Re: [Xen-devel] [PATCH v6 07/30] PCI: Pass PCI domain number combined with root bus number

[Yijing Wang <wangyijing@xxxxxxxxxx>]

On 2015/3/18 12:26, Manish Jaggi wrote:
> 
> On Tuesday 17 March 2015 07:35 PM, Ian Campbell wrote:
>> On Tue, 2015-03-17 at 10:45 +0530, Manish Jaggi wrote:
>>> On Monday 09 March 2015 08:04 AM, Yijing Wang wrote:
>>>> Now we could pass PCI domain combined with bus number
>>>> in u32 argu. Because in arm/arm64, PCI domain number
>>>> is assigned by pci_bus_assign_domain_nr(). So we leave
>>>> pci_scan_root_bus() and pci_create_root_bus() in arm/arm64
>>>> unchanged. A new function pci_host_assign_domain_nr()
>>>> will be introduced for arm/arm64 to assign domain number
>>>> in later patch.
>>> Hi,
>>> I think these changes might not be required. We have made very few
>>> changes in the xen-pcifront to support PCI passthrough in arm64.
>>> As per xen architecture for a domU only a single pci virtual bus is
>>> created and all passthrough devices are attached to it.
>> I guess you are only talking about the changes to xen-pcifront.c?
>> Otherwise you are ignoring the dom0 case which is exposed to the real
>> set of PCI root complexes and anyway I'm not sure how "not needed for
>> Xen domU" translates into not required, since it is clearly required for
>> other systems.
>>
>> Strictly speaking the Xen pciif protocol does support multiple buses,
>> it's just that the tools, and perhaps kernels, have not yet felt any
>> need to actually make use of that.
>>
>> There doesn't seem to be any harm in updating pcifront to follow this
>> generic API change.
> ok.
> 
> One side question, the function
> 
>  pci_host_assign_domain_nr()
> 
> which would be introduced in later patch, does it appear to be doing the same 
> binding which we are trying to implement via a pci_host_bridge add hypercall.

pci_host_assign_domain_nr() will be called only when CONFIG_PCI_DOMAINS_GENERIC 
enabled, now mostly be used in arm/arm64.

Thanks!
Yijing.

> 
>>
>> Ian.
>>
> 
> 
> 


-- 
Thanks!
Yijing


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