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 425EDC433EF for ; Sat, 26 Mar 2022 22:42:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235138AbiCZWnm (ORCPT ); Sat, 26 Mar 2022 18:43:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235081AbiCZWnk (ORCPT ); Sat, 26 Mar 2022 18:43:40 -0400 Received: from mail-lj1-x234.google.com (mail-lj1-x234.google.com [IPv6:2a00:1450:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B71082F3B4 for ; Sat, 26 Mar 2022 15:42:03 -0700 (PDT) Received: by mail-lj1-x234.google.com with SMTP id a30so7142009ljq.13 for ; Sat, 26 Mar 2022 15:42:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=lSLy1cPxoDC//3e7623ZX4es74MP3w4cCLgF29j5fUU=; b=HTqOpqutn/t7/GJQrakk/gAhabnVwnukxwMtMja/1SljWHCaJh+ZhMav3V4OqLq1/m JldSGIs54yIcMbIeQmTLdzLUuMQeARuWCJqZUzEEphC4IEXZ9NChSkH88YY0FSWwPQJu U24K7ZOq8FQZ2yFFgeY8MWj+ZVkdrqhAUb3Tw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lSLy1cPxoDC//3e7623ZX4es74MP3w4cCLgF29j5fUU=; b=d/cNVQU37c10B/QUW6B5AptCBPypqMpW64g4ujY2EOP4j2hdlFA4xMmP7sFcrv2z99 CLs/MbhlSJRruvsa6vxUnm58IXucaSR5nq7Jjz71fuseg2gZ3fIjwIuSRkUX1KQkHUb7 TpPz0nmmtxMn0vIinIpLwVF0o0EC4qXdIolW2xBmD8eb3Bj0EIvlOAmB36BG/YJYWuek cuVMd8mxNFmKq0mA2h59+Mx1pQkGJuhxDiFcyJHPWfwHNRwG+KXSgxayN4xRKMyHJ26e dEEEGghUajCA5EmH20PtqhCwSDHZLf2bvxqKr466k7pnufghqO4DTtGgI2+JGk8xU/dK sVLw== X-Gm-Message-State: AOAM531V22TT44i4DNE0Nlft8XYQtVWJ5G+Fig6EMBBlLXWwyepEuBSx qQWxqjA3Geb6tCkQd57tB+GoyghxXGUSaF0vbII= X-Google-Smtp-Source: ABdhPJz4V+ddpTwNxhWNtTRr/5B6dslV/YXa1AVnsQLeXbA7IcGWC2vYjU9r/GZhKX5l0w7L/2/Z7g== X-Received: by 2002:a2e:bc19:0:b0:249:b29c:7f5e with SMTP id b25-20020a2ebc19000000b00249b29c7f5emr10709945ljf.312.1648334521771; Sat, 26 Mar 2022 15:42:01 -0700 (PDT) Received: from mail-lf1-f47.google.com (mail-lf1-f47.google.com. [209.85.167.47]) by smtp.gmail.com with ESMTPSA id q21-20020a194315000000b0044a1e36fda4sm1190366lfa.25.2022.03.26.15.41.57 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 26 Mar 2022 15:41:59 -0700 (PDT) Received: by mail-lf1-f47.google.com with SMTP id bq24so3056401lfb.5 for ; Sat, 26 Mar 2022 15:41:57 -0700 (PDT) X-Received: by 2002:a05:6512:b13:b0:448:90c6:dc49 with SMTP id w19-20020a0565120b1300b0044890c6dc49mr13805287lfu.542.1648334517200; Sat, 26 Mar 2022 15:41:57 -0700 (PDT) MIME-Version: 1.0 References: <1812355.tdWV9SEqCh@natalenko.name> <20220324055732.GB12078@lst.de> <4386660.LvFx2qVVIh@natalenko.name> <81ffc753-72aa-6327-b87b-3f11915f2549@arm.com> <878rsza0ih.fsf@toke.dk> <4be26f5d8725cdb016c6fdd9d05cfeb69cdd9e09.camel@freebox.fr> <20220324163132.GB26098@lst.de> <871qyr9t4e.fsf@toke.dk> <31434708dcad126a8334c99ee056dcce93e507f1.camel@freebox.fr> <20220326003853.44c3285c.pasic@linux.ibm.com> <8735j47l7y.fsf@toke.dk> In-Reply-To: From: Linus Torvalds Date: Sat, 26 Mar 2022 15:41:40 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break ath9k-based AP To: David Laight Cc: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Halil Pasic , Robin Murphy , Maxime Bizon , Netdev , Kalle Valo , linux-wireless , Oleksandr Natalenko , stable , "David S. Miller" , iommu , Olha Cherevyk , Greg Kroah-Hartman , Jakub Kicinski , Paolo Abeni , Christoph Hellwig , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Mar 26, 2022 at 3:38 PM David Laight wrote: > > Is the idea of 'buffer ownership' even a good one? I do think it might be best to not think in those terms, but literally just in data movement terms. Because the "buffer ownership" mental model is clearly confused, when data transfer might be ongoing, but the CPU might need to just look at "what's going on right now" without actually taking any ownership of the buffer. Linus