Hi All,
Over the past week, I have been working to come up with a solution to
the
memory transfer performance issues that hinder the Looking Glass
Project.
Currently Looking Glass works by using the IVSHMEM shared memory device
which
is fed by an application that captures the guest's video output. While
this
works it is sub-optimal because we first have to perform a CPU copy of
the
captured frame into shared RAM, and then back out again for display.
Because
the destination buffers are allocated by closed proprietary code
(DirectX, or
NVidia NvFBC) there is no way to have the frame placed directly into the
IVSHMEM shared ram.
This new device, currently named `introspection` (which needs a more
suitable
name, porthole perhaps?), provides a means of translating guest physical
addresses to host virtual addresses, and finally to the host offsets in
RAM for
file-backed memory guests. It does this by means of a simple protocol
over a
unix socket (chardev) which is supplied the appropriate fd for the VM's
system
RAM. The guest (in this case, Windows), when presented with the address
of a
userspace buffer and size, will mlock the appropriate pages into RAM and
pass
guest physical addresses to the virtual device.
This device and the windows driver have been designed in such a way that
it's a
utility device for any project and/or application that could make use of
it.
The PCI subsystem vendor and device ID are used to provide a means of
device
identification in cases where multiple devices may be in use for
differing
applications. This also allows one common driver to be used for any
other
projects wishing to build on this device.
My ultimate goal is to get this to a state where it could be accepted
upstream
into Qemu at which point Looking Glass would be modified to use it
instead of
the IVSHMEM device.
My git repository with the new device can be found at:
https://github.com/gnif/qemu
The new device is:
https://github.com/gnif/qemu/blob/master/hw/misc/introspection.c
Looking Glass:
https://looking-glass.hostfission.com/
The windows driver, while working, needs some cleanup before the source
is
published. I intend to maintain both this device and the windows driver
including producing a signed Windows 10 driver if Redhat are unwilling
or
unable.
Kind Regards,
Geoffrey McRae
HostFission
https://hostfission.com
