Messages in this thread | | | Date | Tue, 31 Mar 2020 13:23:33 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH] iommu/arm-smmu: Demote error messages to debug in shutdown callback |
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Hi Will,
On 2020-03-31 13:14, Will Deacon wrote: > On Tue, Mar 31, 2020 at 01:06:11PM +0530, Sai Prakash Ranjan wrote: >> On 2020-03-30 23:54, Doug Anderson wrote: >> > On Sat, Mar 28, 2020 at 12:35 AM Sai Prakash Ranjan >> > <saiprakash.ranjan@codeaurora.org> wrote: >> > > >> > > > Of course the fact that in practice we'll *always* see the warning >> > > > because there's no way to tear down the default DMA domains, and even >> > > > if all devices *have* been nicely quiesced there's no way to tell, is >> > > > certainly less than ideal. Like I say, it's not entirely clear-cut >> > > > either way... >> > > > >> > > >> > > Thanks for these examples, good to know these scenarios in case we >> > > come >> > > across these. >> > > However, if we see these error/warning messages appear everytime then >> > > what will be >> > > the credibility of these messages? We will just ignore these messages >> > > when >> > > these issues you mention actually appears because we see them >> > > everytime >> > > on >> > > reboot or shutdown. >> > >> > I would agree that if these messages are expected to be seen every >> > time, there's no way to fix them, and they're not indicative of any >> > problem then something should be done. Seeing something printed at >> > "dev_error" level with an exclamation point (!) at the end makes me >> > feel like this is something that needs immediate action on my part. >> > >> > If we really can't do better but feel that the messages need to be >> > there, at least make them dev_info and less scary like: >> > >> > arm-smmu 15000000.iommu: turning off; DMA should be quiesced before >> > now >> > >> > ...that would still give you a hint in the logs that if you saw a DMA >> > transaction after the message that it was a bug but also wouldn't >> > sound scary to someone who wasn't seeing any other problems. >> > >> >> We can do this if Robin is OK? > > It would be nice if you could figure out which domains are still live > when > the SMMU is being shut down in your case and verify that it *is* infact > benign before we start making the message more friendly. As Robin said > earlier, rogue DMA is a real nightmare to debug. >
I could see this error message for all the clients of apps_smmu. I checked manually enabling bypass and removing iommus dt property for each client of apps_smmu.
Thanks, Sai
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