Re: [PATCH v9 6/7] iommu/arm-smmu-v3: Add arm_smmu_invs based arm_smmu_domain_inv_range()

Nicolin Chen
2026-01-27T16:39:01Z

Hi Pranjal,

Sorry, I missed this!

On Fri, Jan 23, 2026 at 09:48:37AM +0000, Pranjal Shrivastava wrote:
> On Fri, Dec 19, 2025 at 12:11:28PM -0800, Nicolin Chen wrote:
> > + /*
> > + * Avoid locking unless ATS is being used. No ATC invalidation can be
> > + * going on after a domain is detached.
> > + */
> > + if (invs->has_ats) {
> > + read_lock(&invs->rwlock);
>
> Shouldn't these be read_lock_irqsave for all rwlock variants here?
> Invalidations might happen in IRQ context as well..
>
> > + __arm_smmu_domain_inv_range(invs, iova, size, granule, leaf);
> > + read_unlock(&invs->rwlock);

It was kept from the older versions where we had a trylock. Jason
had an insight about this, mainly for less latency on invalidation
threads.

Yet, now we have a plain locking. TBH, I can't find a good reason
justifying this. And it does look a bit unsafe to me. So, I think
I will just change to the _irqsave version. (Jason?)

Thanks
Nicolin