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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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On Sat, 9 Aug 2014, manish jaggi wrote:
> On 1 August 2014 19:31, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> 
> wrote:
>       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:
> 
> That is working
> 
>       xen/arch/arm/platforms/xgene-storm.c:xgene_storm_specific_mapping
> 
> I believe that is a static mapping, we are passing the PCI node in device 
> tree moreover cavium pcie uses MSI.
> 
>       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).
> 
> Can you please elaborate more on this, does there needs to be some code which 
> is ARM specific in libxl

I don't see anything x86 specific in libxl_pci.c but the code hasn't
actually ever been run on Xen on ARM so I wouldn't be surprised if
you'll need to fix a few things to get it going.


>       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 Âspecific missing pieces, corresponding to the x86 ones in
>       arch/x86/pci/xen.c. They are mostly about MSIs.
> 
> 
> 
>

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