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, 20 insertions, 7 deletions

diff --git a/drivers/virt/acrn/vm.c b/drivers/virt/acrn/vm.c
index ff5df7acb551..2bc649c7c1d3 100644
--- a/drivers/virt/acrn/vm.c
+++ b/drivers/virt/acrn/vm.c
@@ -15,9 +15,12 @@
 #include "acrn_drv.h"
 
 /* List of VMs */
-static LIST_HEAD(acrn_vm_list);
-/* To protect acrn_vm_list */
-static DEFINE_MUTEX(acrn_vm_list_lock);
+LIST_HEAD(acrn_vm_list);
+/*
+ * acrn_vm_list is read in a worker thread which dispatch I/O requests and
+ * is wrote in VM creation ioctl. Use the rwlock mechanism to protect it.
+ */
+DEFINE_RWLOCK(acrn_vm_list_lock);
 
 struct acrn_vm *acrn_vm_create(struct acrn_vm *vm,
 			       struct acrn_vm_creation *vm_param)
@@ -32,12 +35,20 @@ struct acrn_vm *acrn_vm_create(struct acrn_vm *vm,
 	}
 
 	mutex_init(&vm->regions_mapping_lock);
+	INIT_LIST_HEAD(&vm->ioreq_clients);
+	spin_lock_init(&vm->ioreq_clients_lock);
 	vm->vmid = vm_param->vmid;
 	vm->vcpu_num = vm_param->vcpu_num;
 
-	mutex_lock(&acrn_vm_list_lock);
+	if (acrn_ioreq_init(vm, vm_param->ioreq_buf) < 0) {
+		hcall_destroy_vm(vm_param->vmid);
+		vm->vmid = ACRN_INVALID_VMID;
+		return NULL;
+	}
+
+	write_lock_bh(&acrn_vm_list_lock);
 	list_add(&vm->list, &acrn_vm_list);
-	mutex_unlock(&acrn_vm_list_lock);
+	write_unlock_bh(&acrn_vm_list_lock);
 
 	dev_dbg(acrn_dev.this_device, "VM %u created.\n", vm->vmid);
 	return vm;
@@ -52,9 +63,11 @@ int acrn_vm_destroy(struct acrn_vm *vm)
 		return 0;
 
 	/* Remove from global VM list */
-	mutex_lock(&acrn_vm_list_lock);
+	write_lock_bh(&acrn_vm_list_lock);
 	list_del_init(&vm->list);
-	mutex_unlock(&acrn_vm_list_lock);
+	write_unlock_bh(&acrn_vm_list_lock);
+
+	acrn_ioreq_deinit(vm);
 
 	ret = hcall_destroy_vm(vm->vmid);
 	if (ret < 0) {