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

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

On 2014/9/22 16:53, Jan Beulich wrote:
>>>> On 22.09.14 at 07:46, <tiejun.chen@intel.com> wrote:
>>>    >> It should suffice to give 3 Gb (or event slightly less) of memory to
>>>   >> the DomU (if your Dom0 can hopefully tolerate running with just 1Gb).
>>>   >
>>>   > Yes. So I can't produce that real case of conflict with those existing
>>>   > RMRR in my platform.
>>>
>>> When you pass 3Gb to the guest, its memory map should extend to
>>> about 0xC0000000, well beyond the range the RMRRs reference. So
>>
>> Yes. So I set memory size as 2816M which also cover all RMRR ranges in
>> my platform.
>>
>>> you ought to be able to see the collision (or if you don't you ought to
>>> have ways to find out why they're not happening, as that would be a
>>> sign of something else being bogus).
>>>
>>
>> Then I can see that work as we expect:
>>
>> # xl cr hvm.cfg
>> Parsing config from hvm.cfg
>> libxl: error: libxl_pci.c:949:do_pci_add: xc_assign_device failed:
>> Operation not permitted
>> libxl: error: libxl_create.c:1329:domcreate_attach_pci:
>> libxl_device_pci_add failed: -3
>>
>> And
>>
>> # xl dmesg
>> ...
>> (XEN) [VT-D]iommu.c:1589: d0:PCI: unmap 0000:00:02.0
>> (XEN) [VT-D]iommu.c:1452: d1:PCI: map 0000:00:02.0
>> (XEN) Cannot identity map d1:ad000, already mapped to 115d51.
>> (XEN) [VT-D]iommu.c:2296: IOMMU: mapping reserved region failed
>> (XEN) XEN_DOMCTL_assign_device: assign 0000:00:02.0 to dom1 failed (-1)
>> (XEN) [VT-D]iommu.c:1589: d1:PCI: unmap 0000:00:02.0
>> (XEN) [VT-D]iommu.c:1452: d0:PCI: map 0000:00:02.0
>> ...
>
> So after all device assignment fails in that case, which is what I was
> expecting to happen. Which gets me back to the question: What's
> the value of the two patches for you if with them you can't pass
> through anymore the device you want passed through for the actual
> work you're doing?
>

I don't understand what you mean again. This is true we already known 
previously because this is just a part of the whole solution, right? So 
I can't understand why we can't apply them now unless you're saying 
they're wrong.

When we want to implement a bigger or complicated feature, I think its 
reasonable to phase that with multiple steps.

Thanks
Tiejun