v4.19.13 snapshot.
diff --git a/arch/x86/kernel/pci-iommu_table.c b/arch/x86/kernel/pci-iommu_table.c
new file mode 100644
index 0000000..2e9006c
--- /dev/null
+++ b/arch/x86/kernel/pci-iommu_table.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+#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;
+
+ /* 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) {
+ printk(KERN_ERR "CYCLIC DEPENDENCY FOUND! %pS depends on %pS and vice-versa. BREAKING IT.\n",
+ p->detect, q->detect);
+ /* Heavy handed way..*/
+ x->depend = NULL;
+ }
+ }
+
+ for (p = start; p < finish; p++) {
+ q = find_dependents_of(p, finish, p);
+ if (q && q > p) {
+ printk(KERN_ERR "EXECUTION ORDER INVALID! %pS should be called before %pS!\n",
+ p->detect, q->detect);
+ }
+ }
+}
+#else
+void __init check_iommu_entries(struct iommu_table_entry *start,
+ struct iommu_table_entry *finish)
+{
+}
+#endif