Re: Does kmalloc always return address below 4GB?

[David S. Miller]

   From: "Adam J. Richter" <[e-mail]>
   Date: Tue, 5 Mar 2002 09:08:20 -0800

   Steffen Persvold writes:
   >I know pci_map_single (and _sg) will
   >use bounce buffers on platforms without an IOMMU [...]
   
   	For a moment I thought that must be the point that I
   was missing, but I don't see any such bounce buffer support
   in linux-2.5.6-pre2/include/asm-i386/pci.h or arch/i386/kernel/pci-dma.c.
   I do not see how this is currently implemented on x86 systems with >4GB
   of RAM.

You won't get HIGHMEM pages in your driver unless you are using
2.5.x and tell the scsi layer you are capable to DMA to/from
HIGHMEM pages.

Similarly for networking drivers, and setting NETIF_F_HIGHDMA in
the net device feature flags.