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, 150 insertions, 0 deletions

diff --git a/include/uapi/linux/acrn.h b/include/uapi/linux/acrn.h
index ec4c61e7c170..b0f73ab5e4e8 100644
--- a/include/uapi/linux/acrn.h
+++ b/include/uapi/linux/acrn.h
@@ -14,6 +14,145 @@
 #include <linux/types.h>
 #include <linux/uuid.h>
 
+#define ACRN_IO_REQUEST_MAX		16
+
+#define ACRN_IOREQ_STATE_PENDING	0
+#define ACRN_IOREQ_STATE_COMPLETE	1
+#define ACRN_IOREQ_STATE_PROCESSING	2
+#define ACRN_IOREQ_STATE_FREE		3
+
+#define ACRN_IOREQ_TYPE_PORTIO		0
+#define ACRN_IOREQ_TYPE_MMIO		1
+
+#define ACRN_IOREQ_DIR_READ		0
+#define ACRN_IOREQ_DIR_WRITE		1
+
+/**
+ * struct acrn_mmio_request - Info of a MMIO I/O request
+ * @direction:	Access direction of this request (ACRN_IOREQ_DIR_*)
+ * @reserved:	Reserved for alignment and should be 0
+ * @address:	Access address of this MMIO I/O request
+ * @size:	Access size of this MMIO I/O request
+ * @value:	Read/write value of this MMIO I/O request
+ */
+struct acrn_mmio_request {
+	__u32	direction;
+	__u32	reserved;
+	__u64	address;
+	__u64	size;
+	__u64	value;
+};
+
+/**
+ * struct acrn_pio_request - Info of a PIO I/O request
+ * @direction:	Access direction of this request (ACRN_IOREQ_DIR_*)
+ * @reserved:	Reserved for alignment and should be 0
+ * @address:	Access address of this PIO I/O request
+ * @size:	Access size of this PIO I/O request
+ * @value:	Read/write value of this PIO I/O request
+ */
+struct acrn_pio_request {
+	__u32	direction;
+	__u32	reserved;
+	__u64	address;
+	__u64	size;
+	__u32	value;
+};
+
+/**
+ * struct acrn_io_request - 256-byte ACRN I/O request
+ * @type:		Type of this request (ACRN_IOREQ_TYPE_*).
+ * @completion_polling:	Polling flag. Hypervisor will poll completion of the
+ *			I/O request if this flag set.
+ * @reserved0:		Reserved fields.
+ * @reqs:		Union of different types of request. Byte offset: 64.
+ * @reqs.pio_request:	PIO request data of the I/O request.
+ * @reqs.mmio_request:	MMIO request data of the I/O request.
+ * @reqs.data:		Raw data of the I/O request.
+ * @reserved1:		Reserved fields.
+ * @kernel_handled:	Flag indicates this request need be handled in kernel.
+ * @processed:		The status of this request (ACRN_IOREQ_STATE_*).
+ *
+ * The state transitions of ACRN I/O request:
+ *
+ *    FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...
+ *
+ * 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.
+ *
+ * On basis of the states illustrated above, a typical lifecycle of ACRN IO
+ * request would look like:
+ *
+ * Flow                 (assume the initial state is FREE)
+ * |
+ * |   Service VM vCPU 0     Service VM vCPU x      User vCPU y
+ * |
+ * |                                             hypervisor:
+ * |                                               fills in type, addr, etc.
+ * |                                               pauses the User VM vCPU y
+ * |                                               sets the state to PENDING (a)
+ * |                                               fires an upcall to Service VM
+ * |
+ * | HSM:
+ * |  scans for PENDING requests
+ * |  sets the states to PROCESSING (b)
+ * |  assigns the requests to clients (c)
+ * V
+ * |                     client:
+ * |                       scans for the assigned requests
+ * |                       handles the requests (d)
+ * |                     HSM:
+ * |                       sets states to COMPLETE
+ * |                       notifies the hypervisor
+ * |
+ * |                     hypervisor:
+ * |                       resumes User VM vCPU y (e)
+ * |
+ * |                                             hypervisor:
+ * |                                               post handling (f)
+ * V                                               sets states to FREE
+ *
+ * Note that the procedures (a) to (f) in the illustration above require to be
+ * strictly processed in the order.  One vCPU cannot trigger another request of
+ * I/O emulation before completing the previous one.
+ *
+ * Atomic and barriers are required when HSM and hypervisor accessing the state
+ * of &struct acrn_io_request.
+ *
+ */
+struct acrn_io_request {
+	__u32	type;
+	__u32	completion_polling;
+	__u32	reserved0[14];
+	union {
+		struct acrn_pio_request		pio_request;
+		struct acrn_mmio_request	mmio_request;
+		__u64				data[8];
+	} reqs;
+	__u32	reserved1;
+	__u32	kernel_handled;
+	__u32	processed;
+} __attribute__((aligned(256)));
+
+struct acrn_io_request_buffer {
+	union {
+		struct acrn_io_request	req_slot[ACRN_IO_REQUEST_MAX];
+		__u8			reserved[4096];
+	};
+};
+
+/**
+ * struct acrn_ioreq_notify - The structure of ioreq completion notification
+ * @vmid:	User VM ID
+ * @reserved:	Reserved and should be 0
+ * @vcpu:	vCPU ID
+ */
+struct acrn_ioreq_notify {
+	__u16	vmid;
+	__u16	reserved;
+	__u32	vcpu;
+};
+
 /**
  * struct acrn_vm_creation - Info to create a User VM
  * @vmid:		User VM ID returned from the hypervisor
@@ -218,6 +357,17 @@ struct acrn_vm_memmap {
 #define ACRN_IOCTL_SET_VCPU_REGS	\
 	_IOW(ACRN_IOCTL_TYPE, 0x16, struct acrn_vcpu_regs)
 
+#define ACRN_IOCTL_NOTIFY_REQUEST_FINISH \
+	_IOW(ACRN_IOCTL_TYPE, 0x31, struct acrn_ioreq_notify)
+#define ACRN_IOCTL_CREATE_IOREQ_CLIENT	\
+	_IO(ACRN_IOCTL_TYPE, 0x32)
+#define ACRN_IOCTL_ATTACH_IOREQ_CLIENT	\
+	_IO(ACRN_IOCTL_TYPE, 0x33)
+#define ACRN_IOCTL_DESTROY_IOREQ_CLIENT	\
+	_IO(ACRN_IOCTL_TYPE, 0x34)
+#define ACRN_IOCTL_CLEAR_VM_IOREQ	\
+	_IO(ACRN_IOCTL_TYPE, 0x35)
+
 #define ACRN_IOCTL_SET_MEMSEG		\
 	_IOW(ACRN_IOCTL_TYPE, 0x41, struct acrn_vm_memmap)
 #define ACRN_IOCTL_UNSET_MEMSEG		\