Re: pyxc_linux_build() in tools/python/xen/lowlevel/xc/xc.c still needed?

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/10/15 10:11, Roger Pau Monné wrote:
> El 06/10/15 a les 10.56, Ian Campbell ha escrit:
>> On Tue, 2015-10-06 at 08:33 +0200, Juergen Gross wrote:
>>> Do we have any requirements to be compatible to old releases regarding
>>> the functions in tools/python/xen/lowlevel/xc/xc.c ?
>> IMHO, no.
>>
>> There are also too many compatibility shims in front of the domain builder,
>> i.e. all the stuff in tools/libxc/xc_dom_compat_linux.c which IMHO could be
>> nuked too.
>>
>>> Especially pyxc_linux_build() isn't used anywhere in the tree. And this
>>> is the only function setting xc_dom_image.superpages, thus removing it
>>> would give us the chance to remove some code of the domain builder.
>> Right. 
>>
>> Removing the superpages option from the non-Python might cause concern for
>> some. Adding Konrad since IIRC PV superpages is a thing Oracle implemented
>> and might still care about.
>>
>> Also adding Roger since he is reworking the HVM builder to use the PV one,
>> which for all I know might involve using the superpage option (but probably
>> not the PV code to set it up).
> The superpages field is only used to populate memory of PV domains,
> AFAICT HVM domains will already try to use superpages by default in
> order to fill the p2m. I don't have any problem with it being removed.

There is a key difference between PV guests and HVM guests when it comes
to superpages.

A PV guest needs to be explicitly capable of handling superpages, and it
rules out things like migrate, etc.

HVM superpages are just EPT/NPT superpages, without a direct effect on
guest.

I don't object to removing this field, but mistakenly equate PV and HVM
guests in this regard.

~Andrew