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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A9AFC433DF for ; Tue, 30 Jun 2020 10:55:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EA012073E for ; Tue, 30 Jun 2020 10:55:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593514541; bh=xpXgFc6VJxI7yVbdK+oqDekGciZztfNlNY9vpGzixVE=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=IE8W4YqenG80/bncXrKt+uKBPmXVjg2EugGRMQzKlyzIy9QpDnygHxyHwN+KnJ3ui sm5JAeW9Eq+FHzTr+iWu+trTgLBJuZx1C2Os2rrBy0O8JNRwb2nuUGshiGF82d/VaD 5fSF2KE8wA8z5nsQCYtuRKI1GDgokxWU44XsehJE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732713AbgF3Kzk (ORCPT ); Tue, 30 Jun 2020 06:55:40 -0400 Received: from mail-oi1-f196.google.com ([209.85.167.196]:33728 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732697AbgF3Kzj (ORCPT ); Tue, 30 Jun 2020 06:55:39 -0400 Received: by mail-oi1-f196.google.com with SMTP id k22so5710124oib.0; Tue, 30 Jun 2020 03:55:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hTbwPpfXI9xMDRsJXGGIpIBFM8wdp1+JDn7sklMEIMA=; b=bMOQLUrrAjciG+YqTsVKynDdJEn+RLJ6NkWRn6vP/k/zSwLmRL3ICIfbYZZ6r0ZO3J 3+fRfm4+o9coIi1u5/z3OdMBHdkJQvnB9tyHfr29nIaAvY7lHxoOjr5wmuQwoRz+566u Kk6MrNnIg0K365z77V54ox6cvIWShAmmVKeELW9OLgwtE2d9bGog4k4F87n3NHktkNxA SaEptQghwTkTR+eJMvRuG+wXNpTAqs4U5vQksLmJ0l8uIaBzJ563ey1x41ATBzGwDrI6 QCG81h9gCTcCz+yv2HLwH8trcMWWP5mVHkw4X75uJqrc7qz7agI1Ff1FyYtxsjSpLS7v pCHA== X-Gm-Message-State: AOAM531xusrdkSauo/j7kKR8p37I4BtdSAFialE3rICBL4CIRbE9sK9r i7gSRoxtkv1zX0CUo7Fh3xSDFhzKQXiINDiYUSA= X-Google-Smtp-Source: ABdhPJyq1ZXnEfTbtsudUdaXDZrpsPo5g98IZqG6sv/5uEyV5HYApUjKZQyJd4BIkIqWp1JEVXC7zVOCno7knl/SaNo= X-Received: by 2002:aca:f58a:: with SMTP id t132mr9637240oih.68.1593514536147; Tue, 30 Jun 2020 03:55:36 -0700 (PDT) MIME-Version: 1.0 References: <159312902033.1850128.1712559453279208264.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: From: "Rafael J. Wysocki" Date: Tue, 30 Jun 2020 12:55:24 +0200 Message-ID: Subject: Re: [PATCH 00/12] ACPI/NVDIMM: Runtime Firmware Activation To: Dan Williams Cc: "Rafael J. Wysocki" , "linux-nvdimm@lists.01.org" , Ira Weiny , Dave Jiang , "Rafael J. Wysocki" , Vishal Verma , Andy Shevchenko , Jonathan Corbet , Greg Kroah-Hartman , Len Brown , Len Brown , "Rafael J. Wysocki" , Pavel Machek , Stable , ACPI Devel Maling List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Jun 30, 2020 at 1:37 AM Dan Williams wrote: > > On Sun, Jun 28, 2020 at 10:23 AM Rafael J. Wysocki wrote: > > > > On Fri, Jun 26, 2020 at 8:43 PM Dan Williams wrote: > > > > > > On Fri, Jun 26, 2020 at 7:22 AM Rafael J. Wysocki wrote: > > > > > > > > On Fri, Jun 26, 2020 at 2:06 AM Dan Williams wrote: > > > > > > > > > > Quoting the documentation: > > > > > > > > > > Some persistent memory devices run a firmware locally on the device / > > > > > "DIMM" to perform tasks like media management, capacity provisioning, > > > > > and health monitoring. The process of updating that firmware typically > > > > > involves a reboot because it has implications for in-flight memory > > > > > transactions. However, reboots are disruptive and at least the Intel > > > > > persistent memory platform implementation, described by the Intel ACPI > > > > > DSM specification [1], has added support for activating firmware at > > > > > runtime. > > > > > > > > > > [1]: https://docs.pmem.io/persistent-memory/ > > > > > > > > > > The approach taken is to abstract the Intel platform specific mechanism > > > > > behind a libnvdimm-generic sysfs interface. The interface could support > > > > > runtime-firmware-activation on another architecture without need to > > > > > change userspace tooling. > > > > > > > > > > The ACPI NFIT implementation involves a set of device-specific-methods > > > > > (DSMs) to 'arm' individual devices for activation and bus-level > > > > > 'trigger' method to execute the activation. Informational / enumeration > > > > > methods are also provided at the bus and device level. > > > > > > > > > > One complicating aspect of the memory device firmware activation is that > > > > > the memory controller may need to be quiesced, no memory cycles, during > > > > > the activation. While the platform has mechanisms to support holding off > > > > > in-flight DMA during the activation, the device response to that delay > > > > > is potentially undefined. The platform may reject a runtime firmware > > > > > update if, for example a PCI-E device does not support its completion > > > > > timeout value being increased to meet the activation time. Outside of > > > > > device timeouts the quiesce period may also violate application > > > > > timeouts. > > > > > > > > > > Given the above device and application timeout considerations the > > > > > implementation defaults to hooking into the suspend path to trigger the > > > > > activation, i.e. that a suspend-resume cycle (at least up to the syscore > > > > > suspend point) is required. > > > > > > > > Well, that doesn't work if the suspend method for the system is set to > > > > suspend-to-idle (for example, via /sys/power/mem_sleep), because the > > > > syscore callbacks are not invoked in that case. > > > > > > > > Also you probably don't need the device power state toggling that > > > > happens during regular suspend/resume (you may not want it even for > > > > some devices). > > > > > > > > The hibernation freeze/thaw may be a better match and there is some > > > > test support in there already that may be kind of co-opted for your > > > > use case. > > > > > > Hmm, yes I guess freeze should be sufficient to quiesce most > > > device-DMA in the general case as applications will stop sending > > > requests. > > > > It is expected to be sufficient to quiesce all of them. > > > > If that is not the case, the integrity of the hibernation image cannot > > be guaranteed on the system in question. > > > > Ah, indeed, I was overlooking that property. > > > > I do expect some RDMA devices will happily keep on > > > transmitting, but that likely will need explicit mitigation. It also > > > appears the suspend callback for at least one RDMA device > > > mlx5_suspend() is rather violent as it appears to fully teardown the > > > device context, not just suspend operations. > > > > > > To be clear, what debug interface were you thinking I could glom onto > > > to just trigger firmware-activate at the end of the freeze phase? > > > > Functionally, the same as for suspend, but using the hibernation > > interface, so "echo platform > /sys/power/pm_test" followed by "echo > > disk > /sys/power/state". > > > > But it might be cleaner to introduce a special "hibernation mode", ie. > > is one more item in /sys/power/disk, that will trigger what you need > > (in analogy with "test_resume"). > > I'll move the trigger to be after process freeze, but I'll keep it > tied to suspend-debug vs hibernate-debug. It appears the hibernate > debug path still goes through the exercise of allocating memory for > the hibernation image which is unnecessary if the goal is just to > 'freeze', 'activate', and 'thaw'. But you need the ->freeze and ->thaw callbacks to run which does not happen at the process freeze stage. If you add a new hibernation mode dedicated to the NVDIMM firmware update, though, you can instrument the code to skip the memory allocation if this mode is selected.