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>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e07c432c731ff9a516fe8b23228af0fe6fa1d29a..9cf7b34f2db0c29273ca58a28b0c5683a273a0ae 100644 (file)
--- 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

diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 6e64aaf00d1dd9473fff8cfd0e6e09074a31443c..3a5261bdff5d42dd04384f75556618cb5ec5b4ad 100644 (file)
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -121,6 +121,21 @@ void __init dmi_check_skip_isa_align(void)
        dmi_check_system(can_skip_pciprobe_dmi_table);
 }
 
+static void __devinit pcibios_fixup_device_resources(struct pci_dev *dev)
+{
+       struct resource *rom_r = &dev->resource[PCI_ROM_RESOURCE];
+
+       if (pci_probe & PCI_NOASSIGN_ROMS) {
+               if (rom_r->parent)
+                       return;
+               if (rom_r->start) {
+                       /* we deal with BIOS assigned ROM later */
+                       return;
+               }
+               rom_r->start = rom_r->end = rom_r->flags = 0;
+       }
+}
+
 /*
  *  Called after each bus is probed, but before its children
  *  are examined.
@@ -128,7 +143,11 @@ void __init dmi_check_skip_isa_align(void)
 
 void __devinit  pcibios_fixup_bus(struct pci_bus *b)
 {
+       struct pci_dev *dev;
+
        pci_read_bridge_bases(b);
+       list_for_each_entry(dev, &b->devices, bus_list)
+               pcibios_fixup_device_resources(dev);
 }
 
 /*
@@ -483,6 +502,9 @@ char * __devinit  pcibios_setup(char *str)
        else if (!strcmp(str, "rom")) {
                pci_probe |= PCI_ASSIGN_ROMS;
                return NULL;
+       } else if (!strcmp(str, "norom")) {
+               pci_probe |= PCI_NOASSIGN_ROMS;
+               return NULL;
        } else if (!strcmp(str, "assign-busses")) {
                pci_probe |= PCI_ASSIGN_ALL_BUSSES;
                return NULL;

diff --git a/arch/x86/pci/pci.h b/arch/x86/pci/pci.h
index 720c4c55453462d78770d03506c26ae45d6d2edd..291dafec07b703026e500ab07d7b1e9645d217a9 100644 (file)
--- a/arch/x86/pci/pci.h
+++ b/arch/x86/pci/pci.h
@@ -27,6 +27,7 @@
 #define PCI_CAN_SKIP_ISA_ALIGN 0x8000
 #define PCI_USE__CRS           0x10000
 #define PCI_CHECK_ENABLE_AMD_MMCONF    0x20000
+#define PCI_NOASSIGN_ROMS      0x40000
 
 extern unsigned int pci_probe;
 extern unsigned long pirq_table_addr;