Hi Andra,

On Fri, Dec 04, 2020 at 07:02:31PM +0200, Andra Paraschiv wrote:

vsock enables communication between virtual machines and the host they are
running on. Nested VMs can be setup to use vsock channels, as the multi
transport support has been available in the mainline since the v5.5 Linux kernel
has been released.

Implicitly, if no host->guest vsock transport is loaded, all the vsock packets
are forwarded to the host. This behavior can be used to setup communication
channels between sibling VMs that are running on the same host. One example can
be the vsock channels that can be established within AWS Nitro Enclaves
(see Documentation/virt/ne_overview.rst).

To be able to explicitly mark a connection as being used for a certain use case,
add a flags field in the vsock address data structure. The "svm_reserved1" field
has been repurposed to be the flags field. The value of the flags will then be
taken into consideration when the vsock transport is assigned. This way can
distinguish between different use cases, such as nested VMs / local communication
and sibling VMs.

the series seems in a good shape, I left some minor comments.
I run my test suite (vsock_test, iperf3, nc) with nested VMs (QEMU/KVM), 
and everything looks good.

Note: I'll be offline today and tomorrow, so I may miss followups.

Thanks,
Stefano