Re: [Qemu-devel] About making QEMU to LIBs!

[Stefan Hajnoczi]

On Tue, Mar 26, 2019 at 03:00:05PM +0800, Xiao Guangrong wrote:
> On 3/26/19 7:18 AM, Paolo Bonzini wrote:
> > On 25/03/19 12:46, Yang Zhong wrote:
> > > Hello all,
> > > 
> > > Rust-VMM has started to make all features and common modules to crates, 
> > > and CSP can
> > > deploy their VMM on demand. This afternoon, Xiao guangrong and i talked 
> > > about the light
> > > weight VM solitions，and we thought QEMU can do same thing like Rust-vmm, 
> > > although we can
> > > make all modules or features in QEMU configurable, but making features 
> > > and modules to libs
> > > are still valuable for QEMU. Any comments are welcome! thanks!
> > 
> > What features/modules were you thinking of?  Were you thinking of
> > turning them into dynamically loaded libraries, or spinning them out
> > into separate projects (such as libslirp)?
> 
> We are considering make QEMU's device emulations to dynamically libraries 
> that include
> virtio devices, IO controller and even vCPU emulations plus some hooks into 
> it, and so
> on.
> 
> > 
> > Also, what is the use case?  Is it to reduce the attack surface without
> > having multiple QEMU binaries?
> > 
> 
> Security is one story we concern， only the essential and audited 
> modules/libraries
> can be loaded into memory.

QEMU's build system supports dynamically loaded "modules" (shared
libraries).  You can build all features but only load a subset of them
at runtime.  You can also install just a subset of modules on a host.

Examples are the block drivers and audio drivers.  See ./configure and
block/Makefile.objs.  QEMU's build system has 'y', 'n', and 'm' (for module).

So far no emulated devices are built as modules, but this would be a
good area to explore.

Do you think modules satisfy your requirements?

> Another story is that lightweight virt. becomes more and more important to 
> run VM-based
> workload in the public Cloud. However, QEMU is too huge and cumbersome to 
> fill our
> requirements, e.g, QEMU-lites has been being developed for a long time but 
> still lacks
> a way into mainline or Intel's nEMU more radically.

It's worth noting that NEMU functionality is being upstreamed or
inspired upstream work.  QEMU recently got Kconfig (better compile-time
dependency management) and PVH fast guest kernel loading.  If you are
interested in lightweight VMs, check out those features.

Stefan

signature.asc
Description: PGP signature