swiotlb: don't assume PA 0 is invalid

In 2.6.29 io_tlb_orig_addr[] got converted from storing virtual addresses
to storing physical ones. While checking virtual addresses against NULL
is a legitimate thing to catch invalid entries, checking physical ones
against zero isn't: There's no guarantee that PFN 0 is reserved on a
particular platform.

Since it is unclear whether the check in swiotlb_tbl_unmap_single() is
actually needed, retain it but check against a guaranteed invalid physical
address. This requires setting up the array in a suitable fashion. And
since the original code failed to invalidate array entries when regions
get unmapped, this is being fixed at once along with adding a similar
check to swiotlb_tbl_sync_single().

Obviously the less intrusive change would be to simply drop the check in
swiotlb_tbl_unmap_single().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 649d097853a1..4abda074ea45 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -86,6 +86,7 @@ static unsigned int io_tlb_index;
  * We need to save away the original address corresponding to a mapped entry
  * for the sync operations.
  */
+#define INVALID_PHYS_ADDR (~(phys_addr_t)0)
 static phys_addr_t *io_tlb_orig_addr;
 
 /*
@@ -188,12 +189,14 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
         io_tlb_list = memblock_virt_alloc(
                                 PAGE_ALIGN(io_tlb_nslabs * sizeof(int)),
                                 PAGE_SIZE);
-        for (i = 0; i < io_tlb_nslabs; i++)
-                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
-        io_tlb_index = 0;
         io_tlb_orig_addr = memblock_virt_alloc(
                                 PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)),
                                 PAGE_SIZE);
+        for (i = 0; i < io_tlb_nslabs; i++) {
+                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+                io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+        }
+        io_tlb_index = 0;
 
         if (verbose)
                 swiotlb_print_info();
@@ -313,10 +316,6 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
         if (!io_tlb_list)
                 goto cleanup3;
 
-        for (i = 0; i < io_tlb_nslabs; i++)
-                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
-        io_tlb_index = 0;
-
         io_tlb_orig_addr = (phys_addr_t *)
                 __get_free_pages(GFP_KERNEL,
                                  get_order(io_tlb_nslabs *
@@ -324,7 +323,11 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
         if (!io_tlb_orig_addr)
                 goto cleanup4;
 
-        memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(phys_addr_t));
+        for (i = 0; i < io_tlb_nslabs; i++) {
+                io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+                io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+        }
+        io_tlb_index = 0;
 
         swiotlb_print_info();
 
@@ -556,7 +559,8 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
         /*
          * First, sync the memory before unmapping the entry
          */
-        if (orig_addr && ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
+        if (orig_addr != INVALID_PHYS_ADDR &&
+            ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL)))
                 swiotlb_bounce(orig_addr, tlb_addr, size, DMA_FROM_DEVICE);
 
         /*
@@ -573,8 +577,10 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
                  * Step 1: return the slots to the free list, merging the
                  * slots with superceeding slots
                  */
-                for (i = index + nslots - 1; i >= index; i--)
+                for (i = index + nslots - 1; i >= index; i--) {
                         io_tlb_list[i] = ++count;
+                        io_tlb_orig_addr[i] = INVALID_PHYS_ADDR;
+                }
                 /*
                  * Step 2: merge the returned slots with the preceding slots,
                  * if available (non zero)
@@ -593,6 +599,8 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
         int index = (tlb_addr - io_tlb_start) >> IO_TLB_SHIFT;
         phys_addr_t orig_addr = io_tlb_orig_addr[index];
 
+        if (orig_addr == INVALID_PHYS_ADDR)
+                return;
         orig_addr += (unsigned long)tlb_addr & ((1 << IO_TLB_SHIFT) - 1);
 
         switch (target) {