Hi, On Fri, 2019-09-06 at 10:22 -0400, Michael S. Tsirkin wrote: > On Fri, Sep 06, 2019 at 03:13:50PM +0300, Johannes Berg wrote: > > From: Johannes Berg <johannes.b...@intel.com> > > > > Signed-off-by: Johannes Berg <johannes.b...@intel.com> > > a bit more content here about the motivation for this?
Heh, right, definitely needed. I was just sending it out as the corresponding patch to the spec change RFC, where I explained more, so didn't really bother here yet. However, I evidently forgot to CC you on that: https://lore.kernel.org/qemu-devel/20190902121233.13382-1-johan...@sipsolutions.net/ I'm still trying to implement it in User-Mode Linux (UML, ARCH=um), we've submitted patches for virtio/vhost-user support to that, but the simulation-bound IRQ handling is a bit complicated. I need to see how it turns out once I actually get it to work - I've gotten this extension, SLAVE_REQ and REPLY_ACK to work now, so need to "just" integrate with the time-travel mode I already have. In any case, if you think that this is a stupid extension and say you will never accept it, I'll probably just implement a slightly more hackish way, setting vhost-user to polling mode and using out-of-band signalling or so. This seems a bit cleaner though, and if it's properly spec'ed and with sample code and all then it'll possibly be far more useful to others. (**) I think I also forgot to CC you on these two: https://lore.kernel.org/qemu-devel/20190828083401.2342-1-johan...@sipsolutions.net/ https://lore.kernel.org/qemu-devel/20190903192505.10686-1-johan...@sipsolutions.net/ Again, sorry about that. Btw, at least one of these files doesn't even have an entry in the maintainers file. Don't remember if it was the spec though or the libvhost-user stuff. (**) For example, there's the VMSimInt paper (***) that shows a very similar thing with QEMU, but works only with CPU emulation. With UML's time-travel mode made to work over virtio we can do similar things without CPU emulation. I suspect it's also possible to emulate the HPET or so in a KVM-based system, but seems far more tricky (to me at least). (***) http://www.ikr.uni-stuttgart.de/Content/Publications/Archive/We_SIMUTools_2014_40209.pdf Thanks, johannes
