linux-kernel - [PATCH] drivers/pci: Allow attaching AER to non-RP devices that support MSI

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Message-ID: <20251128122053.35909-1-darnshah@amazon.de>
Date: Fri, 28 Nov 2025 12:20:53 +0000
From: Darshit Shah <darnshah@...zon.de>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Lukas Wunner <lukas@...ner.de>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>, "Kuppuswamy
 Sathyanarayanan" <sathyanarayanan.kuppuswamy@...ux.intel.com>, "Jonathan
 Cameron" <Jonthan.Cameron@...wei.com>, Darshit Shah <darnshah@...zon.de>,
	<darnir@....org>, Feng Tang <feng.tang@...ux.alibaba.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<nh-open-source@...zon.com>
Subject: [PATCH] drivers/pci: Allow attaching AER to non-RP devices that support MSI

Previously portdrv tried to prevent non-Root Port (RP) and non-Root
Complex Event Collector (RCEC) devices from enabling AER capability.
This was done because some switches enable AER but do not support MSI.
Hence, trying to initialize the AER IRQ for such devices would fail and
Linux would fail to claim the switch port entirely.

However, it is possible to have switches upstream of an endpoint that
support MSI and AER. Without AER capability being enabled on such
a switch, portdrv will refuse to enable the DPC capability as well,
preventing a PCIe error on an endpoint from being handled by the switch.

Allow enabling the AER service on non-RP, non-RCEC devices if they still
support both AER and MSI. This allows switches upstream of an endpoint
to generate and handle DPC events.
Fixes: d8d2b65a940b ("PCI/portdrv: Allow AER service only for Root Ports & RCECs")
Signed-off-by: Darshit Shah <darnshah@...zon.de>
---
 drivers/pci/pcie/portdrv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
index d1b68c18444f..41326bbcd295 100644
--- a/drivers/pci/pcie/portdrv.c
+++ b/drivers/pci/pcie/portdrv.c
@@ -237,8 +237,8 @@ static int get_port_device_capability(struct pci_dev *dev)
 	}

 #ifdef CONFIG_PCIEAER
-	if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
-             pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC) &&
+	if ((dev->msi_cap || pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
+	     pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC) &&
 	    dev->aer_cap && pci_aer_available() &&
 	    (pcie_ports_native || host->native_aer))
 		services |= PCIE_PORT_SERVICE_AER;
-- 
2.47.3

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