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

[Yu Zhang]

On Mon, Aug 17, 2026 at 09:22:16AM -0300, Jason Gunthorpe wrote:
> 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.
> 

Got it. Will drop the check and make sure each blocking request
reasserts the blocking state in Hyper-V at HW level.

B.R.
Yu

> Jason
>