On Wed, Mar 21, 2012 at 05:35:49PM +0800, Wen Congyang wrote: > At 03/21/2012 05:11 PM, Gleb Natapov Wrote: > > On Wed, Mar 21, 2012 at 08:56:03AM +0800, Wen Congyang wrote: > >> At 03/20/2012 11:45 PM, Gleb Natapov Wrote: > >>> On Tue, Mar 20, 2012 at 05:59:16PM +0800, Wen Congyang wrote: > >>>> At 03/19/2012 03:33 PM, Wen Congyang Wrote: > >>>>> At 03/08/2012 03:57 PM, Wen Congyang Wrote: > >>>>>> We can know the guest is paniced when the guest runs on xen. > >>>>>> But we do not have such feature on kvm. > >>>>>> > >>>>>> Another purpose of this feature is: management app(for example: > >>>>>> libvirt) can do auto dump when the guest is crashed. If management > >>>>>> app does not do auto dump, the guest's user can do dump by hand if > >>>>>> he sees the guest is paniced. > >>>>>> > >>>>>> I touch the hypervisor instead of using virtio-serial, because > >>>>>> 1. it is simple > >>>>>> 2. the virtio-serial is an optional device, and the guest may > >>>>>> not have such device. > >>>>>> > >>>>>> Changes from v2 to v3: > >>>>>> 1. correct spelling > >>>>>> > >>>>>> Changes from v1 to v2: > >>>>>> 1. split up host and guest-side changes > >>>>>> 2. introduce new request flag to avoid changing return values. > >>>>>> -- > >>>>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > >>>>>> the body of a message to majordomo@xxxxxxxxxxxxxxx > >>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html > >>>>>> Please read the FAQ at http://www.tux.org/lkml/ > >>>>>> > >>>>> > >>>>> > >>>>> Hi all: > >>>>> > >>>>> we neet this feature, but we don't decide how to implement it. > >>>>> We have two solution: > >>>>> 1. use vmcall > >>>>> 2. use virtio-serial. > >>>>> > >>>>> I will not change this patch set before we decide how to do it. > >>>>> Can we make a decision recent days? > >>>> > >>>> Anybody can decide which solution to use? > >>>> > >>> To make an informed decision we need to have at least raw idea how > >>> virtio-serial variant will look. > >> > >> Hmm, I think we can do this: > >> 1. reset the virtio-serial device or reset the port we use to notice > >> the host that guest is panicked. > >> 2. write some specific messages to the port > >> > >> So the port should have fixed name. If this port is opened by the userspace > >> before the guest is paniced, I am not sure whether we can use it(because a > >> port only can be opened once at the same time). > > Yes, IMO we should dedicate one virtio-serial port for panic > > notifications. Just like we dedicate one for a console. > > > >> We cannot call any function in the module, so we may need to write a simple > >> driver for virtio-serial(like diskdump's disk driver). > >> > > netconsole uses standard NIC drivers in polling mode to send OOPSes > > over the network and it mostly works. So I think using virtio-serial > > driver is not out of question, but with IRQ disabled of course. > > The code for netconsole is in which file? drivers/net/netconsole.c naturally. > Another question: we cannot call the function in the module directly in the > kernel. True I think. netconsole and actual NIC driver have a layer of abstraction between them. Modules can call functions from other modules. Your module can register to panic_notifier_list (like IPMI does) and call functions from virtio-serial. Or panic handling can be added directly to virtio-serial since it will have to be modified anyway. Something like netpoll API will have to be added to it. > > > >> I donot know how to implement it now. But I guess that it may be complicated. > >> > > Look at drivers/char/ipmi/ipmi_msghandler.c. It has code to send panic > > event over IMPI. The code is pretty complex. Of course if we a going to > > implement something more complex than simple hypercall for panic > > notification we better do something more interesting with it than just > > saying "panic happened", like sending stack traces on all cpus for > > instance. > > If we implement it by virtio-serial, I agree with passing more useful message > to host. > -- Gleb. -- 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
