4 files changed, 34 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d0dcaf35b429..115fa399608c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2290,15 +2290,6 @@ unlock:
         mutex_unlock(&obj->mm.lock);
 }
 
-static unsigned int swiotlb_max_size(void)
-{
-#if IS_ENABLED(CONFIG_SWIOTLB)
-        return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE);
-#else
-        return 0;
-#endif
-}
-
 static void i915_sg_trim(struct sg_table *orig_st)
 {
         struct sg_table new_st;
@@ -2345,7 +2336,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
         GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
         GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
 
-        max_segment = swiotlb_max_size();
+        max_segment = swiotlb_max_segment();
         if (!max_segment)
                 max_segment = rounddown(UINT_MAX, PAGE_SIZE);
 
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index aba12009422e..f905d6eeb048 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -275,6 +275,10 @@ retry:
                 rc = 0;
         } else
                 rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
+
+        if (!rc)
+                swiotlb_set_max_segment(PAGE_SIZE);
+
         return rc;
 error:
         if (repeat--) {
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index d9c84a9cde3d..4ee479f2f355 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -114,11 +114,14 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask);
 
 #ifdef CONFIG_SWIOTLB
 extern void __init swiotlb_free(void);
+unsigned int swiotlb_max_segment(void);
 #else
 static inline void swiotlb_free(void) { }
+static inline unsigned int swiotlb_max_segment(void) { return 0; }
 #endif
 
 extern void swiotlb_print_info(void);
 extern int is_swiotlb_buffer(phys_addr_t paddr);
+extern void swiotlb_set_max_segment(unsigned int);
 
 #endif /* __LINUX_SWIOTLB_H */
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 9def738af4f4..975b8fc4f1e1 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -83,6 +83,12 @@ static unsigned int *io_tlb_list;
 static unsigned int io_tlb_index;
 
 /*
+ * Max segment that we can provide which (if pages are contingous) will
+ * not be bounced (unless SWIOTLB_FORCE is set).
+ */
+unsigned int max_segment;
+
+/*
  * We need to save away the original address corresponding to a mapped entry
  * for the sync operations.
  */
@@ -124,6 +130,20 @@ unsigned long swiotlb_nr_tbl(void)
 }
 EXPORT_SYMBOL_GPL(swiotlb_nr_tbl);
 
+unsigned int swiotlb_max_segment(void)
+{
+        return max_segment;
+}
+EXPORT_SYMBOL_GPL(swiotlb_max_segment);
+
+void swiotlb_set_max_segment(unsigned int val)
+{
+        if (swiotlb_force == SWIOTLB_FORCE)
+                max_segment = 1;
+        else
+                max_segment = rounddown(val, PAGE_SIZE);
+}
+
 /* default to 64MB */
 #define IO_TLB_DEFAULT_SIZE (64UL<<20)
 unsigned long swiotlb_size_or_default(void)
@@ -205,6 +225,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
         if (verbose)
                 swiotlb_print_info();
 
+        swiotlb_set_max_segment(io_tlb_nslabs << IO_TLB_SHIFT);
         return 0;
 }
 
@@ -283,6 +304,7 @@ swiotlb_late_init_with_default_size(size_t default_size)
         rc = swiotlb_late_init_with_tbl(vstart, io_tlb_nslabs);
         if (rc)
                 free_pages((unsigned long)vstart, order);
+
         return rc;
 }
 
@@ -337,6 +359,8 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
 
         late_alloc = 1;
 
+        swiotlb_set_max_segment(io_tlb_nslabs << IO_TLB_SHIFT);
+
         return 0;
 
 cleanup4:
@@ -351,6 +375,7 @@ cleanup2:
         io_tlb_end = 0;
         io_tlb_start = 0;
         io_tlb_nslabs = 0;
+        max_segment = 0;
         return -ENOMEM;
 }
 
@@ -379,6 +404,7 @@ void __init swiotlb_free(void)
                                    PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
         }
         io_tlb_nslabs = 0;
+        max_segment = 0;
 }
 
 int is_swiotlb_buffer(phys_addr_t paddr)