Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.03.15 at 06:26, <mjaggi@xxxxxxxxxxxxxxxxxx> wrote:
> In drivers/xen/pci.c on notification BUS_NOTIFY_ADD_DEVICE dom0 issues a 
> hypercall to inform xen that a new pci device has been added.
> If we were to inform xen about a new pci bus that is added there are  2 ways
> a) Issue the hypercall from drivers/pci/probe.c
> b) When a new device is found (BUS_NOTIFY_ADD_DEVICE) issue 
> PHYSDEVOP_pci_device_add hypercall to xen, if xen does not finds that 
> segment number (s_bdf), it will return an error
> SEG_NO_NOT_FOUND. After that the linux xen code could issue the 
> PHYSDEVOP_pci_host_bridge_add hypercall.
> 
> I think (b) can be done with minimal code changes. What do you think ?

I'm pretty sure (a) would even be refused by the maintainers, unless
there already is a notification being sent. As to (b) - kernel code could
keep track of which segment/bus pairs it informed Xen about, and
hence wouldn't even need to wait for an error to be returned from
the device-add request (which in your proposal would need to be re-
issued after the host-bridge-add).

Jan


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