1 files changed, 34 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 95edad4faf26..c08ceca6277d 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -47,6 +47,8 @@ static int novmerge = 0;
 static int novmerge = 1;
 #endif
 
+static int protect4gb = 1;
+
 static inline unsigned long iommu_num_pages(unsigned long vaddr,
 					    unsigned long slen)
 {
@@ -58,6 +60,16 @@ static inline unsigned long iommu_num_pages(unsigned long vaddr,
 	return npages;
 }
 
+static int __init setup_protect4gb(char *str)
+{
+	if (strcmp(str, "on") == 0)
+		protect4gb = 1;
+	else if (strcmp(str, "off") == 0)
+		protect4gb = 0;
+
+	return 1;
+}
+
 static int __init setup_iommu(char *str)
 {
 	if (!strcmp(str, "novmerge"))
@@ -67,6 +79,7 @@ static int __init setup_iommu(char *str)
 	return 1;
 }
 
+__setup("protect4gb=", setup_protect4gb);
 __setup("iommu=", setup_iommu);
 
 static unsigned long iommu_range_alloc(struct iommu_table *tbl,
@@ -429,6 +442,9 @@ void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist,
 struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
 {
 	unsigned long sz;
+	unsigned long start_index, end_index;
+	unsigned long entries_per_4g;
+	unsigned long index;
 	static int welcomed = 0;
 	struct page *page;
 
@@ -450,7 +466,7 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
 
 #ifdef CONFIG_CRASH_DUMP
 	if (ppc_md.tce_get) {
-		unsigned long index, tceval;
+		unsigned long tceval;
 		unsigned long tcecount = 0;
 
 		/*
@@ -480,6 +496,23 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid)
 	ppc_md.tce_free(tbl, tbl->it_offset, tbl->it_size);
 #endif
 
+	/*
+	 * DMA cannot cross 4 GB boundary.  Mark last entry of each 4
+	 * GB chunk as reserved.
+	 */
+	if (protect4gb) {
+		entries_per_4g = 0x100000000l >> IOMMU_PAGE_SHIFT;
+
+		/* Mark the last bit before a 4GB boundary as used */
+		start_index = tbl->it_offset | (entries_per_4g - 1);
+		start_index -= tbl->it_offset;
+
+		end_index = tbl->it_size;
+
+		for (index = start_index; index < end_index - 1; index += entries_per_4g)
+			__set_bit(index, tbl->it_map);
+	}
+
 	if (!welcomed) {
 		printk(KERN_INFO "IOMMU table initialized, virtual merging %s\n",
 		       novmerge ? "disabled" : "enabled");