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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 54AFAC88E4D for ; Fri, 11 Sep 2026 17:00:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4E9856B008A; Fri, 11 Sep 2026 13:00:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4C0D46B008C; Fri, 11 Sep 2026 13:00:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3FE1D6B009E; Fri, 11 Sep 2026 13:00:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 170FC6B008A for ; Fri, 11 Sep 2026 13:00:21 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id A56ADA02F6 for ; Fri, 11 Sep 2026 17:00:20 +0000 (UTC) X-FDA: 85202094600.04.761A432 Received: from mail-oa1-f54.google.com (mail-oa1-f54.google.com [209.85.160.54]) by imf22.hostedemail.com (Postfix) with ESMTP id CDFA2C0009 for ; Fri, 11 Sep 2026 17:00:18 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=HFaDaZnu; spf=pass (imf22.hostedemail.com: domain of dmatlack@google.com designates 209.85.160.54 as permitted sender) smtp.mailfrom=dmatlack@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789146018; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=mwDk3fh+JvGyN78BSU6J48zvCwmsI7FUHYkydOLS1VI=; b=mFBDDbFV5KjqUdFanpt7zdRkEwAWwnYTfAlUTBqH0N9zc96raO6KNqABMzcbMRsNR/uwFK CaJwC0WJHY+Fh4uKgOR8cXaqqr6kEM1IRdYfmLYoSUEHR/y4Kf23/fMU4r1ojWPhvABqtB c/3ZJrFDciUzsxQaexBtQZkmTn59vvE= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=HFaDaZnu; spf=pass (imf22.hostedemail.com: domain of dmatlack@google.com designates 209.85.160.54 as permitted sender) smtp.mailfrom=dmatlack@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789146018; b=IoRStJH8bKaCYBQA43UO6lsxAFfS4Dpbla/wN2R2YEpCj/3PbClJttt6n7ZxL3GOex0NtJ hAJ+Fn4a5KSH+7vJ+UsQ/1TE57DxAuPABFzZS85pve/iNg46MBSe0Hcb0YpecnfcYaKPps UH+ddzVT66buR0usQi8Bl4Olpu9QVdA= Received: by mail-oa1-f54.google.com with SMTP id 586e51a60fabf-43b7e186a0cso597819fac.0 for ; Fri, 11 Sep 2026 10:00:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789146018; x=1789750818; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=mwDk3fh+JvGyN78BSU6J48zvCwmsI7FUHYkydOLS1VI=; b=HFaDaZnuAOXVp17jndDK5xRo4DSVDZGvVeBS+ajV3cAzlzYE0EXFDAuE6crL8yGRRC 9Z4n84ULqIt5OXwEf/Dt2W9A8NVEI+OY21ZnJ9Yzq+gMR7u31pqgBXmbTyMQZ1a0Vvj+ l1qggd0fhQ2RIIpGocJWBn2zqZUc4JXJ0iG4UqCfFBeQCzNVUYFFQLFG89YAnkuKyfm6 c5m8uY9KysKlwXNhMLc/Di5pi9zk/udVXnb3R5fpZ16jASH8sj9n9LEKUwUiERwtqBgE kR+AcVdr3Y/GSaBEPQvQh4bDGeQ/vSXWRQSOfz56kY6mIRC9oX4Rih2toDL53QsRov51 Thhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789146018; x=1789750818; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=mwDk3fh+JvGyN78BSU6J48zvCwmsI7FUHYkydOLS1VI=; b=izK9QnS+g5UwkR6XpqrMW0SXYxIyyFdmWZIXxyNSK96XnOj8OwYMtI09/Xv361w3JN XePn6bjaSWaVdh9WTkMNnsM/4nwRJFNcIPAyd/jany4xmu/ZL5N3sJ/4DzaSFQtfPMUN YNFRF1mo7qvV+OZh9LM1Z/+Q0oNxPbJUrI9tePPe7+9xPwDGmNnNiED/zUp96YXAdofY NlPrETEtFm+ptTyjzpPGQVD/SnJITAudpeqcrt6wbowbfxuaaTfvelYthLGvFjJC2WQA LvzBsTrbtEWzg6a/q9bmKWrKNc77OGDgWHq332bmdQe2ys6fP4rT+0hkPD9AuqMj5OBE 6yfQ== X-Forwarded-Encrypted: i=1; AKwUvBwZ9hVlazlupShVuaqqlUXlAHoVKhE5liWK6XHorRfbfdHfc/PS9PYKpNm+T6rQr/UNLle6PhtHTw==@kvack.org X-Gm-Message-State: AFuF++l+thVtP7jOsuXJhECLiCxBcnFLoCYQADQ1FqByPD2eVdBPF8CH euIxZi9zkYTkaJPHaUDtqq7nUIqEoPyl37a5tB2F6NdiykXmPaOHTd04nC0MK0IA2g== X-Gm-Gg: AYBFou2Tv9QYsOPLwoANwLbD6ksnMFpK2sIINL7X3JYFhA0Ni8zKn9AZTNUDS86VD4q uh+6Qp1tQPAykRo13kqeTVYYtY26ntoRaf2N7YV0Ttr2wVmcZSFosNUfPl+OeHfwprNZYDhLPdt JgJfvp0FC5DnmZrQ/S0zQX9htd3kqGBcwJ9L+0GV7t0EUekjTTuuZ0WTELINyxzheTTp9JvaVrz v0rWCX839JxMeoMRbKUF/TShkLGiYlQdQEBRfTrzsV68cCzRaPaDnBeLLzttY78v0gwFmXZdYEu qFIvnXGPjbDw91pMGo6Al6NYArbAfyyb5rBmqKUfS6NNUscRIoOoCPMSV7a278eIsE1xa5FkeDQ zpE0DY2FBh/xtcjjb/J/y97h7Kevu+LYy2WnVo1vCYSBsPbmEqh97/9L4YyXv+yOvy25gNoykxZ XnttOJ79JE7ow44UTOx99XagoZwl9/5KQqhNgzZKmxm/TGk7jGzmuvqy20WmBadfcZmMjYF2VZ7 FQQVf8+THcgtmQUPmoyZR6ASmZs+EkRfp9Qb6TP X-Received: by 2002:a05:6870:7183:b0:475:a112:1275 with SMTP id 586e51a60fabf-47debded110mr3337322fac.34.1789146016740; Fri, 11 Sep 2026 10:00:16 -0700 (PDT) Received: from google.com (192.150.203.35.bc.googleusercontent.com. [35.203.150.192]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-47df8bd0284sm2467114fac.9.2026.09.11.10.00.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Sep 2026 10:00:14 -0700 (PDT) Date: Fri, 11 Sep 2026 17:00:10 +0000 From: David Matlack To: Bjorn Helgaas Cc: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v8 06/12] PCI: liveupdate: Auto-preserve upstream bridges across Live Update Message-ID: References: <20260728221007.2098560-7-dmatlack@google.com> <20260910235126.GA367952@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260910235126.GA367952@bhelgaas> X-Rspam-User: X-Stat-Signature: pxbumbs84rh1rkomsc6ums8fod53tm8h X-Rspamd-Queue-Id: CDFA2C0009 X-Rspamd-Server: rspam07 X-HE-Tag: 1789146018-661490 X-HE-Meta: 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 SohhItM0 yloWK2RyaWtlbX25FLeXqrHYkAGesrwadjE7eK87TwHREOm/LHl1DN8jdEvtDndp5X2I1a03a5nvmumMUJhUb3/4imYjBA/Ibs2XVUeFX16oi9mYggk3LagfYG+jFMlDMr2utwl28raHw9dQnk5yP4xqBSe9DhqE4eff6F9jd0sDmgKsjad2WNFuUDygT3enGyz8xp6d5atuk85J6c9rl1LONuFVdNl0P7OY9WYKi7ysS9q7YrJ3tw1bCPE2rF/8h8HbCPG9FUjUll1aUYV8a4QkAKFGILbBkDpNLkHzcIFXUNUVuhWuhvFgm90LQ9nzo1/0W76BXc9A/eHDqu3EGitFjm4teJjW3ES5qhb5cZfv/TGU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2026-09-10 06:51 PM, Bjorn Helgaas wrote: > On Tue, Jul 28, 2026 at 10:10:00PM +0000, David Matlack wrote: > > When a PCI device is preserved across a Live Update, all of its upstream > > bridges up to the root port must also be preserved. This enables the PCI > > core and any drivers bound to the bridges to manage bridges correctly > > across a Live Update. > > > > Notably, this will be used in subsequent commits to ensure that > > preserved devices can continue performing memory transactions without a > > disruption or change in routing. > > > > To preserve bridges, the PCI core tracks the number of downstream > > devices preserved under each bridge using a reference count in struct > > pci_dev_ser. This allows a bridge to remain preserved until all its > > downstream preserved devices are unpreserved or finish their > > participation in the Live Update. > > This seems to hint that we're going to allow bridge reconfiguration in > some cases, e.g., for hot-adds. The simplest case is "leave config of > all bridges the same", and I thought that was what the previous patch > commit log said. > > What's the benefit added by this patch? It is used in the following patches: PCI: liveupdate: Adopt ACS controls in incoming preserved devices PCI: liveupdate: Adopt ARI Forwarding Enable on preserved bridges PCI: liveupdate: Do not disable bus mastering on preserved devices during kexec to preserve certain configuration on bridges that have downstream endpoints that are being preserved. To support P2PDMA we will also have to preserve bridge memory windows (future series). If we are ok with applying those policies to all bridges on the system whenever one or more endpoints anywhere on the system are being preserved, then I agree we don't need this patch. But I thought it would be cleaner to track things per-device.