[libvirt] (no subject)
Daniel P. Berrange
berrange at redhat.com
Wed Dec 7 09:16:27 UTC 2011
On Wed, Dec 07, 2011 at 08:21:06AM +0200, Sasha Levin wrote:
> On Tue, 2011-12-06 at 14:38 +0000, Daniel P. Berrange wrote:
> > On Fri, Nov 11, 2011 at 07:56:58PM +0800, Osier Yang wrote:
> > > * KVM tool manages the network completely itself (with DHCP support?),
> > > no way to configure, except specify the modes (user|tap|none). I
> > > have not test it yet, but it should need explicit script to setup
> > > the network rules(e.g. NAT) for the guest access outside world.
> > > Anyway, there is no way for libvirt to control the guest network.
> > If KVM tool support TAP devices, can't be do whatever we like with
> > that just by passing in a configured TAP device from libvir ?
> KVM tool currently creates and configures the TAP devices it uses, it
> shouldn't be an issue to have it use a TAP fd passed to it either.
> How does libvirt do it? Create a /dev/tapX on it's own and pass the fd
> to the hypervisor?
Yes, libvirt opens a /dev/tap device (or a macvtap device for VEPA
mode), adds it to the neccessary bridge, and/or configures VEPA, etc
and then passes the FD to the hypervisor, with a ARGV parameter to
tell the HV which FD is being passed.
> > > * console connection is implemented by setup ptys in libvirt, stdout/stderr
> > > of kvm tool process is redirected to the master pty, and libvirt connects
> > > to the slave pty. This works fine now, but it might be better if kvm
> > > tool could provide more advanced console mechanisms. Just like QEMU
> > > does?
> > This sounds good enough for now.
> KVM tools does a redirection to a PTY, which at that point could be
> redirected to anywhere the user wants.
> What features might be interesting to do on top of that?
I presume that Osier is just comparing with the features QEMU has available
for chardevs config, which include
- UNIX sockets
- TCP sockets
- UDP sockets
- FIFO pipe
- Plain file (output only obviously, but useful for logging)
libvirt doesn't specifically need any of them, but it can support those
options if they exist.
> > > * Not much ways existed yet for external apps or user to query the guest
> > > informations. But this might be changed soon per KVM tool grows up
> > > quickly.
> > What sort of guest info are you thinking about ? The most immediate
> > pieces of info I can imagine we need are
> > - Mapping between PIDs and vCPU threads
> > - Current balloon driver value
> Those are pretty easily added using the IPC interface I've mentioned
> above. For example, 'kvm balloon' and 'kvm stat' will return a lot of
> info out of the balloon driver (including the memory stats VQ - which
> afaik we're probably the only ones who actually do that (but I might be
> wrong) :)
Ok, that sounds sufficient for the balloon info.
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