Re: [Xen-devel] [PATCH v12 1/6] IOMMU: add a timeout parameter for device IOTLB invalidation

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

> From: Xu, Quan
> Sent: Friday, June 24, 2016 1:52 PM
> 
> From: Quan Xu <quan.xu@xxxxxxxxx>
> 
> The parameter 'iommu_dev_iotlb_timeout' specifies the timeout
> of device IOTLB invalidation in milliseconds. By default, the
> timeout is 1000 milliseconds, which can be boot-time changed.
> 
> We also confirmed with VT-d hardware team that 1 milliseconds
> is large enough for VT-d IOMMU internal invalidation.
> 
> the existing panic() is eliminated and we bubble up the timeout
> of device IOTLB invalidation for further processing, as the
> PCI-e Address Translation Services (ATS) mandates a timeout of
> 60 seconds for device IOTLB invalidation. Obviously we can't
> spin for 60 seconds or otherwise Xen hypervisor hangs.
> 
> Add a __must_check annotation. The followup patch titled
> 'VT-d IOTLB/Context/IEC flush issue' addresses the __mustcheck.
> That is the other callers of this routine (two or three levels up)
> ignore the return code. This patch does not address this but the
> other does.
> 
> Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
> 

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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