Re: [Xen-devel] [PATCH RFC v2 07/12] x86: allow per-domain mappings without NX bit or with specific mfn

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.01.18 at 09:02, <jgross@xxxxxxxx> wrote:
> On 29/01/18 18:06, Jan Beulich wrote:
>>>>> On 22.01.18 at 13:32, <jgross@xxxxxxxx> wrote:
>>> --- a/xen/arch/x86/mm.c
>>> +++ b/xen/arch/x86/mm.c
>>> @@ -1568,7 +1568,7 @@ void init_xen_l4_slots(l4_pgentry_t *l4t, mfn_t l4mfn,
>>>  
>>>      /* Slot 260: Per-domain mappings (if applicable). */
>>>      l4t[l4_table_offset(PERDOMAIN_VIRT_START)] =
>>> -        d ? l4e_from_page(d->arch.perdomain_l3_pg, __PAGE_HYPERVISOR_RW)
>>> +        d ? l4e_from_page(d->arch.perdomain_l3_pg, __PAGE_HYPERVISOR)
>>>            : l4e_empty();
>>>  
>>>      /* Slot 261-: text/data/bss, RW M2P, vmap, frametable, directmap. */
>>> @@ -5269,7 +5269,7 @@ int create_perdomain_mapping(struct domain *d, 
>>> unsigned long va,
>>>          }
>>>          l2tab = __map_domain_page(pg);
>>>          clear_page(l2tab);
>>> -        l3tab[l3_table_offset(va)] = l3e_from_page(pg, 
>>> __PAGE_HYPERVISOR_RW);
>>> +        l3tab[l3_table_offset(va)] = l3e_from_page(pg, __PAGE_HYPERVISOR);
>>>      }
>>>      else
>>>          l2tab = map_l2t_from_l3e(l3tab[l3_table_offset(va)]);
>>> @@ -5311,7 +5311,7 @@ int create_perdomain_mapping(struct domain *d, 
>>> unsigned long va,
>>>                  l1tab = __map_domain_page(pg);
>>>              }
>>>              clear_page(l1tab);
>>> -            *pl2e = l2e_from_page(pg, __PAGE_HYPERVISOR_RW);
>>> +            *pl2e = l2e_from_page(pg, __PAGE_HYPERVISOR);
>> 
>> These changes (in the absence of the description saying otherwise)
>> leave open whether any of the per-domain mappings now suddenly
>> become executable.
> 
> Are you fine with me adding something like the following to the commit
> message:
> 
> As create_perdomain_mapping() creates L1 mappings with flags being
> __PAGE_HYPERVISOR_RW this won't change any of the current per domain
> mappings to become executable.

That would seem to be sufficient, yes.

Jan


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