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 EC1B4C636D4 for ; Mon, 13 Feb 2023 18:33:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229648AbjBMSdB (ORCPT ); Mon, 13 Feb 2023 13:33:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229509AbjBMSdA (ORCPT ); Mon, 13 Feb 2023 13:33:00 -0500 Received: from mail-pj1-f43.google.com (mail-pj1-f43.google.com [209.85.216.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E62B013DE1; Mon, 13 Feb 2023 10:32:58 -0800 (PST) Received: by mail-pj1-f43.google.com with SMTP id oa11-20020a17090b1bcb00b002341a2656e5so1581344pjb.1; Mon, 13 Feb 2023 10:32:58 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=FNk3UELDGb/VaGugwXVxHzDA5RNRGF2dh5FGqDHZODo=; b=TTFnzO1dJz85kCeHttfYg/BxqDzpw1FA3a05wiVvlj6tP3hQhPtAPBxfAfeyjVKWlY MpXgJt2deNy7HFhwEpc21IjjeFrL6LCgacGYloriA4ESSvIF7sxiPdJxEwqPi/vVFSD6 iPIVcca/Fr4gNWHB67Pm3ZYk28TSC71SXWhzvqHGNI+lBSeZISsyepoisjUd09yr/UKk RtURFpdMey+UO85tr+3mp3BpUiXWN9OOrWSjj/gbEwZvf4/eEMOoTSBewUt2xfRasGg2 99nXlf3Dnfc9FMTYrnZhg6Ivuj6CHrQuRm4k98XFIdOxe5ilmVhSKJeLJcN7YiDzt08H 34Yg== X-Gm-Message-State: AO0yUKWI4nfBidMSSnPJz3qFlq4qGCMVRkzmm9MLfFVJRY0BvDaZegV/ nXJ74aA47kRal8IK2qs/aXg= X-Google-Smtp-Source: AK7set8bqfAEsgoBzYy8J6ejBneEGYS/nL6hiIntMGR8g21NqX+cFWzSDRIL7ZHXcO32eieVSJk5Sg== X-Received: by 2002:a17:902:c942:b0:19a:aea3:8a92 with SMTP id i2-20020a170902c94200b0019aaea38a92mr1709128pla.16.1676313178378; Mon, 13 Feb 2023 10:32:58 -0800 (PST) Received: from localhost (fpd11144dd.ap.nuro.jp. [209.17.68.221]) by smtp.gmail.com with ESMTPSA id h13-20020a170902f7cd00b0019a87514e00sm4527517plw.177.2023.02.13.10.32.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Feb 2023 10:32:57 -0800 (PST) Date: Tue, 14 Feb 2023 03:32:54 +0900 From: Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= To: Manivannan Sadhasivam Cc: linux-pci@vger.kernel.org, kishon@kernel.org, lpieralisi@kernel.org, bhelgaas@google.com, linux-kernel@vger.kernel.org, robh@kernel.org, vidyas@nvidia.com, vigneshr@ti.com Subject: Re: [PATCH v5 0/5] PCI: endpoint: Rework the EPC to EPF notification Message-ID: References: <20230124071158.5503-1-manivannan.sadhasivam@linaro.org> <20230124071602.GB4947@thinkpad> <20230213065718.GA4375@thinkpad> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230213065718.GA4375@thinkpad> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hello, > > > During the review of the patch that fixes DBI access in PCI EP, Rob > > > suggested [1] using a fixed interface for passing the events from EPC to > > > EPF instead of the in-kernel notifiers. > > > > > > This series introduces a simple callback based mechanism for passing the > > > events from EPC to EPF. This interface is chosen for satisfying the below > > > requirements: > > > > > > 1. The notification has to reach the EPF drivers without any additional > > > latency. > > > 2. The context of the caller (EPC) needs to be preserved while passing the > > > notifications. > > > > > > With the existing notifier mechanism, the 1st case can be satisfied since > > > notifiers aren't adding any huge overhead. But the 2nd case is clearly not > > > satisfied, because the current atomic notifiers forces the EPF > > > notification context to be atomic even though the caller (EPC) may not be > > > in atomic context. In the notification function, the EPF drivers are > > > required to call several EPC APIs that might sleep and this triggers a > > > sleeping in atomic bug during runtime. > > > > > > The above issue could be fixed by using a blocking notifier instead of > > > atomic, but that proposal was not accepted either [2]. > > > > > > So instead of working around the issues within the notifiers, let's get rid > > > of it and use the callback mechanism. > > > > > > NOTE: DRA7xx and TEGRA194 drivers are only compile tested. Testing this series > > > on the real platforms is greatly appreciated. > > > > > > > Lorenzo, all patches in this series got review tags. Can you please merge now? > > > > Krzysztof, any update on this series? Sorry for the late reply. I just realised that my question from a few days ago has yet to make it to the mailing list. Again, I apologise for keeping you waiting. Nevertheless, I was asking whether there would be any "Fixes:" tags to add and if we should let the stable maintainers know since this fixes an issue that might be worth back-porting to older kernels. Let me know. Otherwise, everything looks good! Thank you a lot! Krzysztof