Re: [PATCH] intel-iommu: Default to non-coherent for domainsunattached to iommus

[Chris Wright]

* cody (mail.kai.huang@xxxxxxxxx) wrote:
> On 11/11/2011 05:20 PM, David Woodhouse wrote:
> >On Fri, 2011-11-11 at 17:08 -0800, Chris Wright wrote:
> >>On a slightly separate, but performance related note...have you ever
> >>tried using the hw queue?  Currently we only have a sw queue, but the
> >>submission path for invalidations doesn't really queue (unless I missed
> >>it).  It seems to pull from the software queue and submit/wait,
> >>submit/wait...Seems simple enough to submit the whole queue and then
> >>issue the wait.
> >I have a feeling we trigger errata if we do that â although if we're
> >only doing it for an emulated IOMMU that shouldn't be an issue.
> >
> What does the emulated IOMMU here? Does it mean the emulated IOMMU
> exposed to guest VM?

Yes.  So for KVM, the IOMMU emulation would be in QEMU.

thanks,
-chris
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