Re: [Xen-devel] VT-d flush timeout

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, September 25, 2014 4:48 AM
> 
> >>> On 25.09.14 at 12:56, <andrew.cooper3@xxxxxxxxxx> wrote:
> > On 25/09/14 11:55, Jan Beulich wrote:
> >>>>> On 25.09.14 at 12:44, <andrew.cooper3@xxxxxxxxxx> wrote:
> >>> The AMD code will wait for a period of time for the COMMAND_WAIT to
> >>> start, but not panic() on a timeout.
> >>>
> >>> By my reading of the code, amd_iommu_flush_iotlb() can complete
> without
> >>> confirming that the iotlbs have actually been flushed, and all that is
> >>> left behind is an AMD_IOMMU_DEBUG() message.
> >> Now that you say this I recall having stumbled across this questionable
> >> behavior in the past (and perhaps even more than once). Certainly
> >> something for our AMD IOMMU maintainers to look into...
> >
> > Agreed, although for now I think it is safer to leave ATS disabled.
> 
> Fully agree.
> 

I agree with this, until we have the asynchronous wait scheme implemented.
And we don't need to change the timeout value for non-ATS cases, as discussed
earlier.

Thanks
Kevin

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