[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: discuss about pvpanic
From: |
Paolo Bonzini |
Subject: |
Re: discuss about pvpanic |
Date: |
Wed, 8 Jan 2020 10:36:56 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
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