Re: [libvirt] discuss about pvpanic
On 08/01/20 09:25, zhenwei pi wrote:
Hey, Paolo
Currently, pvpapic only supports bit 0(PVPANIC_PANICKED).
We usually expect that guest writes ioport (typical 0x505) in panic_notifier_list
callback
during handling panic, then we can handle pvpapic event PVPANIC_PANICKED in QEMU.
On the other hand, guest wants to handle the crash by kdump-tools, and reboots without
any
panic_notifier_list callback. So QEMU only knows that guest has rebooted (because guest
write 0xcf9 ioport for RCR request), but QEMU can't identify why guest resets.
In production environment, we hit about 100+ guest reboot event everyday, sadly we
can't separate the abnormal reboot from normal operation.
We want to add a new bit for pvpanic event(maybe PVPANIC_CRASHLOADED) to represent the
guest has crashed,
and the panic is handled by the guest kernel. (here is the previous patch
https://lkml.org/lkml/2019/12/14/265)
What do you think about this solution? Or do you have any other suggestions?
Hi Zhenwei,
the kernel-side patch certainly makes sense. I assume that you want the
event to propagate up from QEMU to Libvirt and so on? The QEMU patch
would need to declare a new event (qapi/misc.json) and send it in
handle_event (hw/misc/pvpanic.c). For Libvirt I'm not familiar, so I'm
adding the respective list.
Another possibility is to simply not write to pvpanic if
kexec_crash_loaded() returns true; this would match what xen_panic_event
does for example. The kexec kernel would then log the panic normally,
without the need for MMIO at all. However, I have no problem with
adding a new bit to the pvpanic I/O port so once you post the QEMU patch
I will certainly ack the kernel side.
Thanks,
Paolo