linux-kernel - [PATCH v3] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

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Date: Mon, 19 Feb 2024 12:24:22 +0100
From: Bean Huo <beanhuo@...pp.de>
To: bhelgaas@...gle.com,
	helgaas@...nel.org,
	sathyanarayanan.kuppuswamy@...ux.intel.com
Cc: linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bean Huo <beanhuo@...ron.com>,
	stable@...r.kernel.org
Subject: [PATCH v3] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

From: Bean Huo <beanhuo@...ron.com>

As per PCIe r6.2, sec 6.13 titled "Alternative Routing-ID Interpretation
(ARI)", up to 8 [fn # 0..7] Physical Functions(PFs) are allowed in an
non-ARI capable device. Previously, our implementation erroneously limited
the maximum number of PFs to 7 for endpoints without ARI support.

This patch corrects the maximum PF count to adhere to the PCIe specification
by allowing up to 8 PFs on non-ARI capable devices. This change ensures better
compliance with the standard and improves compatibility with devices relying
on this specification.

Fixes: c3df83e01a96 ("PCI: Clean up pci_scan_slot()")
Cc: stable@...r.kernel.org
Signed-off-by: Bean Huo <beanhuo@...ron.com>
---
Changelog:
	v2--v3:
		1. Update commit messag 
	v1--v2:
		1. Add Fixes tag
		2. Modify commit message
---
 drivers/pci/probe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ed6b7f48736a..8c3d0f63bc13 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2630,7 +2630,8 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
 	if (pci_ari_enabled(bus))
 		return next_ari_fn(bus, dev, fn);
 
-	if (fn >= 7)
+	/* If EP does not support ARI, the maximum number of functions should be 7 */
+	if (fn > 7)
 		return -ENODEV;
 	/* only multifunction devices may have more functions */
 	if (dev && !dev->multifunction)
-- 
2.34.1