Re: [Xen-devel] [Query] Assigning PCI ranges to dom0 and domU

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 1 Aug 2014, manish jaggi wrote:
> Hi Stefano,
> 
> I am working on accessing PCI nodes in the doms on ARM (cavium). If there is 
> the below device tree nodeÂ
> pcie1@0x849000000000 {
> ÂÂÂ ÂÂÂÂÂÂÂ compatible = "cavium,thunder-pcie";
> ÂÂÂ ÂÂÂ device_type = "pci";
> ÂÂÂ ÂÂÂ msi-parent = <&its>;
> ÂÂÂ ÂÂÂ bus-range = <0 255>;
> ÂÂÂ ÂÂÂ #size-cells = <2>;
> ÂÂÂ ÂÂÂ #address-cells = <3>;
> ÂÂÂÂÂÂÂ ÂÂÂ reg = <0x8490 0x00000000 0 0x40000000>;Â /* Configuration space */
> ÂÂÂ ÂÂÂ ranges = <0x03000000 0x8310 0x00000000 0x8310 0x00000000 0x00 
> 0x10000000>, /* mem ranges */
> ÂÂÂ ÂÂÂ ÂÂÂ <0x03000000 0x8100 0x00000000 0x8100 0x00000000 0x80 0x00000000>;
> ÂÂÂÂÂÂÂ };
> ÂÂÂ
> 
> How to assign ranges to guest dom0 / domU. Is there a well defined api in xen 
> OR I have to parse the device tree
> ranges and do a 1:1 mapping using map_mmio_regions.

Firstly you just need to get PCI up and running in Dom0, and you can do
that by passing this device tree node to Dom0 and remapping the
appropriate memory ranges. See for example:

xen/arch/arm/platforms/xgene-storm.c:xgene_storm_specific_mapping


Once that is done, it is time to look at pciback and pcifront and try to
get them running on ARM.


I would start by enabling PCI passthrough in the xl toolstack, look at
tools/libxl/libxl_pci.c:libxl__device_pci_add, called by
domcreate_attach_pci. It should be working on ARM following the PV path
(LIBXL_DOMAIN_TYPE_PV).


After the toolstack parts are in place, you should be able to see a pci
entry in xenstore (xenstore-ls to list everything that is present in
xenstore). That is the basic information needed by pcifront and pciback
to enstablish a communication channel. Pcifront is
drivers/pci/xen-pcifront.c and pciback is drivers/xen/xen-pciback: you
need to compile and initialize them on ARM. You might have to implement
a few ARM  specific missing pieces, corresponding to the x86 ones in
arch/x86/pci/xen.c. They are mostly about MSIs.

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