Re: [Qemu-devel] [RFC PATCH v2 09/35] multi-process: setup PCI host bridge for remote device

[Gerd Hoffmann <kraxel@redhat.com>]

On Mon, Jun 17, 2019 at 11:15:39AM -0700, elena.ufimtseva@oracle.com wrote:
> From: Jagannathan Raman <jag.raman@oracle.com>
> 
> PCI host bridge is setup for the remote device process. It is
> implemented using remote-pcihost object. It is an extension of the PCI
> host bridge setup by QEMU.
> Remote-pcihost configures a PCI bus which could be used by the remote
>  PCI device to latch on to.

Hmm, this (and at least the next two patches) look like you just fake
everything the device emulation needs in the remote process.

I doubt this is a good long-term plan.

IIRC there was some discussion on the last kvm forum on the idea to
re-use the vfio API for pci emulation in a separate process, i.e. create
something like vfio-user.  Have you considered this?

Sure, the lsi host adapter will probably need some refactoring so the
code can compiled into both qemu and a vfio-user server.  But that way
the chance that this can be maintained long-term without too much
headache is much higher.

A small, well-defined interface will also make it easier to re-write the
device emulation in another language like rust or go.

The current patch series feels more like a early proof-of-concept than
something mergeable ...

cheers,
  Gerd