From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91A55C4321E for ; Fri, 2 Dec 2022 16:27:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234151AbiLBQ1s (ORCPT ); Fri, 2 Dec 2022 11:27:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234094AbiLBQ13 (ORCPT ); Fri, 2 Dec 2022 11:27:29 -0500 Received: from wp530.webpack.hosteurope.de (wp530.webpack.hosteurope.de [80.237.130.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5CECA5F5A for ; Fri, 2 Dec 2022 08:27:28 -0800 (PST) Received: from [2a02:8108:963f:de38:eca4:7d19:f9a2:22c5]; authenticated by wp530.webpack.hosteurope.de running ExIM with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) id 1p18sn-0004Gn-3W; Fri, 02 Dec 2022 17:27:25 +0100 Message-ID: <395ad6ef-eb54-ec7e-e131-714f23c84d7a@leemhuis.info> Date: Fri, 2 Dec 2022 17:27:24 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()" Content-Language: en-US, de-DE To: Greg KH Cc: Will Deacon , Amit Pundir , Catalin Marinas , Sibi Sankar , Manivannan Sadhasivam , Robin Murphy , andersson@kernel.org, sumit.semwal@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hch@lst.de References: <20221118123349.GC3697@willie-the-truck> <20221121064224.GB11945@thinkpad> <018517b8-0ae0-54f5-f342-dcf1b3330a13@quicinc.com> <6d637906-e1d5-c481-a73d-2b2b845e223b@leemhuis.info> <20221202100357.GB29396@willie-the-truck> <92a148a3-a8ac-4065-123c-99b72ac3ebeb@leemhuis.info> From: Thorsten Leemhuis In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-bounce-key: webpack.hosteurope.de;regressions@leemhuis.info;1669998448;e46431d0; X-HE-SMSGID: 1p18sn-0004Gn-3W Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02.12.22 17:10, Greg KH wrote: > On Fri, Dec 02, 2022 at 11:34:30AM +0100, Thorsten Leemhuis wrote: >> On 02.12.22 11:03, Will Deacon wrote: >>> On Fri, Dec 02, 2022 at 09:54:05AM +0100, Thorsten Leemhuis wrote: >>>> On 02.12.22 09:26, Amit Pundir wrote: >>>>> On Thu, 1 Dec 2022 at 23:15, Catalin Marinas wrote: >>>>>> >>>>>> On Thu, Dec 01, 2022 at 10:29:39AM +0100, Thorsten Leemhuis wrote: >>>>>>> Has any progress been made to fix this regression? It afaics is not a >>>>>>> release critical issue, but well, it still would be nice to get this >>>>>>> fixed before 6.1 is released. >>>>>> >>>>>> The only (nearly) risk-free "fix" for 6.1 would be to revert the commit >>>>>> that exposed the driver bug. It doesn't fix the actual bug, it only >>>>>> makes it less likely to happen. >>>>>> >>>>>> I like the original commit removing the cache invalidation as it shows >>>>>> drivers not behaving properly >>>> >>>> Yeah, I understand that, but I guess it's my job to ask at this point: >>>> "is continuing to live with the old behavior for one or two more cycles" >>>> that much of a problem"? >>> >>> That wouldn't be a problem. The problem is that I haven't see any efforts >>> from the Qualcomm side to actually fix the drivers [...] >> >> Thx for sharing the details. I can fully understand your pain. But well, >> in the end it looks to me like this commit it intentionally breaking >> something that used to work -- which to my understanding of the "no >> regression rule" is not okay, even if things only worked by chance and >> not flawless. > > "no regressions" for userspace code, this is broken, out-of-tree driver > code, right? If so: apologies. But that's not the impression I got, as Amit wrote "I can reproduce this crash on vanilla v6.1-rc1 as well with no out-of-tree drivers." here: https://lore.kernel.org/linux-arm-kernel/CAMi1Hd3H2k1J8hJ6e-Miy5+nVDNzv6qQ3nN-9929B0GbHJkXEg@mail.gmail.com/ > I do not think any in-kernel drivers have this issue today > from what I can tell, but if I am wrong here, please let me know. > > We don't keep stable apis, or even functionality, for out-of-tree kernel > code as that would be impossible for us to do for obvious reasons. Ciao, Thorsten