linux-kernel - Re: [PATCH] PCI: boot parameter to avoid expansion ROM memory allocation

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Message-ID: <86802c440805121443r43cc7ceay4c05625f2878172e@mail.gmail.com>
Date:	Mon, 12 May 2008 14:43:44 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Gary Hade" <garyhade@...ibm.com>
Cc:	jbarnes@...tuousgeek.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI: boot parameter to avoid expansion ROM memory allocation

On Mon, May 12, 2008 at 1:57 PM, Gary Hade <garyhade@...ibm.com> wrote:
> From: Gary Hade <garyhade@...ibm.com>
>
>  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@...ibm.com>
>  ---
>
>  --- linux-2.6.26-rc2/arch/x86/pci/pci.h.orig    2008-05-12 10:53:04.000000000 -0700
>  +++ linux-2.6.26-rc2/arch/x86/pci/pci.h 2008-05-12 10:54:39.000000000 -0700
>  @@ -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;
>  --- linux-2.6.26-rc2/Documentation/kernel-parameters.txt.orig   2008-05-12 10:55:30.000000000 -0700
>  +++ linux-2.6.26-rc2/Documentation/kernel-parameters.txt        2008-05-12 10:57:49.000000000 -0700
>  @@ -1493,6 +1493,9 @@ and is between 256 and 4096 characters.
>                                 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
>  --- linux-2.6.26-rc2/arch/x86/pci/common.c.orig 2008-05-12 10:59:58.000000000 -0700
>  +++ linux-2.6.26-rc2/arch/x86/pci/common.c      2008-05-12 11:22:05.000000000 -0700
>  @@ -121,6 +121,21 @@ void __init dmi_check_skip_isa_align(voi
>         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(voi
>
>   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);
>   }

or put check
+       if (pci_probe & PCI_NOASSIGN_ROMS) {

out of loop?

YH
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