Re: [Xen-devel] [v6][PATCH 2/2] xen:vtd: missing RMRR mapping while share EPT

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.07.14 at 10:59, <tiejun.chen@xxxxxxxxx> wrote:
> On 2014/7/30 16:36, Jan Beulich wrote:
>>>>> On 30.07.14 at 03:36, <tiejun.chen@xxxxxxxxx> wrote:
>>> --- 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_identity_p2m_entry(d, base_pfn) )
>>> +                return -1;
>>> +        }
>>> +        else if ( intel_iommu_map_page(d, base_pfn, base_pfn,
>>> +                                       IOMMUF_readable|IOMMUF_writable) )
>>>               return -1;
>>>           base_pfn++;
>>>       }
>>
>> So I wonder how this plays together with
>>
>>      /* FIXME: Because USB RMRR conflicts with guest bios region,
>>       * ignore USB RMRR temporarily.
>>       */
>>      seg = pdev->seg;
>>      bus = pdev->bus;
>>      if ( is_usb_device(seg, bus, pdev->devfn) )
>>      {
>>          ret = 0;
>>          goto done;
>>      }
>>
>> later in the same file (in intel_iommu_assign_device()). I.e. the
>> improvement you claim won't be achieved for passed through USB
> 
> I think we can remove this chunk of codes since these two patches 
> already check if they conflicts.

Causing an apparent regression for anyone wanting to pass through
a USB devices associated with an RMRR? I agree this is the more
correct thing to do, but I'm not sure all our users would agree.

Jan


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