[Qemu-devel] Para-virtualized ram-based filesystem?

["Ritchie, Stuart" <Stuart.Ritchie@tellabs.com>]

Hi all,

Has anyone looked at implementing a para-virtualized ram-based filesystem
for qemu?  Or any similar dynamic memory mapping techniques for running
guests?

What I had in mind would be a convenient, zero-copy mechanism for sharing
dynamically allocated, memory mapped files between host and guests.

The host provides a primary memory-mapped file system (ramfs, tmpfs,
hugetlbfs, etc), and the guest kernel and qemu use this host fs to provide
the illusion to guest applications that the filesystem is local.

The guest kernel contains a new filesystem, say call it vramfs,
implementing the various VFS handlers for a para-virt filesystem.  These
handlers call out to qemu, which in turn emulates them by invoking the
required host system calls.

Handling mmap/munmap is tricky -- but this is where the magic is.  There
does seem to be some qemu infrastructure to dynamically map memory into a
running system, though it may be designed for different requirements
(e.g., device memory).

I currently have the resources to work on this and am looking forward to
contributing my work back to the community.  I would appreciate any help
or pointers on this effort.

Cheers,
--Stuart


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