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

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:

quoted

quoted

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