On 05.08.20 19:40, Paul Durrant wrote:
Hi Jan, Paul
-----Original Message-----
From: Jan Beulich <jbeul...@suse.com>
Sent: 05 August 2020 17:20
To: Oleksandr Tyshchenko <olekst...@gmail.com>; Paul Durrant <p...@xen.org>
Cc: xen-devel@lists.xenproject.org; Oleksandr Tyshchenko
<oleksandr_tyshche...@epam.com>; Andrew
Cooper <andrew.coop...@citrix.com>; George Dunlap <george.dun...@citrix.com>;
Ian Jackson
<ian.jack...@eu.citrix.com>; Julien Grall <jul...@xen.org>; Stefano Stabellini
<sstabell...@kernel.org>; Wei Liu <w...@xen.org>; Daniel De Graaf
<dgde...@tycho.nsa.gov>
Subject: Re: [RFC PATCH V1 07/12] A collection of tweaks to be able to run
emulator in driver domain
On 03.08.2020 20:21, Oleksandr Tyshchenko wrote:
From: Oleksandr Tyshchenko <oleksandr_tyshche...@epam.com>
Trying to run emulator in driver domain I ran into various issues
mostly policy-related. So this patch tries to resolve all them
plobably in a hackish way. I would like to get feedback how
to implement them properly as having an emulator in driver domain
is a completely valid use-case.
From going over the comments I can only derive you want to run
an emulator in a driver domain, which doesn't really make sense
to me. A driver domain has a different purpose after all. If
instead you mean it to be run in just some other domain (which
also isn't the domain controlling the target), then there may
be more infrastructure changes needed.
Paul - was/is your standalone ioreq server (demu?) able to run
in other than the domain controlling a guest?
Not something I've done yet, but it was always part of the idea so that we
could e.g. pass through a device to a dedicated domain and then run multiple
demu instances there to virtualize it for many domUs. (I'm thinking here of a
device that is not SR-IOV and hence would need some bespoke emulation code to
share it out).That dedicated domain would be termed the 'driver domain' simply
because it is running the device driver for the h/w that underpins the
emulation.
I may abuse "driver domain" terminology, but indeed in our use-case we
pass through a set of H/W devices to a dedicated domain which is running
the device drivers for that H/Ws. Our target system comprises a thin
Dom0 (without H/W devices at all), DomD (which owns most of the H/W
devices) and DomU which runs on virtual devices. This patch tries to
make changes at Xen side to be able run standalone ioreq server
(emulator) in that dedicated (driver?) domain. Actually the virtio-mmio
PoC is based on IOREQ/DM features and emulator (based on demu) acting as
a virtio-mmio backend. But it may be various use-cases for that (some
mediator for sharing specific H/W resource between Guests or custom PCI
emulator for example). If this is valid from Xen PoV I would be happy to
get feedback how to transform tweaks (hacks) in current patch into the
proper support.
--
Regards,
Oleksandr Tyshchenko
