18 files changed, 344 insertions, 57 deletions

diff --git a/arch/ia64/include/asm/iommu_table.h b/arch/ia64/include/asm/iommu_table.h
new file mode 100644
index 000000000000..92c8d36ae5ae
--- /dev/null
+++ b/arch/ia64/include/asm/iommu_table.h
@@ -0,0 +1,6 @@
+#ifndef _ASM_IA64_IOMMU_TABLE_H
+#define _ASM_IA64_IOMMU_TABLE_H
+
+#define IOMMU_INIT_POST(_detect)
+
+#endif /* _ASM_IA64_IOMMU_TABLE_H */
diff --git a/arch/x86/include/asm/amd_iommu.h b/arch/x86/include/asm/amd_iommu.h
index f16a2caca1e0..a6863a2dec1f 100644
--- a/arch/x86/include/asm/amd_iommu.h
+++ b/arch/x86/include/asm/amd_iommu.h
@@ -24,11 +24,11 @@
 
 #ifdef CONFIG_AMD_IOMMU
 
-extern void amd_iommu_detect(void);
+extern int amd_iommu_detect(void);
 
 #else
 
-static inline void amd_iommu_detect(void) { }
+static inline int amd_iommu_detect(void) { return -ENODEV; }
 
 #endif
 
diff --git a/arch/x86/include/asm/calgary.h b/arch/x86/include/asm/calgary.h
index 0918654305af..0d467b338835 100644
--- a/arch/x86/include/asm/calgary.h
+++ b/arch/x86/include/asm/calgary.h
@@ -62,9 +62,9 @@ struct cal_chipset_ops {
 extern int use_calgary;
 
 #ifdef CONFIG_CALGARY_IOMMU
-extern void detect_calgary(void);
+extern int detect_calgary(void);
 #else
-static inline void detect_calgary(void) { return; }
+static inline int detect_calgary(void) { return -ENODEV; }
 #endif
 
 #endif /* _ASM_X86_CALGARY_H */
diff --git a/arch/x86/include/asm/gart.h b/arch/x86/include/asm/gart.h
index bf357f9b25f0..43085bfc99c3 100644
--- a/arch/x86/include/asm/gart.h
+++ b/arch/x86/include/asm/gart.h
@@ -37,7 +37,7 @@ extern int gart_iommu_aperture_disabled;
 extern void early_gart_iommu_check(void);
 extern int gart_iommu_init(void);
 extern void __init gart_parse_options(char *);
-extern void gart_iommu_hole_init(void);
+extern int gart_iommu_hole_init(void);
 
 #else
 #define gart_iommu_aperture            0
@@ -50,8 +50,9 @@ static inline void early_gart_iommu_check(void)
 static inline void gart_parse_options(char *options)
 {
 }
-static inline void gart_iommu_hole_init(void)
+static inline int gart_iommu_hole_init(void)
 {
+        return -ENODEV;
 }
 #endif
 
diff --git a/arch/x86/include/asm/iommu_table.h b/arch/x86/include/asm/iommu_table.h
new file mode 100644
index 000000000000..f229b13a5f30
--- /dev/null
+++ b/arch/x86/include/asm/iommu_table.h
@@ -0,0 +1,100 @@
+#ifndef _ASM_X86_IOMMU_TABLE_H
+#define _ASM_X86_IOMMU_TABLE_H
+
+#include <asm/swiotlb.h>
+
+/*
+ * History lesson:
+ * The execution chain of IOMMUs in 2.6.36 looks as so:
+ *
+ *            [xen-swiotlb]
+ *                 |
+ *         +----[swiotlb *]--+
+ *        /         |         \
+ *       /          |          \
+ *    [GART]     [Calgary]  [Intel VT-d]
+ *     /
+ *    /
+ * [AMD-Vi]
+ *
+ * *: if SWIOTLB detected 'iommu=soft'/'swiotlb=force' it would skip
+ * over the rest of IOMMUs and unconditionally initialize the SWIOTLB.
+ * Also it would surreptitiously initialize set the swiotlb=1 if there were
+ * more than 4GB and if the user did not pass in 'iommu=off'. The swiotlb
+ * flag would be turned off by all IOMMUs except the Calgary one.
+ *
+ * The IOMMU_INIT* macros allow a similar tree (or more complex if desired)
+ * to be built by defining who we depend on.
+ *
+ * And all that needs to be done is to use one of the macros in the IOMMU
+ * and the pci-dma.c will take care of the rest.
+ */
+
+struct iommu_table_entry {
+        initcall_t      detect;
+        initcall_t      depend;
+        void            (*early_init)(void); /* No memory allocate available. */
+        void            (*late_init)(void); /* Yes, can allocate memory. */
+#define IOMMU_FINISH_IF_DETECTED (1<<0)
+#define IOMMU_DETECTED           (1<<1)
+        int             flags;
+};
+/*
+ * Macro fills out an entry in the .iommu_table that is equivalent
+ * to the fields that 'struct iommu_table_entry' has. The entries
+ * that are put in the .iommu_table section are not put in any order
+ * hence during boot-time we will have to resort them based on
+ * dependency. */
+
+
+#define __IOMMU_INIT(_detect, _depend, _early_init, _late_init, _finish)\
+        static const struct iommu_table_entry const                     \
+                __iommu_entry_##_detect __used                          \
+        __attribute__ ((unused, __section__(".iommu_table"),            \
+                        aligned((sizeof(void *)))))     \
+        = {_detect, _depend, _early_init, _late_init,                   \
+           _finish ? IOMMU_FINISH_IF_DETECTED : 0}
+/*
+ * The simplest IOMMU definition. Provide the detection routine
+ * and it will be run after the SWIOTLB and the other IOMMUs
+ * that utilize this macro. If the IOMMU is detected (ie, the
+ * detect routine returns a positive value), the other IOMMUs
+ * are also checked. You can use IOMMU_INIT_POST_FINISH if you prefer
+ * to stop detecting the other IOMMUs after yours has been detected.
+ */
+#define IOMMU_INIT_POST(_detect)                                        \
+        __IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  0, 0, 0)
+
+#define IOMMU_INIT_POST_FINISH(detect)                                  \
+        __IOMMU_INIT(_detect, pci_swiotlb_detect_4gb,  0, 0, 1)
+
+/*
+ * A more sophisticated version of IOMMU_INIT. This variant requires:
+ *  a). A detection routine function.
+ *  b). The name of the detection routine we depend on to get called
+ *      before us.
+ *  c). The init routine which gets called if the detection routine
+ *      returns a positive value from the pci_iommu_alloc. This means
+ *      no presence of a memory allocator.
+ *  d). Similar to the 'init', except that this gets called from pci_iommu_init
+ *      where we do have a memory allocator.
+ *
+ * The standard vs the _FINISH differs in that the _FINISH variant will
+ * continue detecting other IOMMUs in the call list after the
+ * the detection routine returns a positive number. The _FINISH will
+ * stop the execution chain. Both will still call the 'init' and
+ * 'late_init' functions if they are set.
+ */
+#define IOMMU_INIT_FINISH(_detect, _depend, _init, _late_init)          \
+        __IOMMU_INIT(_detect, _depend, _init, _late_init, 1)
+
+#define IOMMU_INIT(_detect, _depend, _init, _late_init)                 \
+        __IOMMU_INIT(_detect, _depend, _init, _late_init, 0)
+
+void sort_iommu_table(struct iommu_table_entry *start,
+                      struct iommu_table_entry *finish);
+
+void check_iommu_entries(struct iommu_table_entry *start,
+                         struct iommu_table_entry *finish);
+
+#endif /* _ASM_X86_IOMMU_TABLE_H */
diff --git a/arch/x86/include/asm/swiotlb.h b/arch/x86/include/asm/swiotlb.h
index 8085277e1b8b..977f1761a25d 100644
--- a/arch/x86/include/asm/swiotlb.h
+++ b/arch/x86/include/asm/swiotlb.h
@@ -5,17 +5,26 @@
 
 #ifdef CONFIG_SWIOTLB
 extern int swiotlb;
-extern int __init pci_swiotlb_detect(void);
+extern int __init pci_swiotlb_detect_override(void);
+extern int __init pci_swiotlb_detect_4gb(void);
 extern void __init pci_swiotlb_init(void);
+extern void __init pci_swiotlb_late_init(void);
 #else
 #define swiotlb 0
-static inline int pci_swiotlb_detect(void)
+static inline int pci_swiotlb_detect_override(void)
+{
+        return 0;
+}
+static inline int pci_swiotlb_detect_4gb(void)
 {
         return 0;
 }
 static inline void pci_swiotlb_init(void)
 {
 }
+static inline void pci_swiotlb_late_init(void)
+{
+}
 #endif
 
 static inline void dma_mark_clean(void *addr, size_t size) {}
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 80a93dc99076..2c833d8c4141 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -45,6 +45,7 @@ obj-y			+= bootflag.o e820.o
 obj-y                   += pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
 obj-y                   += alternative.o i8253.o pci-nommu.o hw_breakpoint.o
 obj-y                   += tsc.o io_delay.o rtc.o
+obj-y                   += pci-iommu_table.o
 
 obj-$(CONFIG_X86_TRAMPOLINE)    += trampoline.o
 obj-y                           += process.o
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 3cb482e123de..6e11c8134158 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -31,7 +31,7 @@
 #include <asm/iommu.h>
 #include <asm/gart.h>
 #include <asm/x86_init.h>
-
+#include <asm/iommu_table.h>
 /*
  * definitions for the ACPI scanning code
  */
@@ -1499,13 +1499,13 @@ static int __init early_amd_iommu_detect(struct acpi_table_header *table)
         return 0;
 }
 
-void __init amd_iommu_detect(void)
+int __init amd_iommu_detect(void)
 {
         if (no_iommu || (iommu_detected && !gart_iommu_aperture))
-                return;
+                return -ENODEV;
 
         if (amd_iommu_disabled)
-                return;
+                return -ENODEV;
 
         if (acpi_table_parse("IVRS", early_amd_iommu_detect) == 0) {
                 iommu_detected = 1;
@@ -1514,7 +1514,9 @@ void __init amd_iommu_detect(void)
 
                 /* Make sure ACS will be enabled */
                 pci_request_acs();
+                return 1;
         }
+        return -ENODEV;
 }
 
 /****************************************************************************
@@ -1545,3 +1547,8 @@ static int __init parse_amd_iommu_options(char *str)
 
 __setup("amd_iommu_dump", parse_amd_iommu_dump);
 __setup("amd_iommu=", parse_amd_iommu_options);
+
+IOMMU_INIT_FINISH(amd_iommu_detect,
+                  gart_iommu_hole_init,
+                  0,
+                  0);
diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index 377f5db3b8b4..b3a16e8f0703 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -371,7 +371,7 @@ void __init early_gart_iommu_check(void)
 
 static int __initdata printed_gart_size_msg;
 
-void __init gart_iommu_hole_init(void)
+int __init gart_iommu_hole_init(void)
 {
         u32 agp_aper_base = 0, agp_aper_order = 0;
         u32 aper_size, aper_alloc = 0, aper_order = 0, last_aper_order = 0;
@@ -381,7 +381,7 @@ void __init gart_iommu_hole_init(void)
 
         if (gart_iommu_aperture_disabled || !fix_aperture ||
             !early_pci_allowed())
-                return;
+                return -ENODEV;
 
         printk(KERN_INFO  "Checking aperture...\n");
 
@@ -463,8 +463,9 @@ out:
                         unsigned long n = (32 * 1024 * 1024) << last_aper_order;
 
                         insert_aperture_resource((u32)last_aper_base, n);
+                        return 1;
                 }
-                return;
+                return 0;
         }
 
         if (!fallback_aper_force) {
@@ -500,7 +501,7 @@ out:
                         panic("Not enough memory for aperture");
                 }
         } else {
-                return;
+                return 0;
         }
 
         /* Fix up the north bridges */
@@ -526,4 +527,6 @@ out:
         }
 
         set_up_gart_resume(aper_order, aper_alloc);
+
+        return 1;
 }
diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 078d4ec1a9d9..f56a117cef68 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -47,6 +47,7 @@
 #include <asm/rio.h>
 #include <asm/bios_ebda.h>
 #include <asm/x86_init.h>
+#include <asm/iommu_table.h>
 
 #ifdef CONFIG_CALGARY_IOMMU_ENABLED_BY_DEFAULT
 int use_calgary __read_mostly = 1;
@@ -1364,7 +1365,7 @@ static int __init calgary_iommu_init(void)
         return 0;
 }
 
-void __init detect_calgary(void)
+int __init detect_calgary(void)
 {
         int bus;
         void *tbl;
@@ -1378,13 +1379,13 @@ void __init detect_calgary(void)
          * another HW IOMMU already, bail out.
          */
         if (no_iommu || iommu_detected)
-                return;
+                return -ENODEV;
 
         if (!use_calgary)
-                return;
+                return -ENODEV;
 
         if (!early_pci_allowed())
-                return;
+                return -ENODEV;
 
         printk(KERN_DEBUG "Calgary: detecting Calgary via BIOS EBDA area\n");
 
@@ -1410,13 +1411,13 @@ void __init detect_calgary(void)
         if (!rio_table_hdr) {
                 printk(KERN_DEBUG "Calgary: Unable to locate Rio Grande table "
                        "in EBDA - bailing!\n");
-                return;
+                return -ENODEV;
         }
 
         ret = build_detail_arrays();
         if (ret) {
                 printk(KERN_DEBUG "Calgary: build_detail_arrays ret %d\n", ret);
-                return;
+                return -ENOMEM;
         }
 
         specified_table_size = determine_tce_table_size((is_kdump_kernel() ?
@@ -1464,7 +1465,7 @@ void __init detect_calgary(void)
 
                 x86_init.iommu.iommu_init = calgary_iommu_init;
         }
-        return;
+        return calgary_found;
 
 cleanup:
         for (--bus; bus >= 0; --bus) {
@@ -1473,6 +1474,7 @@ cleanup:
                 if (info->tce_space)
                         free_tce_table(info->tce_space);
         }
+        return -ENOMEM;
 }
 
 static int __init calgary_parse_options(char *p)
@@ -1594,3 +1596,5 @@ static int __init calgary_fixup_tce_spaces(void)
  * and before device_initcall.
  */
 rootfs_initcall(calgary_fixup_tce_spaces);
+
+IOMMU_INIT_POST(detect_calgary);
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 9f07cfcbd3a5..9ea999a4dcc1 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -11,9 +11,8 @@
 #include <asm/iommu.h>
 #include <asm/gart.h>
 #include <asm/calgary.h>
-#include <asm/amd_iommu.h>
 #include <asm/x86_init.h>
-#include <asm/xen/swiotlb-xen.h>
+#include <asm/iommu_table.h>
 
 static int forbid_dac __read_mostly;
 
@@ -45,6 +44,8 @@ int iommu_detected __read_mostly = 0;
  */
 int iommu_pass_through __read_mostly;
 
+extern struct iommu_table_entry __iommu_table[], __iommu_table_end[];
+
 /* Dummy device used for NULL arguments (normally ISA). */
 struct device x86_dma_fallback_dev = {
         .init_name = "fallback device",
@@ -130,26 +131,24 @@ static void __init dma32_free_bootmem(void)
 
 void __init pci_iommu_alloc(void)
 {
+        struct iommu_table_entry *p;
+
         /* free the range so iommu could get some range less than 4G */
         dma32_free_bootmem();
 
-        if (pci_xen_swiotlb_detect() || pci_swiotlb_detect())
-                goto out;
-
-        gart_iommu_hole_init();
-
-        detect_calgary();
-
-        detect_intel_iommu();
+        sort_iommu_table(__iommu_table, __iommu_table_end);
+        check_iommu_entries(__iommu_table, __iommu_table_end);
 
-        /* needs to be called after gart_iommu_hole_init */
-        amd_iommu_detect();
-out:
-        pci_xen_swiotlb_init();
-
-        pci_swiotlb_init();
+        for (p = __iommu_table; p < __iommu_table_end; p++) {
+                if (p && p->detect && p->detect() > 0) {
+                        p->flags |= IOMMU_DETECTED;
+                        if (p->early_init)
+                                p->early_init();
+                        if (p->flags & IOMMU_FINISH_IF_DETECTED)
+                                break;
+                }
+        }
 }
-
 void *dma_generic_alloc_coherent(struct device *dev, size_t size,
                                  dma_addr_t *dma_addr, gfp_t flag)
 {
@@ -292,6 +291,7 @@ EXPORT_SYMBOL(dma_supported);
 
 static int __init pci_iommu_init(void)
 {
+        struct iommu_table_entry *p;
         dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
 
 #ifdef CONFIG_PCI
@@ -299,12 +299,10 @@ static int __init pci_iommu_init(void)
 #endif
         x86_init.iommu.iommu_init();
 
-        if (swiotlb || xen_swiotlb) {
-                printk(KERN_INFO "PCI-DMA: "
-                       "Using software bounce buffering for IO (SWIOTLB)\n");
-                swiotlb_print_info();
-        } else
-                swiotlb_free();
+        for (p = __iommu_table; p < __iommu_table_end; p++) {
+                if (p && (p->flags & IOMMU_DETECTED) && p->late_init)
+                        p->late_init();
+        }
 
         return 0;
 }
diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index c562207b1b3d..ba0f0ca9f280 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -41,6 +41,7 @@
 #include <asm/dma.h>
 #include <asm/amd_nb.h>
 #include <asm/x86_init.h>
+#include <asm/iommu_table.h>
 
 static unsigned long iommu_bus_base;    /* GART remapping area (physical) */
 static unsigned long iommu_size;        /* size of remapping area bytes */
@@ -905,3 +906,4 @@ void __init gart_parse_options(char *p)
                 }
         }
 }
+IOMMU_INIT_POST(gart_iommu_hole_init);
diff --git a/arch/x86/kernel/pci-iommu_table.c b/arch/x86/kernel/pci-iommu_table.c
new file mode 100644
index 000000000000..55d745ec1181
--- /dev/null
+++ b/arch/x86/kernel/pci-iommu_table.c
@@ -0,0 +1,89 @@
+#include <linux/dma-mapping.h>
+#include <asm/iommu_table.h>
+#include <linux/string.h>
+#include <linux/kallsyms.h>
+
+
+#define DEBUG 1
+
+static struct iommu_table_entry * __init
+find_dependents_of(struct iommu_table_entry *start,
+                   struct iommu_table_entry *finish,
+                   struct iommu_table_entry *q)
+{
+        struct iommu_table_entry *p;
+
+        if (!q)
+                return NULL;
+
+        for (p = start; p < finish; p++)
+                if (p->detect == q->depend)
+                        return p;
+
+        return NULL;
+}
+
+
+void __init sort_iommu_table(struct iommu_table_entry *start,
+                             struct iommu_table_entry *finish) {
+
+        struct iommu_table_entry *p, *q, tmp;
+
+        for (p = start; p < finish; p++) {
+again:
+                q = find_dependents_of(start, finish, p);
+                /* We are bit sneaky here. We use the memory address to figure
+                 * out if the node we depend on is past our point, if so, swap.
+                 */
+                if (q > p) {
+                        tmp = *p;
+                        memmove(p, q, sizeof(*p));
+                        *q = tmp;
+                        goto again;
+                }
+        }
+
+}
+
+#ifdef DEBUG
+void __init check_iommu_entries(struct iommu_table_entry *start,
+                                struct iommu_table_entry *finish)
+{
+        struct iommu_table_entry *p, *q, *x;
+        char sym_p[KSYM_SYMBOL_LEN];
+        char sym_q[KSYM_SYMBOL_LEN];
+
+        /* Simple cyclic dependency checker. */
+        for (p = start; p < finish; p++) {
+                q = find_dependents_of(start, finish, p);
+                x = find_dependents_of(start, finish, q);
+                if (p == x) {
+                        sprint_symbol(sym_p, (unsigned long)p->detect);
+                        sprint_symbol(sym_q, (unsigned long)q->detect);
+
+                        printk(KERN_ERR "CYCLIC DEPENDENCY FOUND! %s depends" \
+                                        " on %s and vice-versa. BREAKING IT.\n",
+                                        sym_p, sym_q);
+                        /* Heavy handed way..*/
+                        x->depend = 0;
+                }
+        }
+
+        for (p = start; p < finish; p++) {
+                q = find_dependents_of(p, finish, p);
+                if (q && q > p) {
+                        sprint_symbol(sym_p, (unsigned long)p->detect);
+                        sprint_symbol(sym_q, (unsigned long)q->detect);
+
+                        printk(KERN_ERR "EXECUTION ORDER INVALID! %s "\
+                                        "should be called before %s!\n",
+                                        sym_p, sym_q);
+                }
+        }
+}
+#else
+inline void check_iommu_entries(struct iommu_table_entry *start,
+                                       struct iommu_table_entry *finish)
+{
+}
+#endif
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index a5bc528d4328..8f972cbddef0 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -10,7 +10,8 @@
 #include <asm/iommu.h>
 #include <asm/swiotlb.h>
 #include <asm/dma.h>
-
+#include <asm/xen/swiotlb-xen.h>
+#include <asm/iommu_table.h>
 int swiotlb __read_mostly;
 
 static void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
@@ -41,25 +42,42 @@ static struct dma_map_ops swiotlb_dma_ops = {
 };
 
 /*
- * pci_swiotlb_detect - set swiotlb to 1 if necessary
+ * pci_swiotlb_detect_override - set swiotlb to 1 if necessary
  *
  * This returns non-zero if we are forced to use swiotlb (by the boot
  * option).
  */
-int __init pci_swiotlb_detect(void)
+int __init pci_swiotlb_detect_override(void)
 {
         int use_swiotlb = swiotlb | swiotlb_force;
 
+        if (swiotlb_force)
+                swiotlb = 1;
+
+        return use_swiotlb;
+}
+IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
+                  pci_xen_swiotlb_detect,
+                  pci_swiotlb_init,
+                  pci_swiotlb_late_init);
+
+/*
+ * if 4GB or more detected (and iommu=off not set) return 1
+ * and set swiotlb to 1.
+ */
+int __init pci_swiotlb_detect_4gb(void)
+{
         /* don't initialize swiotlb if iommu=off (no_iommu=1) */
 #ifdef CONFIG_X86_64
         if (!no_iommu && max_pfn > MAX_DMA32_PFN)
                 swiotlb = 1;
 #endif
-        if (swiotlb_force)
-                swiotlb = 1;
-
-        return use_swiotlb;
+        return swiotlb;
 }
+IOMMU_INIT(pci_swiotlb_detect_4gb,
+           pci_swiotlb_detect_override,
+           pci_swiotlb_init,
+           pci_swiotlb_late_init);
 
 void __init pci_swiotlb_init(void)
 {
@@ -68,3 +86,15 @@ void __init pci_swiotlb_init(void)
                 dma_ops = &swiotlb_dma_ops;
         }
 }
+
+void __init pci_swiotlb_late_init(void)
+{
+        /* An IOMMU turned us off. */
+        if (!swiotlb)
+                swiotlb_free();
+        else {
+                printk(KERN_INFO "PCI-DMA: "
+                       "Using software bounce buffering for IO (SWIOTLB)\n");
+                swiotlb_print_info();
+        }
+}
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index d0bb52296fa3..38e2b67807e1 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -242,6 +242,12 @@ SECTIONS
                 __x86_cpu_dev_end = .;
         }
 
+        /*
+         * start address and size of operations which during runtime
+         * can be patched with virtualization friendly instructions or
+         * baremetal native ones. Think page table operations.
+         * Details in paravirt_types.h
+         */
         . = ALIGN(8);
         .parainstructions : AT(ADDR(.parainstructions) - LOAD_OFFSET) {
                 __parainstructions = .;
@@ -249,6 +255,11 @@ SECTIONS
                 __parainstructions_end = .;
         }
 
+        /*
+         * struct alt_inst entries. From the header (alternative.h):
+         * "Alternative instructions for different CPU types or capabilities"
+         * Think locking instructions on spinlocks.
+         */
         . = ALIGN(8);
         .altinstructions : AT(ADDR(.altinstructions) - LOAD_OFFSET) {
                 __alt_instructions = .;
@@ -256,11 +267,28 @@ SECTIONS
                 __alt_instructions_end = .;
         }
 
+        /*
+         * And here are the replacement instructions. The linker sticks
+         * them as binary blobs. The .altinstructions has enough data to
+         * get the address and the length of them to patch the kernel safely.
+         */
         .altinstr_replacement : AT(ADDR(.altinstr_replacement) - LOAD_OFFSET) {
                 *(.altinstr_replacement)
         }
 
         /*
+         * struct iommu_table_entry entries are injected in this section.
+         * It is an array of IOMMUs which during run time gets sorted depending
+         * on its dependency order. After rootfs_initcall is complete
+         * this section can be safely removed.
+         */
+        .iommu_table : AT(ADDR(.iommu_table) - LOAD_OFFSET) {
+                __iommu_table = .;
+                *(.iommu_table)
+                __iommu_table_end = .;
+        }
+        . = ALIGN(8);
+        /*
          * .exit.text is discard at runtime, not link time, to deal with
          *  references from .altinstructions and .eh_frame
          */
diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index a013ec9d0c54..22471001b74c 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/arch/x86/xen/pci-swiotlb-xen.c
@@ -5,6 +5,7 @@
 
 #include <asm/xen/hypervisor.h>
 #include <xen/xen.h>
+#include <asm/iommu_table.h>
 
 int xen_swiotlb __read_mostly;
 
@@ -56,3 +57,7 @@ void __init pci_xen_swiotlb_init(void)
                 dma_ops = &xen_swiotlb_dma_ops;
         }
 }
+IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
+                  0,
+                  pci_xen_swiotlb_init,
+                  0);
diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 3de3a436a432..0157708d474d 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -36,6 +36,7 @@
 #include <linux/tboot.h>
 #include <linux/dmi.h>
 #include <linux/slab.h>
+#include <asm/iommu_table.h>
 
 #define PREFIX "DMAR: "
 
@@ -687,7 +688,7 @@ failed:
         return 0;
 }
 
-void __init detect_intel_iommu(void)
+int __init detect_intel_iommu(void)
 {
         int ret;
 
@@ -723,6 +724,8 @@ void __init detect_intel_iommu(void)
         }
         early_acpi_os_unmap_memory(dmar_tbl, dmar_tbl_size);
         dmar_tbl = NULL;
+
+        return ret ? 1 : -ENODEV;
 }
 
 
@@ -1455,3 +1458,4 @@ int __init dmar_ir_support(void)
                 return 0;
         return dmar->flags & 0x1;
 }
+IOMMU_INIT_POST(detect_intel_iommu);
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index 51651b76d40f..a7d9dc21391d 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -57,15 +57,15 @@ extern int dmar_table_init(void);
 extern int dmar_dev_scope_init(void);
 
 /* Intel IOMMU detection */
-extern void detect_intel_iommu(void);
+extern int detect_intel_iommu(void);
 extern int enable_drhd_fault_handling(void);
 
 extern int parse_ioapics_under_ir(void);
 extern int alloc_iommu(struct dmar_drhd_unit *);
 #else
-static inline void detect_intel_iommu(void)
+static inline int detect_intel_iommu(void)
 {
-        return;
+        return -ENODEV;
 }
 
 static inline int dmar_table_init(void)