virtio-devices: Add Vdpa device

vDPA is a kernel framework introduced fairly recently in order to handle
devices complying with virtio specification on their datapath, while the
control path is vendor specific. For the datapath, that means the
virtqueues are handled through DMA directly between the hardware and the
guest, while the control path goes through the vDPA framework,
eventually exposed through a vhost-vdpa device.

vDPA, like VFIO, aims at achieving baremetal performance for devices
that are passed into a VM. But unlike VFIO, it provides a simpler/better
framework for achieving migration. Because the DMA accesses between the
device and the guest are going through virtio queues, migration can be
achieved way more easily, and doesn't require each device driver to
implement the migration support. In the VFIO case, each vendor is
expected to provide an implementation of the VFIO migration framework,
which makes things harder as it must be done for each and every device.

So to summarize the point is to support migration for hardware devices
through which we can achieve baremetal performances.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/lib.rs

@@ -34,6 +34,7 @@ mod rng;
 pub mod seccomp_filters;
 mod thread_helper;
 pub mod transport;
+pub mod vdpa;
 pub mod vhost_user;
 pub mod vsock;
 pub mod watchdog;
@@ -48,6 +49,7 @@ pub use self::mem::*;
 pub use self::net::*;
 pub use self::pmem::*;
 pub use self::rng::*;
+pub use self::vdpa::*;
 pub use self::vsock::*;
 pub use self::watchdog::*;
 use vm_memory::{bitmap::AtomicBitmap, GuestAddress, GuestMemory};
@@ -100,6 +102,8 @@ pub enum ActivateError {
     CreateSeccompFilter(seccompiler::Error),
     /// Cannot create rate limiter
     CreateRateLimiter(std::io::Error),
+    /// Failed activating the vDPA device
+    ActivateVdpa(vdpa::Error),
 }
 
 pub type ActivateResult = std::result::Result<(), ActivateError>;
@@ -110,6 +114,7 @@ pub type DeviceEventT = u16;
 pub enum Error {
     FailedSignalingUsedQueue(io::Error),
     IoError(io::Error),
+    VdpaUpdateMemory(vdpa::Error),
     VhostUserUpdateMemory(vhost_user::Error),
     VhostUserAddMemoryRegion(vhost_user::Error),
     SetShmRegionsNotSupported,