[PATCH v13 19/24] virt: gunyah: Add IO handlers

[Elliot Berman <quic_eberman@quicinc.com>]

Add framework for VM functions to handle stage-2 write faults from Gunyah
guest virtual machines. IO handlers have a range of addresses which they
apply to. Optionally, they may apply to only when the value written
matches the IO handler's value.

Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
 drivers/virt/gunyah/vm_mgr.c  | 104 ++++++++++++++++++++++++++++++++++
 drivers/virt/gunyah/vm_mgr.h  |   4 ++
 include/linux/gunyah_vm_mgr.h |  25 ++++++++
 3 files changed, 133 insertions(+)

diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
index 6228090aceb6..81b42ab675f6 100644
--- a/drivers/virt/gunyah/vm_mgr.c
+++ b/drivers/virt/gunyah/vm_mgr.c
@@ -279,6 +279,108 @@ static void gh_vm_clean_resources(struct gh_vm *ghvm)
 	mutex_unlock(&ghvm->resources_lock);
 }
 
+static int _gh_vm_io_handler_compare(const struct rb_node *node, const struct rb_node *parent)
+{
+	struct gh_vm_io_handler *n = container_of(node, struct gh_vm_io_handler, node);
+	struct gh_vm_io_handler *p = container_of(parent, struct gh_vm_io_handler, node);
+
+	if (n->addr < p->addr)
+		return -1;
+	if (n->addr > p->addr)
+		return 1;
+	if ((n->len && !p->len) || (!n->len && p->len))
+		return 0;
+	if (n->len < p->len)
+		return -1;
+	if (n->len > p->len)
+		return 1;
+	/* one of the io handlers doesn't have datamatch and the other does.
+	 * For purposes of comparison, that makes them identical since the
+	 * one that doesn't have datamatch will cover the same handler that
+	 * does.
+	 */
+	if (n->datamatch != p->datamatch)
+		return 0;
+	if (n->data < p->data)
+		return -1;
+	if (n->data > p->data)
+		return 1;
+	return 0;
+}
+
+static int gh_vm_io_handler_compare(struct rb_node *node, const struct rb_node *parent)
+{
+	return _gh_vm_io_handler_compare(node, parent);
+}
+
+static int gh_vm_io_handler_find(const void *key, const struct rb_node *node)
+{
+	const struct gh_vm_io_handler *k = key;
+
+	return _gh_vm_io_handler_compare(&k->node, node);
+}
+
+static struct gh_vm_io_handler *gh_vm_mgr_find_io_hdlr(struct gh_vm *ghvm, u64 addr,
+								u64 len, u64 data)
+{
+	struct gh_vm_io_handler key = {
+		.addr = addr,
+		.len = len,
+		.datamatch = true,
+		.data = data,
+	};
+	struct rb_node *node;
+
+	node = rb_find(&key, &ghvm->mmio_handler_root, gh_vm_io_handler_find);
+	if (!node)
+		return NULL;
+
+	return container_of(node, struct gh_vm_io_handler, node);
+}
+
+int gh_vm_mmio_write(struct gh_vm *ghvm, u64 addr, u32 len, u64 data)
+{
+	struct gh_vm_io_handler *io_hdlr = NULL;
+	int ret;
+
+	down_read(&ghvm->mmio_handler_lock);
+	io_hdlr = gh_vm_mgr_find_io_hdlr(ghvm, addr, len, data);
+	if (!io_hdlr || !io_hdlr->ops || !io_hdlr->ops->write) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	ret = io_hdlr->ops->write(io_hdlr, addr, len, data);
+
+out:
+	up_read(&ghvm->mmio_handler_lock);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gh_vm_mmio_write);
+
+int gh_vm_add_io_handler(struct gh_vm *ghvm, struct gh_vm_io_handler *io_hdlr)
+{
+	struct rb_node *found;
+
+	if (io_hdlr->datamatch && (!io_hdlr->len || io_hdlr->len > sizeof(io_hdlr->data)))
+		return -EINVAL;
+
+	down_write(&ghvm->mmio_handler_lock);
+	found = rb_find_add(&io_hdlr->node, &ghvm->mmio_handler_root, gh_vm_io_handler_compare);
+	up_write(&ghvm->mmio_handler_lock);
+
+	return found ? -EEXIST : 0;
+}
+EXPORT_SYMBOL_GPL(gh_vm_add_io_handler);
+
+void gh_vm_remove_io_handler(struct gh_vm *ghvm, struct gh_vm_io_handler *io_hdlr)
+{
+	down_write(&ghvm->mmio_handler_lock);
+	rb_erase(&io_hdlr->node, &ghvm->mmio_handler_root);
+	up_write(&ghvm->mmio_handler_lock);
+}
+EXPORT_SYMBOL_GPL(gh_vm_remove_io_handler);
+
 static int gh_vm_rm_notification_status(struct gh_vm *ghvm, void *data)
 {
 	struct gh_rm_vm_status_payload *payload = data;
@@ -364,6 +466,8 @@ static __must_check struct gh_vm *gh_vm_alloc(struct gh_rm *rm)
 	mutex_init(&ghvm->resources_lock);
 	INIT_LIST_HEAD(&ghvm->resources);
 	INIT_LIST_HEAD(&ghvm->resource_tickets);
+	init_rwsem(&ghvm->mmio_handler_lock);
+	ghvm->mmio_handler_root = RB_ROOT;
 	INIT_LIST_HEAD(&ghvm->functions);
 	ghvm->vm_status = GH_RM_VM_STATUS_NO_STATE;
 
diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
index e5e0c92d4cb1..3fc0f91dfd1a 100644
--- a/drivers/virt/gunyah/vm_mgr.h
+++ b/drivers/virt/gunyah/vm_mgr.h
@@ -56,10 +56,14 @@ struct gh_vm {
 	struct mutex resources_lock;
 	struct list_head resources;
 	struct list_head resource_tickets;
+	struct rb_root mmio_handler_root;
+	struct rw_semaphore mmio_handler_lock;
 };
 
 int gh_vm_mem_alloc(struct gh_vm *ghvm, struct gh_userspace_memory_region *region);
 void gh_vm_mem_reclaim(struct gh_vm *ghvm);
 struct gh_vm_mem *gh_vm_mem_find_by_addr(struct gh_vm *ghvm, u64 guest_phys_addr, u32 size);
 
+int gh_vm_mmio_write(struct gh_vm *ghvm, u64 addr, u32 len, u64 data);
+
 #endif
diff --git a/include/linux/gunyah_vm_mgr.h b/include/linux/gunyah_vm_mgr.h
index e3a6666d7529..0fa3cf6bcaca 100644
--- a/include/linux/gunyah_vm_mgr.h
+++ b/include/linux/gunyah_vm_mgr.h
@@ -98,4 +98,29 @@ struct gh_vm_resource_ticket {
 int gh_vm_add_resource_ticket(struct gh_vm *ghvm, struct gh_vm_resource_ticket *ticket);
 void gh_vm_remove_resource_ticket(struct gh_vm *ghvm, struct gh_vm_resource_ticket *ticket);
 
+/*
+ * gh_vm_io_handler contains the info about an io device and its associated
+ * addr and the ops associated with the io device.
+ */
+struct gh_vm_io_handler {
+	struct rb_node node;
+	u64 addr;
+
+	bool datamatch;
+	u8 len;
+	u64 data;
+	struct gh_vm_io_handler_ops *ops;
+};
+
+/*
+ * gh_vm_io_handler_ops contains function pointers associated with an iodevice.
+ */
+struct gh_vm_io_handler_ops {
+	int (*read)(struct gh_vm_io_handler *io_dev, u64 addr, u32 len, u64 data);
+	int (*write)(struct gh_vm_io_handler *io_dev, u64 addr, u32 len, u64 data);
+};
+
+int gh_vm_add_io_handler(struct gh_vm *ghvm, struct gh_vm_io_handler *io_dev);
+void gh_vm_remove_io_handler(struct gh_vm *ghvm, struct gh_vm_io_handler *io_dev);
+
 #endif
-- 
2.40.0