On 03/14/2012 11:53 AM, Wen Congyang wrote: > At 03/14/2012 05:24 PM, Avi Kivity Wrote: > > On 03/14/2012 10:29 AM, Wen Congyang wrote: > >> At 03/13/2012 06:47 PM, Avi Kivity Wrote: > >>> On 03/13/2012 11:18 AM, Daniel P. Berrange wrote: > >>>> On Mon, Mar 12, 2012 at 12:33:33PM +0200, Avi Kivity wrote: > >>>>> On 03/12/2012 11:04 AM, Wen Congyang wrote: > >>>>>> Do you have any other comments about this patch? > >>>>>> > >>>>> > >>>>> Not really, but I'm not 100% convinced the patch is worthwhile. It's > >>>>> likely to only be used by Linux, which has kexec facilities, and you can > >>>>> put talk to management via virtio-serial and describe the crash in more > >>>>> details than a simple hypercall. > >>>> > >>>> As mentioned before, I don't think virtio-serial is a good fit for this. > >>>> We want something that is simple & guaranteed always available. Using > >>>> virtio-serial requires significant setup work on both the host and guest. > >>> > >>> So what? It needs to be done anyway for the guest agent. > >>> > >>>> Many management application won't know to make a vioserial device > >>>> available > >>>> to all guests they create. > >>> > >>> Then they won't know to deal with the panic event either. > >>> > >>>> Most administrators won't even configure kexec, > >>>> let alone virtio serial on top of it. > >>> > >>> It should be done by the OS vendor, not the individual admin. > >>> > >>>> The hypercall requires zero host > >>>> side config, and zero guest side config, which IMHO is what we need for > >>>> this feature. > >>> > >>> If it was this one feature, yes. But we keep getting more and more > >>> features like that and we bloat the hypervisor. There's a reason we > >>> have a host-to-guest channel, we should use it. > >>> > >> > >> I donot know how to use virtio-serial. > > > > I don't either, copying Amit. > > > >> I start vm like this: > >> qemu ...\ > >> -device virtio-serial \ > >> -chardev socket,path=/tmp/foo,server,nowait,id=foo \ > >> -device virtserialport,chardev=foo,name=port1 ... > >> > >> You said that there are too many channels. Does it mean /tmp/foo is a > >> channel? > > > > Probably. > > Hmm, if we use virtio-serial, the guest kernel writes something into the > channel when > the os is panicked. Is it right?
Right. > If so, is this channel visible to guest userspace? If the channle is visible > to guest > userspace, the program running in userspace may write the same message to the > channel. > Surely there's some kind of access control on channels. -- error compiling committee.c: too many arguments to function
