[lkml]   [2005]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Subject64bit PCI IORESOURCE_MEM bugs
I am running linux with the memmap patch, on an Intel 64 bit 
machine with 16 Gigs of RAM. I have written a device driver that DMAs to 14
Gigs of RAM.

I am attempting to give 1 Gig of RAM to the OS and 1Gig of address space for
PCI addressing and 14 Gigs for my DMA. I have added the following to my
grub command line:
memmap=exactmap memmap=640K@0 memmap=1024M@1M memmap=2000M$2048M

This does not seam to be working. I think I have run into some bugs in the
kernel unless I am mistaken how physical RAM addressing and the bus
addressing work.

1) in arch/x86_64/kernel/e820.c the e820_reserve_resources function the
line if ([i].addr +[i].size > 0x100000000ULL) makes it so
any region that
starts below the 4Gig mark but ends above 4Gig mark is ignored. So I
have been forced to reserve the 15 Gigs using two different memmap calls one
that reserves memory below 4 Gigs and one that reserves the memory above 4

2) I am unable to get all of my PCI devices to move there addressing from
the default values to the hole I have given it. I am getting several errors
of the form: "PCI: Cannot allocate resource region 8 of bridge
0000:00:07.0". Some of my devices are moving to the proper location.
Neither the code in drivers/pci/probe.c pci_read_bases which gets the
default addresses for the resources or /arch/i386/pci/i386.c
pcibios_allocate_bus_resources check to see if the address that are being
used are reserved. They just attempt to allocate the memory and fail. It
seams like a check should be made in one of these functions and if the
resources are reserved then the addresses should be changed. (Note: 64 bit
uses the i386 pci code that is why I am pointing out potential errors in the
i386 code)

I also noticed the reserve kernel param can only take ints so large
addresses can not be reserved

Thank you,

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-07-07 02:07    [W:0.019 / U:6.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site