virt: acrn: Introduce interfaces for PCI device passthrough

virt: acrn: Introduce interfaces for PCI device passthrough

PCI device passthrough enables an OS in a virtual machine to directly
access a PCI device in the host. It promises almost the native
performance, which is required in performance-critical scenarios of
ACRN.

HSM provides the following ioctls:
 - Assign - ACRN_IOCTL_ASSIGN_PCIDEV
   Pass data struct acrn_pcidev from userspace to the hypervisor, and
   inform the hypervisor to assign a PCI device to a User VM.

 - De-assign - ACRN_IOCTL_DEASSIGN_PCIDEV
   Pass data struct acrn_pcidev from userspace to the hypervisor, and
   inform the hypervisor to de-assign a PCI device from a User VM.

 - Set a interrupt of a passthrough device - ACRN_IOCTL_SET_PTDEV_INTR
   Pass data struct acrn_ptdev_irq from userspace to the hypervisor,
   and inform the hypervisor to map a INTx interrupt of passthrough
   device of User VM.

 - Reset passthrough device interrupt - ACRN_IOCTL_RESET_PTDEV_INTR
   Pass data struct acrn_ptdev_irq from userspace to the hypervisor,
   and inform the hypervisor to unmap a INTx interrupt of passthrough
   device of User VM.

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>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20210207031040.49576-12-shuo.a.liu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>