Re: [Xen-devel] [PATCH] libxl: disallow PCI device assignment for HVM guest when PoD is enabled

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.01.14 at 15:03, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> On Fri, Jan 10, 2014 at 12:28:52PM +0000, Jan Beulich wrote:
>> >>> On 10.01.14 at 13:16, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>> > On 10/01/2014 11:46, Wei Liu wrote:
>> >> On Fri, Jan 10, 2014 at 11:39:51AM +0000, Jan Beulich wrote:
>> >>>>>> On 10.01.14 at 12:27, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
>> >>>> +    /* We cannot have PoD and PCI device assignment at the same time
>> >>>> +     * for HVM guest. It was reported that VT-d engine cannot
>> >>> There's still a "VT-d" left in here...
>> >>>
>> >> I mentioned AMD as well. Was trying to clarify things a bit more...
>> > 
>> > Use "IOMMU"/"PCI Passthrough"/etc as appropriate, which are vendor neutral.
>> > 
>> > There is no way for for PoD (or Paging for that matter) to work in
>> > combination with PCIPassthrough, as you need all the backing RAM for all
>> > gfns to exist to receive DMA.
>> 
>> That's going a little too far: If IOMMU faults were recoverable, dealing
>> with non-present pages would become possible (with other caveats
>> of course). So this is not a fundamental attribute of IOMMUs, but
>> there doesn't seem to be any reason to believe that the current
>> model would change any time soon for either of the vendors.
>> 
> 
> Do you have suggestion on how this comment should be phrased?

Just say "IOMMU" or "DMA remapping" instead of "VT-d".

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel