Re: Xen 4.2 and PCI hotplug.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Dec 19, 2012 at 08:47:58AM +0000, Jan Beulich wrote:
> >>> On 19.12.12 at 09:13, "Zhang, Xiantao" <xiantao.zhang@intel.com> wrote:
> > Are you playing with Xen ?  so far,  Xen doesn't support PCIe device hot-plug 
> > feature yet.
> 
> When saying Xen, I assume you mean the pv-ops kernel instead? So

I am looking at the PCI AER which can do native hotplug. And from
the Linux side it ought to work right -- but there is some scanning
of said new PCI device "before" the notifications are sent (which
we latch on and do the hypercall on). At least that is from a cursory
read of the code.

I presume that "before" the hypercall is sent Xen would just
ignore the 0xcf8 reads. But after the hypercall it would populate
appropiately whatever it needs. But it would never get to that point
b/c Linux couldn't read the device.

I might be of course completly off-base - hence asking if
Intel has done any sort of testing on this?

> far I was under the impression that this worked even with the very
> old 2.6.18 tree (as much or as little as hotplug there worked in the
> native case). And given that there are no special requirements on
> the hypervisor to make this work, it's not even obvious to me what
> would be missing in the pv-ops kernel to make it work.
> 
> All that is of course with me not having any practical experience
> with hotplug, due to the lack of capable hardware...
> 
> Jan
> 
>