At 10/10/2011 03:48 PM, Jan Kiszka Write: > On 2011-10-10 09:47, Wen Congyang wrote: >> At 10/10/2011 03:22 PM, Jan Kiszka Write: >>> On 2011-10-10 09:17, Wen Congyang wrote: >>>> At 10/10/2011 03:01 PM, Jan Kiszka Write: >>>>> On 2011-10-10 08:59, Wen Congyang wrote: >>>>>> At 10/10/2011 02:52 PM, Jan Kiszka Write: >>>>>>> On 2011-10-10 04:21, Wen Congyang wrote: >>>>>>>> At 10/09/2011 06:23 PM, Richard W.M. Jones Write: >>>>>>>>> On Sun, Oct 09, 2011 at 10:49:57AM +0200, Jan Kiszka wrote: >>>>>>>>>> As explained in the other replies: It is way more future-proof to >>>>>>>>>> use an >>>>>>>>>> interface for this which was designed for it (remote gdb) instead of >>>>>>>>>> artificially relaxing reasonable constraints of the migration >>>>>>>>>> mechanism >>>>>>>>>> plus having to follow that format with the post-processing tool. >>>>>>>>> >>>>>>>>> Any interface that isn't "get this information off my production >>>>>>>>> server *now*" so that I can get the server restarted, and send it to >>>>>>>>> an expert to analyse -- is a poor interface, whether it was designed >>>>>>>>> like that or not. Perhaps we don't have the right interface at all, >>>>>>>>> but remote gdb is not it. >>>>>>>> >>>>>>>> What about the following idea? >>>>>>>> >>>>>>>> Introduce a new monitor command named dump, and this command accepts a >>>>>>>> filename. >>>>>>>> We can use almost all migration's code. We use this command to dump >>>>>>>> guest's >>>>>>>> memory, so there is no need to check whether the guest has a >>>>>>>> unmigratable device. >>>>>>> >>>>>>> I do not want to reject this proposal categorically, but I would like to >>>>>>> see the gdb path fail /wrt essential requirements first. So far I don't >>>>>>> see it would. >>>>>> >>>>>> ‘gdb path fail /wrt essential requirements’ >>>>>> >>>>>> what does it mean? >>>>> >>>>> That you explain why reading reading memory and processor states via the >>>>> remote gdb interface and dumping it into a proper core file cannot be >>>>> made working for you. >>>> >>>> First, I think crash can not analyze such core file. But it is not very >>>> important. >>>> >>>> What is remote gdb interface? >>> >>> man qemu -> gdb. >>> >>>> Do you mean that: the supporter uses gdb from another machine >>> >>> Or locally. There are various transports possible. >>> >>>> to connect to customer's machine and get the data? If so, this way can not >>>> be >>>> used when the customer needs to dump the guest's memory automatically when >>>> watchdog timeouts. >>> >>> It is just another channel that can conceptually be used like the >>> monitor, by a management app like libvirt, directly or indirectly via a >>> scripted gdb frontend, or also by a human who wants to save some ongoing >>> gdb session for later analysis. This dual use make such an approach the >>> preferred one. >> >> Is the following is right? >> >> 1. execute the monitor command 'gdbserver' >> 2. run gdb and then 'target remote :1234' > > Yep.
Can two guest use such port(1234) at the same time? If not, I think qemu should support to select a port automatically. Another problem is that: we should not require dev and debug tools(here is gdb) to be installed on the production host. > >> >> But, unfortunately, the monitor command gdbserver does not exit when we use >> json to connect to monitor. > > You mean via human-monitor-command (gdbserver is not a qmp command)? Yes. Thanks Wen Congyang > Would be a bug. > > Jan >
