Re: One question to lowlevel/xl/xl.c and lowlevel/xc/xc.c

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2015/3/24 17:51, Ian Campbell wrote:
> On Tue, 2015-03-24 at 16:47 +0800, Chen, Tiejun wrote:
>> All guys,
>>

Thanks for your reply.

>> 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

Sorry I don't understanding this. So seems you mean instead of xl, this 
is called by the third party user with python?

> name, e.g. from xc.c:
>      { "domain_create",

Otherwise, often we always perform `xl create xxx' to create a VM. So I 
think this should go into this flow like this,

xl_cmdtable.c:main_create()
	|
	+ create_domain()
		|
		+ libxl_domain_create_new()
			|
			+ do_domain_create()
				|
				+ ....
Right?

>        (PyCFunction)pyxc_domain_create,

So I don't see 'pyxc_domain_create' is called. Or I'm missing something...

>        METH_VARARGS | METH_KEYWORDS, "\n"
>        "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.

If you can give a real case to call this, things couldn't be better :)

>
>> 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.
>

Should I extend this 'pci_str' like "Seg,bus,device,function:flag"? But 
I'm not sure if I'm breaking the existing usage since like I said, I 
don't know what scenarios are using these methods.

Thanks
Tiejun