Re: [Qemu-devel] pvpanic plans?

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 31, 2013 at 03:39:17PM +0100, Paolo Bonzini wrote:
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> Il 31/10/2013 15:32, Eric Blake ha scritto:
> > On 10/31/2013 08:30 AM, Michael S. Tsirkin wrote:
> >> On Thu, Oct 24, 2013 at 10:39:03AM +0800, Hu Tao wrote:
> >>> Hi All,
> >>> 
> >>> I know it's been a long time since this thread. But qemu 1.7 is
> >>> releasing, do you have any consensus on this?
> >> 
> >> I think the biggest issue is the new PANICKED state. Guests 
> >> already have simple ways to halt the CPU, and actually do.  I 
> >> think a new state was a mistake. So how about the following?
> >> Does it break anything? (Untested).
> > 
> > Don't you still need to halt the guest on a panic event, for 
> > management to have a chance to choose what to do about the panic? 
> > I'm suspecting this patch does break things.
> 
> Yes, it does.

What does it break exactly?

> But I think that, once we make the pvpanic device is
> optional, to a large extent there is no bug.  Adding the pvpanic
> device to the VM will make libvirt obey <oncrash> instead of the
> in-guest setting, and that's it.
> 
> Two months have passed and no casualties have been reported due to
> pvpanic.  Let's just remove the auto-pvpanic from all machine types in
> 1.7 (yes, that's backwards incompatible in a strict sense), document
> it in the release notes, and hope that the old QEMU versions with
> mandatory pvpanic die of old age.

Nod. I'm fine with that.

> All the advantages/disadvantages from my original messages still
> apply.  Let's ignore the disadvantages and just KISS.
> 
> Paolo

I think we still need to do get rid of the PANICKED state somehow.
If we can't replace it with RUNNING state, let's replace it with PAUSED.

For example, you can't continue from panicked for some reason.
You can't do a reset.
But you can pause and then continue.


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