linux-kernel - [RFC PATCH 4/6] x86: PCI: preserve IORESOURCE

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Message-ID: <20240709133610.1089420-5-stewart.hildebrand@amd.com>
Date: Tue, 9 Jul 2024 09:36:01 -0400
From: Stewart Hildebrand <stewart.hildebrand@....com>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>
CC: Stewart Hildebrand <stewart.hildebrand@....com>, <x86@...nel.org>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 4/6] x86: PCI: preserve IORESOURCE_STARTALIGN alignment

Currently, it's not possible to use the IORESOURCE_STARTALIGN flag on
x86 due to the alignment being overwritten in
pcibios_allocate_dev_resources(). Make one small change in arch/x86 to
make it work on x86.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@....com>
---
RFC: We don't have enough info in this function to re-calculate the
     alignment value in case of IORESOURCE_STARTALIGN. Luckily our
     alignment value seems to be intact, so just don't touch it...
     Alternatively, we could call pci_reassigndev_resource_alignment()
     after the loop. Would that be preferable?
---
 arch/x86/pci/i386.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index f2f4a5d50b27..ff6e61389ec7 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -283,8 +283,11 @@ static void pcibios_allocate_dev_resources(struct pci_dev *dev, int pass)
 						/* We'll assign a new address later */
 						pcibios_save_fw_addr(dev,
 								idx, r->start);
-						r->end -= r->start;
-						r->start = 0;
+						if (!(r->flags &
+						      IORESOURCE_STARTALIGN)) {
+							r->end -= r->start;
+							r->start = 0;
+						}
 					}
 				}
 			}
-- 
2.45.2