Re: [PATCH v1 2/2] iommu/arm-smmu-v3: Recover ATC invalidate timeouts

Nicolin Chen
2026-03-06T05:06:51Z

On Thu, Mar 05, 2026 at 09:33:47PM -0400, Jason Gunthorpe wrote:
> On Thu, Mar 05, 2026 at 05:29:22PM -0800, Nicolin Chen wrote:
>
> > But arm_smmu_cmdq_issue_cmdlist() doesn't know when to push another
> > CMD. In my case where ATC_INV irq occurs, the return value from the
> > arm_smmu_cmdq_poll_until_sync() in the Step 5 is 0, and prods/cons
> > are also matched. Actually, at this point that NOP ISR has already
> > finished.
>
> Yes, you'd need a sneaky way to convay the error from the ISR to the
> cmdlist code that didn't harm performance. Maybe we could come up with
> something, but if it works replacing the NOP with flush sounds fairly
> appealing - though can you do a single WORD edit to the STE that will
> block translated requests? Zero EATS?

Yea. I can give that a try.

> Also, will the SMMU start spamming with blocked translation events or
> something that will need suppression too?

CD.R=0 can suppress fault records, but we would need to override
that in every CD of the device.

Thanks
Nicolin