Re: Inter-VM device emulation (call on Mon 20th July 2020)

[Stefan Hajnoczi]

Thank you everyone who joined!

I didn't take notes but two things stood out:

1. The ivshmem v2 and virtio-vhost-user use cases are quite different
so combining them does not seem realistic. ivshmem v2 needs to be as
simple for the hypervisor to implement as possible even if this
involves some sacrifices (e.g. not transparent to the Driver VM that
is accessing the device, performance). virtio-vhost-user is more aimed
at general-purpose device emulation although support for arbitrary
devices (e.g. PCI) would be important to serve all use cases.

2. Alexander Graf's idea for a new Linux driver that provides an
enforcing software IOMMU. This would be a character device driver that
is mmapped by the device emulation process (either vhost-user-style on
the host or another VMM for inter-VM device emulation). The Driver VMM
can program mappings into the device and the page tables in the device
emulation process will be updated. This way the Driver VMM can share
memory specific regions of guest RAM with the device emulation process
and revoke those mappings later.

Stefan