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Re: [libvirt] pvpanic device should not be automatically included as an internal device

On 08/02/2013 12:42 AM, Eric Blake wrote:
On 08/01/2013 04:23 PM, Paolo Bonzini wrote:
Automatic devices with no command line argument have proven to be a
nightmare for libvirt as well.  Although the just-released libvirt 1.1.1
now supports the <on_crash> element for controlling the command line
parameters of qemu related to how qemu will behave when the pvpanic
device is triggered, I would also welcome having the ability to control
whether the guest even has a pvpanic device exposed, just as we can
control whether a guest has a memballoon device exposed.

This is quite different from memballoon.

pvpanic is a single I/O port, it doesn't use up a PCI slot (thus
causing conflicts with other devices at the same address).

Perhaps this issue is simply fixed by making the _STA method
return 0x0B instead of 0x0F (i.e. turning off the "show in user
interface" bit).

That may "fix" the issue of a windows guest showing the yellow ! mark,
but what if, down the road, someone writes an actual windows driver that
is aware of that port and how to make a windows BSOD write a panic
notification to the port?  How does a user go about installing such a
driver if the device is not exposed in the user interface list of devices?

The user can still manually install a driver even for a device that is not exposed.

Having to manually specify the pvpanic device would be yet another knob that nobody uses. Panic notification is a useful feature that should be supported with no particular intervention from the user.


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