linux-kernel - [PATCH v2] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

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Date: Fri, 16 Feb 2024 20:01:13 +0100
From: Bean Huo <beanhuo@...pp.de>
To: bhelgaas@...gle.com,
	schnelle@...ux.ibm.com,
	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 v2] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices

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

The PCIe specification allows up to 8 Physical Functions (PFs) per endpoint
when ARI (Alternative Routing-ID Interpretation) is not supported. 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 endpoints. This change ensures better
compliance with the standard and improves compatibility with devices relying
on this specification.

The necessity for this adjustment was verified by a thorough review of the
"Alternative Routing-ID Interpretation (ARI)" section in the PCIe 3.0 Spec,
which first introduced ARI.

Fixes: c3df83e01a96 ("PCI: Clean up pci_scan_slot()")
Cc: stable@...r.kernel.org
Signed-off-by: Bean Huo <beanhuo@...ron.com>
---
Changelog:
	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