x86: Detect whether we should use Xen SWIOTLB.

It is paramount that we call pci_xen_swiotlb_detect before
pci_swiotlb_detect as both implementations use the 'swiotlb'
and 'swiotlb_force' flags. The pci-xen_swiotlb_detect inhibits
the swiotlb_force and swiotlb flag so that the native SWIOTLB
implementation is not enabled when running under Xen.

[since v1 changed two Cc's to Acked-by]

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    [http://lkml.org/lkml/2010/7/27/374]
Cc: Albert Herranz <albert_herranz@yahoo.es>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
    [conditional http://lkml.org/lkml/2010/8/2/324]
Cc: x86@kernel.org
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 4b7e3d8b01dd..9f07cfcbd3a5 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -13,6 +13,7 @@
 #include <asm/calgary.h>
 #include <asm/amd_iommu.h>
 #include <asm/x86_init.h>
+#include <asm/xen/swiotlb-xen.h>
 
 static int forbid_dac __read_mostly;
 
@@ -132,7 +133,7 @@ void __init pci_iommu_alloc(void)
         /* free the range so iommu could get some range less than 4G */
         dma32_free_bootmem();
 
-        if (pci_swiotlb_detect())
+        if (pci_xen_swiotlb_detect() || pci_swiotlb_detect())
                 goto out;
 
         gart_iommu_hole_init();
@@ -144,6 +145,8 @@ void __init pci_iommu_alloc(void)
         /* needs to be called after gart_iommu_hole_init */
         amd_iommu_detect();
 out:
+        pci_xen_swiotlb_init();
+
         pci_swiotlb_init();
 }
 
@@ -296,7 +299,7 @@ static int __init pci_iommu_init(void)
 #endif
         x86_init.iommu.iommu_init();
 
-        if (swiotlb) {
+        if (swiotlb || xen_swiotlb) {
                 printk(KERN_INFO "PCI-DMA: "
                        "Using software bounce buffering for IO (SWIOTLB)\n");
                 swiotlb_print_info();