Re: [PATCH] libxc: Add xc_domain_hvm_get_mtrr_type() call

[Razvan Cojocaru <rzvncj@gmail.com>]

Thanks for the reply!

> Do you have a user in mind for this new functionality?

Yes. An (userspace) application that needs to look at this information 
to decide if a set of pages are interesting for monitoring.

> This version seems to do a lot less than get_mtrr_type() in the
> hypervisor. Is that deliberate? Why isn't the fixed mtrr slot and
> overlap handling required here?

It does do less. It's somewhat deliberate :), ideally it should have 
done everything that get_mtrr_type() does. It did work with my initial 
test addresses, but clearly more is required if it is to provide the 
full functionality of get_mtrr_type(). The code currently only iterates 
through the var_ranges, not the fixed array, etc.

The overlap handling isn't there because there doesn't seem to be a 
clear correspondence between struct mtrr_state and  struct hvm_hw_mtrr. 
I implemented as much of the get_mtrr_type() logic as was obvious using 
what mapping was clear bewtween them.

Is having the full functionality in libxc feasible?

>>   /**
>> + * This function returns information about the MTRR type of
>> + * a given guest physical address/
>
>                                     ^ you mean . not / I think.

You're right, sorry for the typo.

Thanks,
Razvan Cojocaru