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Re: [Qemu-devel] One question to lowlevel/xl/xl.c and lowlevel/xc/xc.c

From: Ian Campbell
Subject: Re: [Qemu-devel] One question to lowlevel/xl/xl.c and lowlevel/xc/xc.c
Date: Tue, 24 Mar 2015 09:51:44 +0000

On Tue, 2015-03-24 at 16:47 +0800, Chen, Tiejun wrote:
> All guys,
> Sorry to bother you.
> I have a question to two files, tools/python/xen/lowlevel/xc/xc.c and 
> tools/python/xen/lowlevel/xl/xl.c. Who is a caller to those methods like 
> pyxc_methods[] and pyxl_methods[]?

They are registered with the Python runtime, so they are called from
Python code. The first member of the struct is the pythonic function
name, e.g. from xc.c:
    { "domain_create", 
      "Create a new domain.\n"
      " dom    [int, 0]:        Domain identifier to use (allocated if zero).\n"
      "Returns: [int] new domain identifier; -1 on error.\n" },
defines a method called domain_create, in the xen.lowlevel.xc namespace.

>  And how should we call these approaches?

I'm not sure what you are asking here.

> In my specific case, I'm trying to introduce a new flag to each a device 
> while assigning device. So this means I have to add a parameter, 'flag', 
> into
> int xc_assign_device(
>      xc_interface *xch,
>      uint32_t domid,
>      uint32_t machine_sbdf)
> Then this is extended as
> int xc_assign_device(
>      xc_interface *xch,
>      uint32_t domid,
>      uint32_t machine_sbdf,
>      uint32_t flag)
> After this introduction, obviously I should cover all cases using 
> xc_assign_device(). And also I found this fallout goes into these two 
> files. For example, here pyxc_assign_device() is involved. Currently it 
> has two parameters, 'dom' and 'pci_str', and as I understand 'pci_str' 
> should represent all pci devices with SBDF format, right?

It appears so, yes.

> But I don't know exactly what rule should be complied to construct this 
> sort of flag into 'pci_str', or any reasonable idea to achieve my goal?

If it is non-trivial to fix them IMHO it is acceptable for the new
parameter to not be plumbed up to the Python bindings until someone
comes along with a requirement to use it from Python. IOW you can just
pass whatever the nop value is for the new argument.


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