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 B739AC4321E for ; Fri, 2 Dec 2022 16:33:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233568AbiLBQdH (ORCPT ); Fri, 2 Dec 2022 11:33:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234071AbiLBQc4 (ORCPT ); Fri, 2 Dec 2022 11:32:56 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A7674508C for ; Fri, 2 Dec 2022 08:32:55 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 166246233A for ; Fri, 2 Dec 2022 16:32:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF39AC433D6; Fri, 2 Dec 2022 16:32:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669998774; bh=pQ7g0nDMOMcY6daJmycAqY67TFIHNGmsVxECzKIRMaE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1s3wulxVdXIVq63bb87WUMUUL+XldGTyL7zWeuy5CHBc6+Xspp0QWBY2C5xcWatCl 88nRgRjSA9XlLB0ROROfY4ObT2oVdXFa2PfqLdv2SaUZj7ufAVg7d0eiVPBw9d7gB9 45ZkQaeX5l/ZydAUSGRq8i0AvssFWLnFfapK05P4= Date: Fri, 2 Dec 2022 17:32:51 +0100 From: Greg KH To: Thorsten Leemhuis 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 Subject: Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()" Message-ID: References: <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> <395ad6ef-eb54-ec7e-e131-714f23c84d7a@leemhuis.info> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <395ad6ef-eb54-ec7e-e131-714f23c84d7a@leemhuis.info> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2022 at 05:27:24PM +0100, Thorsten Leemhuis wrote: > > > 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/ Ah, I missed that. Ok, what in-tree drivers are having problems being buggy? I can't seem to figure that out from that report at all. Does anyone know? thanks, greg k-h