Re: xentrace, arm, hvm

[Julien Grall <julien.grall@linaro.org>]

On 08/02/14 15:51, Pavlo Suikov wrote:
> Hi,

Hi Pavlo,

>>
>> >  > To support xentrace on ARM, we will need at least:
>> >
>> > I would readily do that if you give me some directions on where to look
>> > at, or a high-level explanation of:
>> >
>> >  > - to replace rcu_lock_domain_by_any_id() by a a similar function
>> >
>> > What semantics should this function have?
>>
>> I would copy in part get_pg_owner (arch/x86/mm/mm.c) in the ARM code.
>> The check "unlikely(paging_mode_translate(curr))" will always fail on ARM.
>
>> Probably best just todig in and ask questions as issues arise.
>
> After making a quick workaround to rcu_lock DOMAIN_XEN on arm (in the
> quite same manner it is done in x86) I've faced different problem.
> Specifically, p2m_lookup for an address in the xen restricted heap fails
> on the very first map call: p2m_map_first returns zero page due to both
> p2m->first_level and p2m_first_level_index(addr) equal to zero. As far
> as I understand xen simply does not know how to make p2m translation for
> it's own restricted heap on arm. Am I right?

For DOMID_XEN, the p2m is not initialized. When xentrace requests to map 
a page by directly giving the mfn (machine frame number), so there is no 
need of translation.

I would either add a specific case for DOMID_XEN in get_page_from_gfn or 
p2m_lookup.

Regards,

-- 
Julien Grall