1 files changed, 244 insertions, 0 deletions
diff --git a/drivers/virt/acrn/irqfd.c b/drivers/virt/acrn/irqfd.c
new file mode 100644
index 000000000..ac583c843
--- /dev/null
+++ b/drivers/virt/acrn/irqfd.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACRN HSM irqfd: use eventfd objects to inject virtual interrupts
+ *
+ * Copyright (C) 2020 Intel Corporation. All rights reserved.
+ *
+ * Authors:
+ *	Shuo Liu <shuo.a.liu@intel.com>
+ *	Yakui Zhao <yakui.zhao@intel.com>
+ */
+
+#include <linux/eventfd.h>
+#include <linux/file.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+
+#include "acrn_drv.h"
+
+/* Cleanup work has been queued; set via test_and_set_bit(). */
+#define HSM_IRQFD_FLAG_SHUTDOWN	0
+
+/**
+ * struct hsm_irqfd - Properties of HSM irqfd
+ * @vm:		Associated VM pointer
+ * @wait:	Entry of wait-queue
+ * @shutdown:	Async shutdown work
+ * @eventfd:	Associated eventfd
+ * @list:	Entry within &acrn_vm.irqfds of irqfds of a VM
+ * @pt:		Structure for select/poll on the associated eventfd
+ * @msi:	MSI data
+ * @flags:	Internal lifecycle flags (HSM_IRQFD_FLAG_*)
+ */
+struct hsm_irqfd {
+	struct acrn_vm		*vm;
+	wait_queue_entry_t	wait;
+	struct work_struct	shutdown;
+	struct eventfd_ctx	*eventfd;
+	struct list_head	list;
+	poll_table		pt;
+	struct acrn_msi_entry	msi;
+	unsigned long		flags;
+};
+
+static void acrn_irqfd_inject(struct hsm_irqfd *irqfd)
+{
+	struct acrn_vm *vm = irqfd->vm;
+
+	acrn_msi_inject(vm, irqfd->msi.msi_addr,
+			irqfd->msi.msi_data);
+}
+
+/* Queue the cleanup work at most once. Safe from atomic context. */
+static void hsm_irqfd_queue_shutdown(struct hsm_irqfd *irqfd)
+{
+	if (!test_and_set_bit(HSM_IRQFD_FLAG_SHUTDOWN, &irqfd->flags))
+		queue_work(irqfd->vm->irqfd_wq, &irqfd->shutdown);
+}
+
+/* Sole owner of @irqfd: unhook waitqueue, drop eventfd ref, free. */
+static void hsm_irqfd_shutdown_work(struct work_struct *work)
+{
+	struct hsm_irqfd *irqfd = container_of(work, struct hsm_irqfd,
+					       shutdown);
+	struct acrn_vm *vm = irqfd->vm;
+	u64 cnt;
+
+	mutex_lock(&vm->irqfds_lock);
+	if (!list_empty(&irqfd->list))
+		list_del_init(&irqfd->list);
+	mutex_unlock(&vm->irqfds_lock);
+
+	eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
+	eventfd_ctx_put(irqfd->eventfd);
+	kfree(irqfd);
+}
+
+/* Called with wqh->lock held and interrupts disabled */
+static int hsm_irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode,
+			    int sync, void *key)
+{
+	unsigned long poll_bits = (unsigned long)key;
+	struct hsm_irqfd *irqfd;
+
+	irqfd = container_of(wait, struct hsm_irqfd, wait);
+
+	if (poll_bits & POLLIN)
+		/* An event has been signaled, inject an interrupt */
+		acrn_irqfd_inject(irqfd);
+
+	if (poll_bits & POLLHUP)
+		/* Defer teardown to the cleanup work; can't sleep here. */
+		hsm_irqfd_queue_shutdown(irqfd);
+
+	return 0;
+}
+
+static void hsm_irqfd_poll_func(struct file *file, wait_queue_head_t *wqh,
+				poll_table *pt)
+{
+	struct hsm_irqfd *irqfd;
+
+	irqfd = container_of(pt, struct hsm_irqfd, pt);
+	add_wait_queue(wqh, &irqfd->wait);
+}
+
+/*
+ * Assign an eventfd to a VM and create a HSM irqfd associated with the
+ * eventfd. The properties of the HSM irqfd are built from a &struct
+ * acrn_irqfd.
+ */
+static int acrn_irqfd_assign(struct acrn_vm *vm, struct acrn_irqfd *args)
+{
+	struct eventfd_ctx *eventfd = NULL;
+	struct hsm_irqfd *irqfd, *tmp;
+	__poll_t events;
+	int ret = 0;
+
+	irqfd = kzalloc_obj(*irqfd);
+	if (!irqfd)
+		return -ENOMEM;
+
+	irqfd->vm = vm;
+	memcpy(&irqfd->msi, &args->msi, sizeof(args->msi));
+	INIT_LIST_HEAD(&irqfd->list);
+	INIT_WORK(&irqfd->shutdown, hsm_irqfd_shutdown_work);
+
+	CLASS(fd, f)(args->fd);
+	if (fd_empty(f)) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	eventfd = eventfd_ctx_fileget(fd_file(f));
+	if (IS_ERR(eventfd)) {
+		ret = PTR_ERR(eventfd);
+		goto out;
+	}
+
+	irqfd->eventfd = eventfd;
+
+	/*
+	 * Install custom wake-up handling to be notified whenever underlying
+	 * eventfd is signaled.
+	 */
+	init_waitqueue_func_entry(&irqfd->wait, hsm_irqfd_wakeup);
+	init_poll_funcptr(&irqfd->pt, hsm_irqfd_poll_func);
+
+	/*
+	 * Hold irqfds_lock across waitqueue install and list_add so the
+	 * irqfd is not visible to deassign/deinit before its waitqueue
+	 * entry is in place, and any racing EPOLLHUP cleanup work blocks
+	 * on irqfds_lock until publication completes.
+	 */
+	mutex_lock(&vm->irqfds_lock);
+	list_for_each_entry(tmp, &vm->irqfds, list) {
+		if (irqfd->eventfd != tmp->eventfd)
+			continue;
+		ret = -EBUSY;
+		mutex_unlock(&vm->irqfds_lock);
+		goto fail;
+	}
+
+	events = vfs_poll(fd_file(f), &irqfd->pt);
+	list_add_tail(&irqfd->list, &vm->irqfds);
+	if (events & EPOLLIN)
+		acrn_irqfd_inject(irqfd);
+	mutex_unlock(&vm->irqfds_lock);
+
+	return 0;
+fail:
+	eventfd_ctx_put(eventfd);
+out:
+	kfree(irqfd);
+	return ret;
+}
+
+static int acrn_irqfd_deassign(struct acrn_vm *vm,
+			       struct acrn_irqfd *args)
+{
+	struct hsm_irqfd *irqfd, *tmp;
+	struct eventfd_ctx *eventfd;
+
+	eventfd = eventfd_ctx_fdget(args->fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	mutex_lock(&vm->irqfds_lock);
+	list_for_each_entry_safe(irqfd, tmp, &vm->irqfds, list) {
+		if (irqfd->eventfd == eventfd) {
+			list_del_init(&irqfd->list);
+			hsm_irqfd_queue_shutdown(irqfd);
+			break;
+		}
+	}
+	mutex_unlock(&vm->irqfds_lock);
+	eventfd_ctx_put(eventfd);
+
+	/* Wait for cleanup work to finish so the eventfd is fully detached. */
+	flush_workqueue(vm->irqfd_wq);
+
+	return 0;
+}
+
+int acrn_irqfd_config(struct acrn_vm *vm, struct acrn_irqfd *args)
+{
+	int ret;
+
+	if (args->flags & ACRN_IRQFD_FLAG_DEASSIGN)
+		ret = acrn_irqfd_deassign(vm, args);
+	else
+		ret = acrn_irqfd_assign(vm, args);
+
+	return ret;
+}
+
+int acrn_irqfd_init(struct acrn_vm *vm)
+{
+	INIT_LIST_HEAD(&vm->irqfds);
+	mutex_init(&vm->irqfds_lock);
+	vm->irqfd_wq = alloc_workqueue("acrn_irqfd-%u", WQ_PERCPU, 0, vm->vmid);
+	if (!vm->irqfd_wq)
+		return -ENOMEM;
+
+	dev_dbg(acrn_dev.this_device, "VM %u irqfd init.\n", vm->vmid);
+	return 0;
+}
+
+void acrn_irqfd_deinit(struct acrn_vm *vm)
+{
+	struct hsm_irqfd *irqfd, *next;
+
+	dev_dbg(acrn_dev.this_device, "VM %u irqfd deinit.\n", vm->vmid);
+
+	mutex_lock(&vm->irqfds_lock);
+	list_for_each_entry_safe(irqfd, next, &vm->irqfds, list) {
+		list_del_init(&irqfd->list);
+		hsm_irqfd_queue_shutdown(irqfd);
+	}
+	mutex_unlock(&vm->irqfds_lock);
+
+	/* Drain all cleanup work before tearing the workqueue down. */
+	flush_workqueue(vm->irqfd_wq);
+	destroy_workqueue(vm->irqfd_wq);
+}