Re: [Xen-users] UEFI Booting

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2015-04-01 at 10:58 -0300, Carlos Gustavo Ramirez Rodriguez wrote:

> Sure, I am glad to be able help! What should I read to better
> understand this PCI-PHANTOM problem as a whole, so that I can send a
> working and non-"half baked" code?

I don't know, I know very little about the phantom stuff myself, but I
don't think you need to understand it as a whole, just the quirks
infrastructure.

> I noticed the instruction pci-phantom used in the "command-line" of
> xen, where can I find the hierarchy of xen functions to know where
> they can be used and from where are they being called? Is there a
> graphical version? What is the faster way I can understand all of
> these questions to code as fast as possible a solution?

I usually answer such questions using tools like grep and find or cscope
or by reading the code. You can edit the code with whichever editor you
feel most comfortable with, there is no one graphical IDE for Xen
development.

In this case most of the code you need to look at is in
xen/drivers/passthrough/pci.c, the command line option is handled by
parse_phantom_dev which is referenced by custom_param (right after the
function) and adds an entry to the phantom_devs array (just above).

The code which then looks at that array is in alloc_pdev, where it loops
over the array checking if the new device is one of the ones given on
the command line.

I think you would want to refactor that checking loop into a new
function (check_phantom_dev_quirk?) which as well as looking at the list
as the code does today also reads the device's PCI vendor and device ID
and if they match a known broken device (starting with your one) then
apply the appropriate phantom_stride.

That's what I would do at least, the people who maintain the code may
disagree or have a better idea.

Once you have a patch you should read
http://wiki.xenproject.org/wiki/Submitting_Xen_Patches which gives some
general hints about the patch submission process.

Is that enough to be going on?

Ian.


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