Re: [v3][PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT

["Chen, Tiejun" <tiejun.chen@intel.com>]

On 2014/7/24 19:11, Tim Deegan wrote:
> At 19:00 +0800 on 24 Jul (1406224818), Tiejun Chen wrote:
>> intel_iommu_map_page() does nothing if VT-d shares EPT page table.
>> So rmrr_identity_mapping() never create RMRR mapping but in some
>> cases like some GFX drivers it still need to access RMRR.
>>
>> Here we will create those RMRR mappings even in shared EPT case.
>>
>> Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
>
> For the interaction with p2m code:
>
> Acked-by: Tim Deegn <tim@xen.org>

Thanks a lot.

>
> though I am still worried about what happens if this overwrites an
> existing mapping.
>

As I understand RMRR should be specific. Its unlikely created for 
different mapping since this should be fixed in BIOS phase. And this is 
why that function is named as rmrr_identity_mapping().

Tiejun

> Tim.
>
>> ---
>>   xen/drivers/passthrough/vtd/iommu.c | 10 ++++++++--
>>   1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> v3:
>>
>> * Use set_mmio_p2m_entry() to replace p2m_set_entry()
>> * Use ASSERT to check
>>
>> v2:
>>
>> * Fix coding style.
>> * Still need to abide intel_iommu_map_page(), so we should do nothing
>>    if dom0 and iommu supports pass thru.
>>
>> diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
>> index 042b882..f08a1fc 100644
>> --- a/xen/drivers/passthrough/vtd/iommu.c
>> +++ b/xen/drivers/passthrough/vtd/iommu.c
>> @@ -1867,8 +1867,14 @@ static int rmrr_identity_mapping(struct domain *d,
>>
>>       while ( base_pfn < end_pfn )
>>       {
>> -        if ( intel_iommu_map_page(d, base_pfn, base_pfn,
>> -                                  IOMMUF_readable|IOMMUF_writable) )
>> +        if ( iommu_use_hap_pt(d) )
>> +        {
>> +            ASSERT(!iommu_passthrough || !is_hardware_domain(d));
>> +            if ( set_mmio_p2m_entry(d, base_pfn, _mfn(base_pfn)) )
>> +                return -1;
>> +        }
>> +        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
>> +                                       IOMMUF_readable|IOMMUF_writable) )
>>               return -1;
>>           base_pfn++;
>>       }
>> --
>> 1.9.1
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org
>> http://lists.xen.org/xen-devel
>
>