[PATCH] x86_64: Calgary IOMMU - introduce iommu_detected

swiotlb relies on the gart specific iommu_aperture variable to know if
we discovered a hardware IOMMU before swiotlb initialization.  Introduce
iommu_detected to do the same thing, but in a HW IOMMU neutral manner,
in preparation for adding the Calgary HW IOMMU.
Signed-Off-By: NMuli Ben-Yehuda <muli@il.ibm.com>
Signed-Off-By: NJon Mason <jdmason@us.ibm.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/aperture.c

@@ -209,6 +209,7 @@ void __init iommu_hole_init(void)
 		if (!early_is_k8_nb(read_pci_config(0, num, 3, 0x00)))
 			continue;
 
+		iommu_detected = 1;
 		iommu_aperture = 1; 
 
 		aper_order = (read_pci_config(0, num, 3, 0x90) >> 1) & 7; 

arch/x86_64/kernel/pci-dma.c

@@ -33,6 +33,9 @@ int panic_on_overflow __read_mostly = 0;
 int force_iommu __read_mostly= 0;
 #endif
 
+/* Set this to 1 if there is a HW IOMMU in the system */
+int iommu_detected __read_mostly = 0;
+
 /* Dummy device used for NULL arguments (normally ISA). Better would
    be probably a smaller DMA mask, but this is bug-to-bug compatible
    to i386. */

arch/x86_64/kernel/pci-gart.c

@@ -597,6 +597,10 @@ static int __init pci_iommu_init(void)
 	if (swiotlb)
 		return -ENODEV;
 
+	/* Did we detect a different HW IOMMU? */
+	if (iommu_detected && !iommu_aperture)
+		return -1;
+
 	if (no_iommu ||
 	    (!force_iommu && end_pfn <= MAX_DMA32_PFN) ||
 	    !iommu_aperture ||

arch/x86_64/kernel/pci-swiotlb.c

@@ -31,7 +31,7 @@ struct dma_mapping_ops swiotlb_dma_ops = {
 void pci_swiotlb_init(void)
 {
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
-	if (!iommu_aperture && !no_iommu &&
+	if (!iommu_detected && !no_iommu &&
 	    (end_pfn > MAX_DMA32_PFN || force_iommu))
 	       swiotlb = 1;
 	if (swiotlb) {

include/asm-x86_64/proto.h

@@ -116,6 +116,7 @@ extern int skip_ioapic_setup;
 extern int acpi_ht;
 extern int acpi_disabled;
 
+extern int iommu_detected;
 #ifdef CONFIG_IOMMU
 extern int fallback_aper_order;
 extern int fallback_aper_force;