Re: [Xen-devel] [PATCH v2 29/30] xen/x86: allow PVHv2 to perform foreign memory mappings

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.10.16 at 16:27, <george.dunlap@xxxxxxxxxx> wrote:
> On 10/10/16 15:21, Jan Beulich wrote:
>>>>> On 27.09.16 at 17:57, <roger.pau@xxxxxxxxxx> wrote:
>>> --- a/xen/arch/x86/mm/p2m.c
>>> +++ b/xen/arch/x86/mm/p2m.c
>>> @@ -2793,7 +2793,7 @@ int p2m_add_foreign(struct domain *tdom, unsigned 
>>> long fgfn,
>>>      struct domain *fdom;
>>>  
>>>      ASSERT(tdom);
>>> -    if ( foreigndom == DOMID_SELF || !is_pvh_domain(tdom) )
>>> +    if ( foreigndom == DOMID_SELF || !has_hvm_container_domain(tdom) )
>>>          return -EINVAL;
>> 
>> Can PV domains make it here? If not, dropping the predicate would
>> seem the better adjustment.
> 
> Is there any chance that in the future PV domains might accidentally get
> here because of some other changes in the future?  If so, leaving the
> predicate seems like a sensible precaution to reduce the risk of XSAs
> down the road, since we're doing a load of checking already anyway. ;-)

In which case I'd still prefer to extend the ASSERT() right ahead of
the if(). But you're the maintainer of this code, so you know best.

Jan


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