At 03/14/2012 05:51 PM, Amit Shah Wrote: > On (Wed) 14 Mar 2012 [16:29:50], 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 start vm like this: >> qemu ...\ >> -device virtio-serial \ >> -chardev socket,path=/tmp/foo,server,nowait,id=foo \ >> -device virtserialport,chardev=foo,name=port1 ... > > This is sufficient. On the host, you can open /tmp/foo using a custom > program or nc (nc -U /tmp/foo). On the guest, you can just open > /dev/virtio-ports/port1 and read/write into it. I have two questions: 1. does it OK to open this device when the guest is panicked? 2. how to prevent the userspace's program using this device? Thanks Wen Congyang > > See the following links for more details. > > https://fedoraproject.org/wiki/Features/VirtioSerial#How_To_Test > http://www.linux-kvm.org/page/Virtio-serial_API > >> You said that there are too many channels. Does it mean /tmp/foo is a channel? > > You can have several such -device virtserialport. The -device part > describes what the guest will see. The -chardev part ties that to the > host-side part of the channel. > > /tmp/foo is the host end-point for the channel, in the example above, > and /dev/virtio-ports/port1 is the guest-side end-point. > > Amit > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
