Re: [PATCH v3 4/5] iommu/hyperv: Add para-virtualized IOMMU support for Hyper-V guest

[Jason Gunthorpe]

On Fri, Aug 14, 2026 at 05:37:48PM +0800, Yu Zhang wrote:
> > Why check it at all? Is there an issue with attaching the same thing
> > twice? Will it blip the DMA or something?
> 
> Actually, I do not think there should be any issue with attaching twice.
> Hyper-V *should* be able to accept such attachment. But I do not want to
> make such assumption just for a redundant hypercall.
> 
> Does this reasoning make sense, or would you prefer that I remove the
> check?

I would probably drop it. Having blocking always set blocking to the
HW regardless of what the SW tracking state says feels more robust to
me.

Jason