[vfio-users] hot-plug PCIe reassignment

[Ryan Flagler]

This is interesting. The Microsoft Surface book has a dgpu in the keyboard
that can be attached/detached at will. Could be a combination of
proprietary hardware/software though.

On Fri, Jul 8, 2016, 9:53 PM Alex Williamson <alex.l.williamson at gmail.com>
wrote:

> On Fri, Jul 8, 2016 at 8:43 PM, Kajim Shanti <kajimshanti at gmail.com>
> wrote:
>
>> Hi,
>> Since I heard there are some PCIe devices that are hot-pluggable, I was
>> wondering if it might work to cut off the power from a discrete graphic
>> card in order to reassign it among different VMs without having to restart
>> the host (and possibly the guests too?) Has anyone tried yet? Might it help
>> to get a secondary PSU so that one could easily power on and off his
>> descrete graphics without having to open the case? Thank you, sorry if the
>> question was asked already.
>>
>
> Why would you need to cut power to the device to reassign it?  The
> limitation here is guest drivers, the bus reset we do is already sufficient
> for hot-plugging between guests, unless you've made the mistake of buying
> AMD.  AFAIK, Windows already supports both hot unplug and re-plug, but
> seems to require a guest reboot to really activate a hot-added GPU.  I
> don't know if I've tested this on win10 though, maybe it's improved.
> Anyway, a secondary PSU is probably only going to allow you to put the card
> into a broken state where the GPU is still powered by the slot, but doesn't
> have the additional external power.  Seems like a non-zero chance of
> letting out the magic smoke doing something like that too.
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