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Tue, 31 Mar 2020 07:53:34 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id DB692C433D2; Tue, 31 Mar 2020 07:53:33 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id 31674C433F2; Tue, 31 Mar 2020 07:53:33 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 31 Mar 2020 13:23:33 +0530 From: Sai Prakash Ranjan To: Will Deacon Subject: Re: [PATCH] iommu/arm-smmu: Demote error messages to debug in shutdown callback In-Reply-To: <20200331074400.GB25612@willie-the-truck> References: <20200327132852.10352-1-saiprakash.ranjan@codeaurora.org> <0023bc68-45fb-4e80-00c8-01fd0369243f@arm.com> <37db9a4d524aa4d7529ae47a8065c9e0@codeaurora.org> <5858bdac-b7f9-ac26-0c0d-c9653cef841d@arm.com> <890456524e2df548ba5d44752513a62c@codeaurora.org> <20200331074400.GB25612@willie-the-truck> Message-ID: <1bf04938249bcd5b2111c1921facfd25@codeaurora.org> X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Cc: linux-arm-msm , Doug Anderson , LKML , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Robin Murphy X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" 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 >> > 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 -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu