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Re: [Xen-devel] swiotlb and Xen query?

  • To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • From: "pradeep singh rautela" <rautelap@xxxxxxxxx>
  • Date: Thu, 3 May 2007 14:54:55 +0530
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 03 May 2007 02:23:26 -0700
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On 5/3/07, Petersson, Mats <Mats.Petersson@xxxxxxx> wrote:
> That was really very informative Mats.
> Thanks you very much for the help.
> So, i guess swiotlb comes into picture only if there is a DMA
> transfer from a domU whose p2m mapping turns out to be above
> the 4GB( assuming device to be 32 bit) of the machine memory.
> Other wise just normal p2m mapping is enough to find the
> actual machine address, which can be handed over to the
> device for DMAing. Am i right?

Yes, that's pretty much how it works. In theory, it could be that
devices only work on a 31, 28 or some other number of bit-range, but
yes, that's the principle.

Ok.Got this correct.
I am sure this can cause problems while migrating live domains across cpus.

Thank you

> Thank you once again for the patience.
> Regards
> ~psr

pradeep singh rautela

"Genius is 1% inspiration, and 99% perspiration" - not me :)
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