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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.09.14 at 11:05, <tiejun.chen@xxxxxxxxx> wrote:
> On 2014/9/22 16:53, Jan Beulich wrote:
>>>>> On 22.09.14 at 07:46, <tiejun.chen@xxxxxxxxx> 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.

You want these two patches applied despite having acknowledged
that even for you they cause a regression (at the very least an
apparent one).

Jan


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