Re: [Xen-devel] [PATCH] iommu: leave IOMMU enabled by default during kexec crash transition

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

On 20/02/2019 09:01, Jan Beulich wrote:
> But isn't it a valid question whether keeping interrupt remapping
> enabled is helpful or potentially making things worse? The
> description of the patch discusses the DMA translation aspects
> only. Unless the crash kernel would always operate in polling
> mode only, it needs to have interrupts routed to the right
> handler(s). Whether that's guaranteed with remapping left
> enabled is not something that goes without saying, imo.
> 

IR copy logic works as follows - IRT is copied as is and still in
functioning state while remapable interrupts might be in-flight. New IRT
entries are allocated in addition to existing ones which makes the
transition transparent for a device. I'll mention this aspect in the
commit message since it doesn't seem obvious - you're right.

Igor

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