
+}
+
+static bool in_range(struct acrn_ioreq_range *range,
+		     struct acrn_io_request *req)
+{
+	bool ret = false;
+
+	if (range->type == req->type) {
+		switch (req->type) {
+		case ACRN_IOREQ_TYPE_MMIO:
+			if (req->reqs.mmio_request.address >= range->start &&
+			    (req->reqs.mmio_request.address +
+			     req->reqs.mmio_request.size - 1) <= range->end)
+				ret = true;
+			break;
+		case ACRN_IOREQ_TYPE_PORTIO:
+			if (req->reqs.pio_request.address >= range->start &&
+			    (req->reqs.pio_request.address +
+			     req->reqs.pio_request.size - 1) <= range->end)
+				ret = true;
+			break;
+		default:
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static struct acrn_ioreq_client *find_ioreq_client(struct acrn_vm *vm,
+						   struct acrn_io_request *req)
+{
+	struct acrn_ioreq_client *client, *found = NULL;
+	struct acrn_ioreq_range *range;
+
+	lockdep_assert_held(&vm->ioreq_clients_lock);
+
+	list_for_each_entry(client, &vm->ioreq_clients, list) {
+		read_lock_bh(&client->range_lock);
+		list_for_each_entry(range, &client->range_list, list) {
+			if (in_range(range, req)) {
+				found = client;
+				break;
+			}
+		}
+		read_unlock_bh(&client->range_lock);
+		if (found)
+			break;
+	}
+	return found ? found : vm->default_client;
+}
+
+/**
+ * acrn_ioreq_client_create() - Create an ioreq client
+ * @vm:		The VM that this client belongs to
+ * @handler:	The ioreq_handler of ioreq client acrn_hsm will create a kernel
+ *		thread and call the handler to handle I/O requests.
+ * @priv:	Private data for the handler
+ * @is_default:	If it is the default client
+ * @name:	The name of ioreq client
+ *
+ * Return: acrn_ioreq_client pointer on success, NULL on error
+ */
+struct acrn_ioreq_client *acrn_ioreq_client_create(struct acrn_vm *vm,
+						   ioreq_handler_t handler,
+						   void *priv, bool is_default,
+						   const char *name)
+{
+	struct acrn_ioreq_client *client;
+
+	if (!handler && !is_default) {
+		dev_dbg(acrn_dev.this_device,
+			"Cannot create non-default client w/o handler!\n");
+		return NULL;
+	}
+	client = kzalloc(sizeof(*client), GFP_KERNEL);
+	if (!client)
+		return NULL;
+
+	client->handler = handler;
+	client->vm = vm;
+	client->priv = priv;
+	client->is_default = is_default;
+	if (name)
+		strncpy(client->name, name, sizeof(client->name) - 1);
+	rwlock_init(&client->range_lock);
+	INIT_LIST_HEAD(&client->range_list);
+	init_waitqueue_head(&client->wq);
+
+	if (client->handler) {
+		client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
+					     client->vm->vmid, client->name);
+		if (IS_ERR(client->thread)) {
+			kfree(client);
+			return NULL;
+		}
+	}
+
+	spin_lock_bh(&vm->ioreq_clients_lock);
+	if (is_default)
+		vm->default_client = client;
+	else
+		list_add(&client->list, &vm->ioreq_clients);
+	spin_unlock_bh(&vm->ioreq_clients_lock);
+
+	dev_dbg(acrn_dev.this_device, "Created ioreq client %s.\n", name);
+	return client;
+}
+
+/**
+ * acrn_ioreq_client_destroy() - Destroy an ioreq client
+ * @client:	The ioreq client
+ */
+void acrn_ioreq_client_destroy(struct acrn_ioreq_client *client)
+{
+	struct acrn_ioreq_range *range, *next;
+	struct acrn_vm *vm = client->vm;
+
+	dev_dbg(acrn_dev.this_device,
+		"Destroy ioreq client %s.\n", client->name);
+	ioreq_pause();
+	set_bit(ACRN_IOREQ_CLIENT_DESTROYING, &client->flags);
+	if (client->is_default)
+		wake_up_interruptible(&client->wq);
+	else
+		kthread_stop(client->thread);
+
+	spin_lock_bh(&vm->ioreq_clients_lock);
+	if (client->is_default)
+		vm->default_client = NULL;
+	else
+		list_del(&client->list);
+	spin_unlock_bh(&vm->ioreq_clients_lock);
+
+	write_lock_bh(&client->range_lock);
+	list_for_each_entry_safe(range, next, &client->range_list, list) {
+		list_del(&range->list);
+		kfree(range);
+	}
+	write_unlock_bh(&client->range_lock);
+	kfree(client);
+
+	ioreq_resume();
+}
+
+static int acrn_ioreq_dispatch(struct acrn_vm *vm)
+{
+	struct acrn_ioreq_client *client;
+	struct acrn_io_request *req;
+	int i;
+
+	for (i = 0; i < vm->vcpu_num; i++) {
+		req = vm->ioreq_buf->req_slot + i;
+
+		/* barrier the read of processed of acrn_io_request */
+		if (smp_load_acquire(&req->processed) ==
+				     ACRN_IOREQ_STATE_PENDING) {
+			/* Complete the IO request directly in clearing stage */
+			if (test_bit(ACRN_VM_FLAG_CLEARING_IOREQ, &vm->flags)) {
+				ioreq_complete_request(vm, i, req);
+				continue;
+			}
+
+			spin_lock_bh(&vm->ioreq_clients_lock);
+			client = find_ioreq_client(vm, req);
+			if (!client) {
+				dev_err(acrn_dev.this_device,
+					"Failed to find ioreq client!\n");
+				spin_unlock_bh(&vm->ioreq_clients_lock);
+				return -EINVAL;
+			}
+			if (!client->is_default)
+				req->kernel_handled = 1;
+			else
+				req->kernel_handled = 0;
+			/*
+			 * Add barrier() to make sure the writes are done
+			 * before setting ACRN_IOREQ_STATE_PROCESSING
+			 */
+			smp_store_release(&req->processed,
+					  ACRN_IOREQ_STATE_PROCESSING);
+			set_bit(i, client->ioreqs_map);
+			wake_up_interruptible(&client->wq);
+			spin_unlock_bh(&vm->ioreq_clients_lock);
+		}
+	}
+
+	return 0;
+}
+
+static void ioreq_dispatcher(struct work_struct *work)
+{
+	struct acrn_vm *vm;
+
+	read_lock(&acrn_vm_list_lock);
+	list_for_each_entry(vm, &acrn_vm_list, list) {
+		if (!vm->ioreq_buf)
+			break;
+		acrn_ioreq_dispatch(vm);
+	}
+	read_unlock(&acrn_vm_list_lock);
+}
+
+static void ioreq_intr_handler(void)
+{
+	queue_work(ioreq_wq, &ioreq_work);
+}
+
+static void ioreq_pause(void)
+{
+	/* Flush and unarm the handler to ensure no I/O requests pending */
+	acrn_remove_intr_handler();
+	drain_workqueue(ioreq_wq);
+}
+
+static void ioreq_resume(void)
+{
+	/* Schedule after enabling in case other clients miss interrupt */
+	acrn_setup_intr_handler(ioreq_intr_handler);
+	queue_work(ioreq_wq, &ioreq_work);
+}
+
+int acrn_ioreq_intr_setup(void)
+{
+	acrn_setup_intr_handler(ioreq_intr_handler);
+	ioreq_wq = alloc_workqueue("ioreq_wq",
+				   WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_UNBOUND, 1);
+	if (!ioreq_wq) {
+		dev_err(acrn_dev.this_device, "Failed to alloc workqueue!\n");
+		acrn_remove_intr_handler();
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+void acrn_ioreq_intr_remove(void)
+{
+	if (ioreq_wq)
+		destroy_workqueue(ioreq_wq);
+	acrn_remove_intr_handler();
+}
+
+int acrn_ioreq_init(struct acrn_vm *vm, u64 buf_vma)
+{
+	struct acrn_ioreq_buffer *set_buffer;
+	struct page *page;
+	int ret;
+
+	if (vm->ioreq_buf)
+		return -EEXIST;
+
+	set_buffer = kzalloc(sizeof(*set_buffer), GFP_KERNEL);
+	if (!set_buffer)
+		return -ENOMEM;
+
+	ret = pin_user_pages_fast(buf_vma, 1,
+				  FOLL_WRITE | FOLL_LONGTERM, &page);
+	if (unlikely(ret != 1) || !page) {
+		dev_err(acrn_dev.this_device, "Failed to pin ioreq page!\n");
+		ret = -EFAULT;
+		goto free_buf;
+	}
+
+	vm->ioreq_buf = page_address(page);
+	vm->ioreq_page = page;
+	set_buffer->ioreq_buf = page_to_phys(page);
+	ret = hcall_set_ioreq_buffer(vm->vmid, virt_to_phys(set_buffer));
+	if (ret < 0) {
+		dev_err(acrn_dev.this_device, "Failed to init ioreq buffer!\n");
+		unpin_user_page(page);
+		vm->ioreq_buf = NULL;
+		goto free_buf;
+	}
+
+	dev_dbg(acrn_dev.this_device,
+		"Init ioreq buffer %pK!\n", vm->ioreq_buf);
+	ret = 0;
+free_buf:
+	kfree(set_buffer);
+	return ret;
+}
+
+void acrn_ioreq_deinit(struct acrn_vm *vm)
+{
+	struct acrn_ioreq_client *client, *next;
+
+	dev_dbg(acrn_dev.this_device,
+		"Deinit ioreq buffer %pK!\n", vm->ioreq_buf);
+	/* Destroy all clients belonging to this VM */
+	list_for_each_entry_safe(client, next, &vm->ioreq_clients, list)
+		acrn_ioreq_client_destroy(client);
+	if (vm->default_client)
+		acrn_ioreq_client_destroy(vm->default_client);
+
+	if (vm->ioreq_buf && vm->ioreq_page) {
+		unpin_user_page(vm->ioreq_page);
+		vm->ioreq_buf = NULL;
+	}
+}