Re: [PATCH v2 1/2] xen: introduce arch_iommu_grant_(un)map_page

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

On 24/07/14 12:07, Stefano Stabellini wrote:
> On Thu, 24 Jul 2014, Julien Grall wrote:
>> Hi Stefano,
>>
>> The Title of the commit message is now wrong.
>
> Thanks, I didn't notice.
>
>
>> On 23/07/14 18:19, Stefano Stabellini wrote:
>>> Introduce two arch specific functions to create a new p2m mapping of
>>> granted pages at pfn == mfn.
>>> The x86 implementation just returns ENOSYS.
>>>
>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>>> ---
>>>    xen/arch/arm/p2m.c        |   19 +++++++++++++++++++
>>>    xen/include/asm-arm/p2m.h |    4 ++++
>>>    xen/include/asm-x86/p2m.h |   13 +++++++++++++
>>>    3 files changed, 36 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
>>> index 9960e17..c38af59 100644
>>> --- a/xen/arch/arm/p2m.c
>>> +++ b/xen/arch/arm/p2m.c
>>> @@ -555,6 +555,25 @@ void guest_physmap_remove_page(struct domain *d,
>>>                          pfn_to_paddr(mfn), MATTR_MEM, p2m_invalid);
>>>    }
>>>
>>> +int arch_grant_map_page_identity(struct domain *d, unsigned long frame,
>>> +                                 bool_t writeable)
>>> +{
>>> +    p2m_type_t t;
>>> +
>>> +    if ( writeable )
>>> +        t = p2m_ram_rw;
>>> +    else
>>> +        t = p2m_ram_ro;
>>
>> This is not the right p2m type to use here. p2m_ram_{rw,ro} allow foreign
>> mapping. So another guest could access to the grant.
>>
>> I would use p2m_iommu_map_{rw,ro}.
>
>
> I see. I'll make the change and add a comment to explain why we are
> using p2m_iommu types for non-iommu related mappings.

The code to add the 1:1 mapping for the SMMU is very ugly. I was 
wondering if we could drop the iommu_map_page callback and
directly use arch_grant_map_page_identity in all the case.

It would avoid the if/else in the grant code.

Regards,

-- 
Julien Grall