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Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state |
Date: |
Thu, 22 Aug 2013 12:34:46 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130806 Thunderbird/17.0.8 |
On 08/22/13 11:19, Paolo Bonzini wrote:
> Il 22/08/2013 10:38, Laszlo Ersek ha scritto:
>>>> To support 1.5, libvirt should simply be ready to react to unanticipated
>>>> GUEST_PANICKED events. reboot-on-panic will simply be broken for 1.5
>>>> and Linux 3.10+ guests. :(
>> I'm probably misunderstanding the discussion, but it might be possible
>> to disable pvpanic even in 1.5 from the host side, with the following hack:
>>
>> -global pvpanic.ioport=0
>>
>> In qemu, this will either configure a working pvpanic device on ioport
>> 0, or the pvpanic device will be genuinely broken. At least it doesn't
>> (obviously) break other stuff (in v1.5.2):
>>
>> (qemu) info mtree
>> I/O
>> 0000000000000000-000000000000ffff (prio 0, RW): io
>> 0000000000000000-0000000000000000 (prio 0, RW): pvpanic
>> 0000000000000000-0000000000000007 (prio 0, RW): dma-chan
>
> No, you're not misunderstanding the discussion.
>
> Depending on the priorities of the pvpanic and legacy-DMA regions, it
> would break DMA channel 0.
<academic>
I think before priority comes into the picture, the access size would
matter first, no?
(I think I'm recalling this from the 0xCF9 reset control register, which
falls into the [0xCF8..0xCFA] range.)
Unless ioport 0 is accessed with width 1 for dma-chan purposes, I think
such an access would be unique to pvpanic, and always dispatched to pvpanic.
> Channel 0 is (was) used for DRAM refresh, so
> it should not have any visible effect. However, it may not be entirely
> disabling pvpanic, just making it mostly invisible.
That's good enough for the guest to reach kexec :)
</academic>
Laszlo
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, (continued)
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Michael S. Tsirkin, 2013/08/21
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Luiz Capitulino, 2013/08/21
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Eric Blake, 2013/08/21
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Paolo Bonzini, 2013/08/21
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Michael S. Tsirkin, 2013/08/21
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Laszlo Ersek, 2013/08/22
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Paolo Bonzini, 2013/08/22
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Michael S. Tsirkin, 2013/08/22
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Paolo Bonzini, 2013/08/22
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state,
Laszlo Ersek <=
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Laszlo Ersek, 2013/08/22
- Re: [Qemu-stable] [PATCH] vl: allow "cont" from panicked state, Paolo Bonzini, 2013/08/22