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RE: [Xen-devel] [pvops-dom0] [patch] Hook Linux's PCI probe and remove c

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "Han, Weidong" <weidong.han@xxxxxxxxx>
Subject: RE: [Xen-devel] [pvops-dom0] [patch] Hook Linux's PCI probe and remove callbacks
From: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
Date: Fri, 17 Jul 2009 16:42:39 -0700
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Cc: 'Keir, "'xen-devel@xxxxxxxxxxxxxxxxxxx'" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Fraser' <Keir.Fraser@xxxxxxxxxxxxx>, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>
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Thread-topic: [Xen-devel] [pvops-dom0] [patch] Hook Linux's PCI probe and remove callbacks
These hooks for two purposes:

1) Enabling of a SR-IOV virtual function.  The hypercall will tell xen to setup 
VT-d context entries for the BDF corresponding to the new virtual function.  
This is required for SR-IOV to work.

2) PCI hot-plug support when devices are hot added/removed.  Vt-d context 
entries and data structures in Xen needs to be modified accordingly.

These hooks needs to be enabled before either of these functions are performed 
- I assume after dom0 boots.

Can you suggest a better way to do this?

-----Original Message-----
From: Jeremy Fitzhardinge [mailto:jeremy@xxxxxxxx] 
Sent: Friday, July 17, 2009 4:14 PM
To: Han, Weidong
Cc: 'xen-devel@xxxxxxxxxxxxxxxxxxx'; 'Keir Fraser'; Kay, Allen M; Jiang, Yunhong
Subject: Re: [Xen-devel] [pvops-dom0] [patch] Hook Linux's PCI probe and remove 

On 07/15/09 22:15, Han, Weidong wrote:
> Hijack the pci_bus_type probe and remove callbacks. This option only
> requires modification to the Xen specific part of Linux.
> This is useful to add and remove pci device to Xen hypervisor when
> load and remove its driver. For example, when VFs are created by PF,
> they will be added to Xen hypervisor, and then can be assigned to guest.
> This patch is based on xen-tip-master branch of jeremy's pv-ops tree.

Yunhong Jiang sent me a version of this patch as part of his MSI work. 
This kind of interception of pci_bus_type.probe is pretty ugly, and is
unlikely to be accepted upstream in this form (the patch may only touch
a Xen file, but it is changing a variable belonging to the PCI
subsystem).  We need to work with the Linux PCI maintainers to find some
other way of achieving what we need here.

Can you explain what the functional requirements are here.  Could we
defer registering the device with Xen until some other convenient hook,
or must it be done at this point in the code?


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