{"id":2221662,"url":"http://patchwork.ozlabs.org/api/patches/2221662/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/patch/20260410052918.5556-2-gloveless@jqluv.com/","project":{"id":28,"url":"http://patchwork.ozlabs.org/api/projects/28/?format=json","name":"Linux PCI development","link_name":"linux-pci","list_id":"linux-pci.vger.kernel.org","list_email":"linux-pci@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260410052918.5556-2-gloveless@jqluv.com>","list_archive_url":null,"date":"2026-04-10T05:26:02","name":"[v2] PCI: release empty sibling bridge windows during rebar expansion","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"a4719216f4eab14b591a1e1b7e151d335debcc3e","submitter":{"id":93094,"url":"http://patchwork.ozlabs.org/api/people/93094/?format=json","name":"Geramy Loveless","email":"gloveless@jqluv.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-pci/patch/20260410052918.5556-2-gloveless@jqluv.com/mbox/","series":[{"id":499396,"url":"http://patchwork.ozlabs.org/api/series/499396/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/list/?series=499396","date":"2026-04-10T05:26:02","name":"[v2] PCI: release empty sibling bridge windows during rebar expansion","version":2,"mbox":"http://patchwork.ozlabs.org/series/499396/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2221662/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2221662/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=jqluv-com.20251104.gappssmtp.com\n header.i=@jqluv-com.20251104.gappssmtp.com header.a=rsa-sha256\n header.s=20251104 header.b=w32qjMo3;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; helo=sea.lore.kernel.org;\n envelope-from=linux-pci+bounces-52260-incoming=patchwork.ozlabs.org@vger.kernel.org;\n receiver=patchwork.ozlabs.org)","smtp.subspace.kernel.org;\n\tdkim=pass (2048-bit key) header.d=jqluv-com.20251104.gappssmtp.com\n header.i=@jqluv-com.20251104.gappssmtp.com header.b=\"w32qjMo3\"","smtp.subspace.kernel.org;\n arc=none smtp.client-ip=74.125.82.44","smtp.subspace.kernel.org;\n dmarc=none (p=none dis=none) header.from=jqluv.com","smtp.subspace.kernel.org;\n spf=none smtp.mailfrom=jqluv.com"],"Received":["from sea.lore.kernel.org (sea.lore.kernel.org\n [IPv6:2600:3c0a:e001:db::12fc:5321])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fsQQF4y4Xz1yCv\n\tfor ; Fri, 10 Apr 2026 15:31:17 +1000 (AEST)","from smtp.subspace.kernel.org (conduit.subspace.kernel.org\n [100.90.174.1])\n\tby sea.lore.kernel.org (Postfix) with ESMTP id 5A08D300B06F\n\tfor ; Fri, 10 Apr 2026 05:30:57 +0000 (UTC)","from localhost.localdomain (localhost.localdomain [127.0.0.1])\n\tby smtp.subspace.kernel.org (Postfix) with ESMTP id BDE0130E838;\n\tFri, 10 Apr 2026 05:30:56 +0000 (UTC)","from mail-dl1-f44.google.com (mail-dl1-f44.google.com\n [74.125.82.44])\n\t(using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))\n\t(No client certificate requested)\n\tby smtp.subspace.kernel.org (Postfix) with ESMTPS id 0903C20010A\n\tfor ; Fri, 10 Apr 2026 05:30:54 +0000 (UTC)","by mail-dl1-f44.google.com with SMTP id\n a92af1059eb24-128e4d0cc48so8967658c88.1\n for ; Thu, 09 Apr 2026 22:30:54 -0700 (PDT)","from geramyl-MS-S1-MAX.. 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This prevents BAR resize on\ndevices behind multi-port PCIe switches (such as Thunderbolt docks)\nwhere empty sibling downstream ports hold small reservations that\nblock the parent bridge window from being freed and re-sized.\n\nAdd pci_bus_subtree_empty() to check whether a bus subtree contains\nany assigned device BARs, and pci_bus_release_empty_bridges() to\nrelease bridge window resources of empty sibling bridges, saving\nthem to the rollback list so failures can be properly unwound.\n\nIn pbus_reassign_bridge_resources(), call pci_bus_release_empty_bridges()\nbefore checking res->child, so empty sibling windows are cleared first\nand the parent window can then be released and grown.\n\nUses PCI bus/device iterators rather than walking the raw resource\ntree, which avoids issues with stale sibling pointers after resource\nrelease.\n\nSuggested-by: Ilpo Järvinen \nSigned-off-by: Geramy Loveless \n---\n drivers/pci/setup-bus.c | 99 ++++++++++++++++++++++++++++++++++++++++-\n 1 file changed, 97 insertions(+), 2 deletions(-)","diff":"diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c\nindex 4cf120ebe5a..7a182cd7e4d 100644\n--- a/drivers/pci/setup-bus.c\n+++ b/drivers/pci/setup-bus.c\n@@ -2292,6 +2292,94 @@ void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)\n }\n EXPORT_SYMBOL_GPL(pci_assign_unassigned_bridge_resources);\n \n+/*\n+ * pci_bus_subtree_empty - Check whether a bus subtree has any assigned\n+ * non-bridge device resources.\n+ * @bus: PCI bus to check\n+ *\n+ * Returns true if no device on @bus or its descendant buses has any\n+ * assigned BARs (bridge window resources are not considered).\n+ */\n+static bool pci_bus_subtree_empty(struct pci_bus *bus)\n+{\n+\tstruct pci_dev *dev;\n+\n+\tlist_for_each_entry(dev, &bus->devices, bus_list) {\n+\t\tstruct resource *r;\n+\t\tunsigned int i;\n+\n+\t\tpci_dev_for_each_resource(dev, r, i) {\n+\t\t\tif (i >= PCI_BRIDGE_RESOURCES)\n+\t\t\t\tbreak;\n+\t\t\tif (resource_assigned(r))\n+\t\t\t\treturn false;\n+\t\t}\n+\n+\t\tif (dev->subordinate &&\n+\t\t !pci_bus_subtree_empty(dev->subordinate))\n+\t\t\treturn false;\n+\t}\n+\n+\treturn true;\n+}\n+\n+/*\n+ * pci_bus_release_empty_bridges - Release bridge window resources of\n+ * empty sibling bridges so the parent window can be freed and re-sized.\n+ * @bus: PCI bus whose child bridges to scan\n+ * @b_win: Parent bridge window resource; only children of this window\n+ * are released\n+ * @saved: List to save released resources for rollback\n+ *\n+ * For each PCI-to-PCI bridge on @bus whose subtree is empty (no assigned\n+ * device BARs), releases bridge window resources that are children of\n+ * @b_win, saving them for rollback via @saved.\n+ *\n+ * Returns 0 on success, negative errno on failure.\n+ */\n+static int pci_bus_release_empty_bridges(struct pci_bus *bus,\n+\t\t\t\t\t struct resource *b_win,\n+\t\t\t\t\t struct list_head *saved)\n+{\n+\tstruct pci_dev *dev;\n+\n+\tlist_for_each_entry(dev, &bus->devices, bus_list) {\n+\t\tstruct resource *r;\n+\t\tunsigned int i;\n+\n+\t\tif (!dev->subordinate)\n+\t\t\tcontinue;\n+\n+\t\tif ((dev->class >> 8) != PCI_CLASS_BRIDGE_PCI)\n+\t\t\tcontinue;\n+\n+\t\tif (!pci_bus_subtree_empty(dev->subordinate))\n+\t\t\tcontinue;\n+\n+\t\tpci_dev_for_each_resource(dev, r, i) {\n+\t\t\tint ret;\n+\n+\t\t\tif (!pci_resource_is_bridge_win(i))\n+\t\t\t\tcontinue;\n+\n+\t\t\tif (!resource_assigned(r))\n+\t\t\t\tcontinue;\n+\n+\t\t\tif (r->parent != b_win)\n+\t\t\t\tcontinue;\n+\n+\t\t\tret = pci_dev_res_add_to_list(saved, dev, r, 0, 0);\n+\t\t\tif (ret)\n+\t\t\t\treturn ret;\n+\n+\t\t\trelease_child_resources(r);\n+\t\t\tpci_release_resource(dev, i);\n+\t\t}\n+\t}\n+\n+\treturn 0;\n+}\n+\n /*\n * Walk to the root bus, find the bridge window relevant for @res and\n * release it when possible. If the bridge window contains assigned\n@@ -2316,7 +2404,14 @@ static int pbus_reassign_bridge_resources(struct pci_bus *bus, struct resource *\n \n \t\ti = pci_resource_num(bridge, res);\n \n-\t\t/* Ignore BARs which are still in use */\n+\t\t/* Release empty sibling bridge windows first */\n+\t\tif (bridge->subordinate) {\n+\t\t\tret = pci_bus_release_empty_bridges(\n+\t\t\t\t\tbridge->subordinate, res, saved);\n+\t\t\tif (ret)\n+\t\t\t\treturn ret;\n+\t\t}\n+\n \t\tif (!res->child) {\n \t\t\tret = pci_dev_res_add_to_list(saved, bridge, res, 0, 0);\n \t\t\tif (ret)\n@@ -2327,7 +2422,7 @@ static int pbus_reassign_bridge_resources(struct pci_bus *bus, struct resource *\n \t\t\tconst char *res_name = pci_resource_name(bridge, i);\n \n \t\t\tpci_warn(bridge,\n-\t\t\t\t \"%s %pR: was not released (still contains assigned resources)\\n\",\n+\t\t\t\t \"%s %pR: not released, active children present\\n\",\n \t\t\t\t res_name, res);\n \t\t}\n \n","prefixes":["v2"]}