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authorGary Hade <garyhade@us.ibm.com>2008-05-12 13:57:46 -0700
committerJesse Barnes <jbarnes@virtuousgeek.org>2008-06-10 10:59:50 -0700
commitbb71ad880204b79d60331d3384103976e086cb9f (patch)
tree612b14aed172db36ddbdae2287ffdd65e6baef00 /Documentation
parent5ca5c02f0e81c094c19d30dc0d13be4e929a994a (diff)
downloadop-kernel-dev-bb71ad880204b79d60331d3384103976e086cb9f.zip
op-kernel-dev-bb71ad880204b79d60331d3384103976e086cb9f.tar.gz
PCI: boot parameter to avoid expansion ROM memory allocation
Contention for scarce PCI memory resources has been growing due to an increasing number of PCI slots in large multi-node systems. The kernel currently attempts by default to allocate memory for all PCI expansion ROMs so there has also been an increasing number of PCI memory allocation failures seen on these systems. This occurs because the BIOS either (1) provides insufficient PCI memory resource for all the expansion ROMs or (2) provides adequate PCI memory resource for expansion ROMs but provides the space in kernel unexpected BIOS assigned P2P non-prefetch windows. The resulting PCI memory allocation failures may be benign when related to memory requests for expansion ROMs themselves but in some cases they can occur when attempting to allocate space for more critical BARs. This can happen when a successful expansion ROM allocation request consumes memory resource that was intended for a non-ROM BAR. We have seen this happen during PCI hotplug of an adapter that contains a P2P bridge where successful memory allocation for an expansion ROM BAR on device behind the bridge consumed memory that was intended for a non-ROM BAR on the P2P bridge. In all cases the allocation failure messages can be very confusing for users. This patch provides a new 'pci=norom' kernel boot parameter that can be used to disable the default PCI expansion ROM memory resource allocation. This provides a way to avoid the above described issues on systems that do not contain PCI devices for which drivers or user-level applications depend on the default PCI expansion ROM memory resource allocation behavior. Signed-off-by: Gary Hade <garyhade@us.ibm.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e07c432..9cf7b34 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1496,6 +1496,9 @@ and is between 256 and 4096 characters. It is defined in the file
Use with caution as certain devices share
address decoders between ROMs and other
resources.
+ norom [X86-32,X86_64] Do not assign address space to
+ expansion ROMs that do not already have
+ BIOS assigned address ranges.
irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
assigned automatically to PCI devices. You can
make the kernel exclude IRQs of your ISA cards
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