On Fri, Aug 02, 2013 at 10:31:11AM +0200, Paolo Bonzini wrote:
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.
Yep, that was the big motivation behind doing it as an I/O port that we
could have enabled by default, as opposed to a virtio serial device or
some other paravirt device that required explicit configuration.
Daniel
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