From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE6A6155333 for ; Sat, 16 Aug 2025 03:50:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755316224; cv=none; b=KFRolbugNqyrIzXi8hS3sJyJtPIR0ltzio5+O9DU0niJTMfbLsEm8eiiX28lvGfpazw0O6LId8Px5t0wmA/g4zt3SLQDpwVC2rKtqguCIvJa2T0czuUq1wgC3Lf4zmE7JxzsLiT5icDbOtDgezoU9K1V2tgbvfIgSgqFquP+7XY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755316224; c=relaxed/simple; bh=oDnhr//78QsVOOwn9Ovb8LghFEQC6iflpHNd23TQA4E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oqTdLahQbCebBf/HMtYuxyYg0paEQhDsdgyOqGO9+njs9J7PRN7f1jeHBpKxXSVbNu+e/Cq35MW+gb8BGoRxMmoqDnig36QOlE5xwzpAyTn9EY5zYkoZ7vequCVzbLL9YWHgWohpgukLo4ZNwlG2kUCTNrwiRd9LiZYsxZKy6/0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hq/pRUii; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hq/pRUii" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70095C4CEEF; Sat, 16 Aug 2025 03:50:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755316224; bh=oDnhr//78QsVOOwn9Ovb8LghFEQC6iflpHNd23TQA4E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hq/pRUiisRztKFECgP5KqYHBL0D8VWmwlZ1Owzv06MSG7tBfvMMBbsoElq9fvGWmq G7VVcv5L7iaGXoGHbHfBCHZqB6O3exW9ajCDxUtq/s25aBDffTeMFr8M/1NQmEedsB YV5HAAJP/APV/U8EttHxAzV1JJSUIpSgdgqc+7NLLiP9MkIqP/e5HU3HaXGJWAlARS lVG9S2aY5235zwZLLOmL3yuDRZZNtqZ9DuORP/8qMb5csq/WEgx63DfO/orLMXBlgp AC8+RGheIifqzqY5qgn3EmbU8zcLK3iPYIflepI5AcBGDF6cxklxdUgNkS+1nz8Uoh UwJLIxeOdy7iA== From: Sasha Levin To: stable@vger.kernel.org Cc: Lukas Wunner , Laurent Bigonville , Mario Limonciello , Bjorn Helgaas , "Rafael J. Wysocki" , Sasha Levin Subject: [PATCH 6.6.y] PCI/ACPI: Fix runtime PM ref imbalance on Hot-Plug Capable ports Date: Fri, 15 Aug 2025 23:50:20 -0400 Message-ID: <20250816035021.666925-1-sashal@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <2025081509-uncrown-janitor-adad@gregkh> References: <2025081509-uncrown-janitor-adad@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Lukas Wunner [ Upstream commit 6cff20ce3b92ffbf2fc5eb9e5a030b3672aa414a ] pci_bridge_d3_possible() is called from both pcie_portdrv_probe() and pcie_portdrv_remove() to determine whether runtime power management shall be enabled (on probe) or disabled (on remove) on a PCIe port. The underlying assumption is that pci_bridge_d3_possible() always returns the same value, else a runtime PM reference imbalance would occur. That assumption is not given if the PCIe port is inaccessible on remove due to hot-unplug: pci_bridge_d3_possible() calls pciehp_is_native(), which accesses Config Space to determine whether the port is Hot-Plug Capable. An inaccessible port returns "all ones", which is converted to "all zeroes" by pcie_capability_read_dword(). Hence the port no longer seems Hot-Plug Capable on remove even though it was on probe. The resulting runtime PM ref imbalance causes warning messages such as: pcieport 0000:02:04.0: Runtime PM usage count underflow! Avoid the Config Space access (and thus the runtime PM ref imbalance) by caching the Hot-Plug Capable bit in struct pci_dev. The struct already contains an "is_hotplug_bridge" flag, which however is not only set on Hot-Plug Capable PCIe ports, but also Conventional PCI Hot-Plug bridges and ACPI slots. The flag identifies bridges which are allocated additional MMIO and bus number resources to allow for hierarchy expansion. The kernel is somewhat sloppily using "is_hotplug_bridge" in a number of places to identify Hot-Plug Capable PCIe ports, even though the flag encompasses other devices. Subsequent commits replace these occurrences with the new flag to clearly delineate Hot-Plug Capable PCIe ports from other kinds of hotplug bridges. Document the existing "is_hotplug_bridge" and the new "is_pciehp" flag and document the (non-obvious) requirement that pci_bridge_d3_possible() always returns the same value across the entire lifetime of a bridge, including its hot-removal. Fixes: 5352a44a561d ("PCI: pciehp: Make pciehp_is_native() stricter") Reported-by: Laurent Bigonville Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220216 Reported-by: Mario Limonciello Closes: https://lore.kernel.org/r/20250609020223.269407-3-superm1@kernel.org/ Link: https://lore.kernel.org/all/20250620025535.3425049-3-superm1@kernel.org/T/#u Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Acked-by: Rafael J. Wysocki Cc: stable@vger.kernel.org # v4.18+ Link: https://patch.msgid.link/fe5dcc3b2e62ee1df7905d746bde161eb1b3291c.1752390101.git.lukas@wunner.de [ changed "recent enough PCIe ports" comment to "some PCIe ports" ] Signed-off-by: Sasha Levin --- drivers/pci/pci-acpi.c | 4 +--- drivers/pci/pci.c | 8 ++++++-- drivers/pci/probe.c | 2 +- include/linux/pci.h | 10 +++++++++- 4 files changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c index 05b7357bd258..61bded8623d2 100644 --- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -793,13 +793,11 @@ int pci_acpi_program_hp_params(struct pci_dev *dev) bool pciehp_is_native(struct pci_dev *bridge) { const struct pci_host_bridge *host; - u32 slot_cap; if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE)) return false; - pcie_capability_read_dword(bridge, PCI_EXP_SLTCAP, &slot_cap); - if (!(slot_cap & PCI_EXP_SLTCAP_HPC)) + if (!bridge->is_pciehp) return false; if (pcie_ports_native) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 4541dfbf0e1b..dae6a0e83bf0 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3065,8 +3065,12 @@ static const struct dmi_system_id bridge_d3_blacklist[] = { * pci_bridge_d3_possible - Is it possible to put the bridge into D3 * @bridge: Bridge to check * - * This function checks if it is possible to move the bridge to D3. - * Currently we only allow D3 for recent enough PCIe ports and Thunderbolt. + * Currently we only allow D3 for some PCIe ports and for Thunderbolt. + * + * Return: Whether it is possible to move the bridge to D3. + * + * The return value is guaranteed to be constant across the entire lifetime + * of the bridge, including its hot-removal. */ bool pci_bridge_d3_possible(struct pci_dev *bridge) { diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index b7cec139d816..5557290b63dc 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1594,7 +1594,7 @@ void set_pcie_hotplug_bridge(struct pci_dev *pdev) pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, ®32); if (reg32 & PCI_EXP_SLTCAP_HPC) - pdev->is_hotplug_bridge = 1; + pdev->is_hotplug_bridge = pdev->is_pciehp = 1; } static void set_pcie_thunderbolt(struct pci_dev *dev) diff --git a/include/linux/pci.h b/include/linux/pci.h index 2d1fb935a8c8..ac5bd1718af2 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -318,7 +318,14 @@ struct pci_sriov; struct pci_p2pdma; struct rcec_ea; -/* The pci_dev structure describes PCI devices */ +/* struct pci_dev - describes a PCI device + * + * @is_hotplug_bridge: Hotplug bridge of any kind (e.g. PCIe Hot-Plug Capable, + * Conventional PCI Hot-Plug, ACPI slot). + * Such bridges are allocated additional MMIO and bus + * number resources to allow for hierarchy expansion. + * @is_pciehp: PCIe Hot-Plug Capable bridge. + */ struct pci_dev { struct list_head bus_list; /* Node in per-bus list */ struct pci_bus *bus; /* Bus this device is on */ @@ -439,6 +446,7 @@ struct pci_dev { unsigned int is_physfn:1; unsigned int is_virtfn:1; unsigned int is_hotplug_bridge:1; + unsigned int is_pciehp:1; unsigned int shpc_managed:1; /* SHPC owned by shpchp */ unsigned int is_thunderbolt:1; /* Thunderbolt controller */ /* -- 2.50.1