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

["Han, Weidong" <weidong.han@xxxxxxxxx>]

Jiang, Yunhong wrote:
>  One consideration to is to split them into two item:
> a) For all device that is not hot-pluged, we don't need this
> hypercall, instead, Xen will do the scan and setup the mapping. 
> b) For those hot-plug device and SR-IOV devices, maybe we can use the
> BUS_NOTIFY_ADD_DEVICE notifier to achieve ths purpose. We can just
> add a notifier to it. I assume this is simlar to IOMMU in kernel,
> which should requires this notify also. So a Xen specific notifier
> should achieve our purpose without change to the PCI bus layer.

This method looks good. It only needs to register a notifier call for Xen. It 
should be more possible to be accepted by upstream.

Regards,
Weidong
    
> 
> I checked the kernel code, and noticed that
> arch/x86/kernel/amd_iommu.c register the notifier for
> BUS_NOTIFY_ADD_DEVICE, but a bit strange why Intel IOMMU has no such
> support, do you know if VT-d in kernel support device hotplug
> already?   
> 
> Allen/Jeremy, any suggestion?
> 
> Thanks
> Yunhong Jiang
> 
>> -----Original Message-----
>> From: Kay, Allen M
>> Sent: 2009年7月18日 7:43
>> To: Jeremy Fitzhardinge; Han, Weidong
>> Cc: 'xen-devel@xxxxxxxxxxxxxxxxxxx'; 'Keir Fraser'; Jiang, Yunhong
>> Subject: RE: [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 callbacks
>> 
>> 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?
>> 
>> Thanks,
>>    J

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