[PATCH] x86_64: Use function pointers to call DMA mapping functions

AK: I hacked Muli's original patch a lot and there were a lot
of changes - all bugs are probably to blame on me now.
There were also some changes in the fall back behaviour
for swiotlb - in particular it doesn't try to use GFP_DMA
now anymore. Also all DMA mapping operations use the
same core dma_alloc_coherent code with proper fallbacks now.
And various other changes and cleanups.

Known problems: iommu=force swiotlb=force together breaks
                needs more testing.

This patch cleans up x86_64's DMA mapping dispatching code. Right now
we have three possible IOMMU types: AGP GART, swiotlb and nommu, and
in the future we will also have Xen's x86_64 swiotlb and other HW
IOMMUs for x86_64. In order to support all of them cleanly, this
patch:

- introduces a struct dma_mapping_ops with function pointers for each
  of the DMA mapping operations of gart (AMD HW IOMMU), swiotlb
  (software IOMMU) and nommu (no IOMMU).

- gets rid of:

  if (swiotlb)
      return swiotlb_xxx();

- PCI_DMA_BUS_IS_PHYS is now checked against the dma_ops being set
This makes swiotlb faster by avoiding double copying in some cases.

Signed-Off-By: Muli Ben-Yehuda <mulix@mulix.org>
Signed-Off-By: Jon D. Mason <jdmason@us.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 13 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 150e1ac0bfed..ee053e32a721 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -351,32 +351,24 @@ config HPET_EMULATE_RTC
         depends on HPET_TIMER && RTC=y
 
 config GART_IOMMU
-        bool "IOMMU support"
+        bool "K8 GART IOMMU support"
         default y
+        select SWIOTLB
         depends on PCI
         help
           Support the IOMMU. Needed to run systems with more than 3GB of memory
           properly with 32-bit PCI devices that do not support DAC (Double Address
           Cycle). The IOMMU can be turned off at runtime with the iommu=off parameter.
           Normally the kernel will take the right choice by itself.
-          This option includes a driver for the AMD Opteron/Athlon64 IOMMU
-          and a software emulation used on some other systems.
+          This option includes a driver for the AMD Opteron/Athlon64 northbridge IOMMU
+          and a software emulation used on other systems.
           If unsure, say Y.
 
 # need this always enabled with GART_IOMMU for the VIA workaround
 config SWIOTLB
-       bool
-       depends on GART_IOMMU
-       default y
-
-config DUMMY_IOMMU
         bool
-        depends on !GART_IOMMU && !SWIOTLB
         default y
-        help
-          Don't use IOMMU code. This will cause problems when you have more than 4GB
-          of memory and any 32-bit devices. Don't turn on unless you know what you
-          are doing.
+        depends on GART_IOMMU
 
 config X86_MCE
         bool "Machine check support" if EMBEDDED