[Bug 201753] AMD-Vi: Unable to write to IOMMU perf counter

bugzilla-daemon
2021-03-08T10:47:07Z

--- Comment #21 from David Coe (david.coe@live.co.uk) ---
Good morning, Suravee!

One (final?!) test of your patch (with increased retry count and logging) on
the latest git kernel (5.10.0-rc2) all on Ryzen 2400G. In summary:

5.8.0-44 (Ubuntu 20.10) 6 trys 20 msecs
5.10.0-14 (Ubuntu 21.04) 5 trys 20 msecs
5.12.0-rc2 (raw git) 6 trys 20 msecs

AFAIK you are AMD's go-to guru for open-source people and an IOMMU expert. It's
your patch that is now both in the kernel commit and (I hope) in Ubuntu's to-do
list. Could I ask if you could patch-the-patch (if there is no esoteric
technical downside) to increase the number of retrys? Maybe if Paul would give
it another shot with his Ryzen 2200G with a larger maximum count and his
logging :-).

Best regards and our thanks

David