On Fri, Mar 06, 2026 at 03:22:11PM -0400, Jason Gunthorpe wrote:

On Fri, Mar 06, 2026 at 11:20:35AM -0800, Nicolin Chen wrote:

quoted

In general, the maximum users count of an INV_TYPE_ATS would be 1.
So, an unref() would be sufficient to mute it, though it'd require
the unref() API to support a mismatched users counter, because the
PCI reset in the WQ would block ATS, which would try to unref the
removed command once again.

INV_TYPE_ATS_DISABLED could be made to work too..

Overriding the type.. hmm, that's brilliant.

Rechecking the unref API, I realized that even the "users" in the
latest version isn't atomic anymore. I recall that we are fine to
do READ_ONCE/WRITE_ONCE on an int type because invalidation array
is serialized by the asid mutex, which wouldn't work either in an
ISR or just in the arm_smmu_master/domain_atc_inv()?

Thanks
Nicolin