linux-kernel - [PATCH v2] PCI: Fix BUILD_BUG

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Message-ID: <20250212185337.293023-1-alex.williamson@redhat.com>
Date: Wed, 12 Feb 2025 11:53:32 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: bhelgaas@...gle.com
Cc: Alex Williamson <alex.williamson@...hat.com>,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mitchell.augustin@...onical.com,
	ilpo.jarvinen@...ux.intel.com,
	david.laight.linux@...il.com,
	Oleg Nesterov <oleg@...hat.com>
Subject: [PATCH v2] PCI: Fix BUILD_BUG_ON usage for old gcc

As reported in the below link, it seems older versions of gcc cannot
determine that the howmany variable is known for all callers.  Include
a test so that newer compilers can enforce this sanity check and older
compilers can still work.  Add __always_inline attribute to give the
compiler an even better chance to know the inputs.

Fixes: 4453f360862e ("PCI: Batch BAR sizing operations")
Link: https://lore.kernel.org/all/20250209154512.GA18688@redhat.com
Reported-by: Oleg Nesterov <oleg@...hat.com>
Tested-by: Oleg Nesterov <oleg@...hat.com>
Tested-by: Mitchell Augustin <mitchell.augustin@...onical.com>
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---

v2:
 - Switch to statically_true (David Laight)
 - Add __always_inline (David Laight)
 - Included Tested-by reports

 drivers/pci/probe.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b6536ed599c3..246744d8d268 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -339,13 +339,14 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type,
 	return (res->flags & IORESOURCE_MEM_64) ? 1 : 0;
 }
 
-static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
+static __always_inline void pci_read_bases(struct pci_dev *dev,
+					   unsigned int howmany, int rom)
 {
 	u32 rombar, stdbars[PCI_STD_NUM_BARS];
 	unsigned int pos, reg;
 	u16 orig_cmd;
 
-	BUILD_BUG_ON(howmany > PCI_STD_NUM_BARS);
+	BUILD_BUG_ON(statically_true(howmany > PCI_STD_NUM_BARS));
 
 	if (dev->non_compliant_bars)
 		return;
-- 
2.48.1