[PATCH v2 1/6] memory: Export a helper to get intersection of a MemoryRegionSection with a given range

[Chenyi Qiang <chenyi.qiang@xxxxxxxxx>]

Rename the helper to memory_region_section_intersect_range() to make it
more generic. Meanwhile, define the @end as Int128 and replace the
related operations with Int128_* format since the helper is exported as
a wider API.

Suggested-by: Alexey Kardashevskiy <aik@xxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx>
---
Changes in v2:
- Make memory_region_section_intersect_range() an inline function.
- Add Reviewed-by from David
- Define the @end as Int128 and use the related Int128_* ops as a wilder
  API (Alexey)
---
 hw/virtio/virtio-mem.c | 32 +++++---------------------------
 include/exec/memory.h  | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index b1a003736b..21f16e4912 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -244,28 +244,6 @@ static int virtio_mem_for_each_plugged_range(VirtIOMEM *vmem, void *arg,
     return ret;
 }
 
-/*
- * Adjust the memory section to cover the intersection with the given range.
- *
- * Returns false if the intersection is empty, otherwise returns true.
- */
-static bool virtio_mem_intersect_memory_section(MemoryRegionSection *s,
-                                                uint64_t offset, uint64_t size)
-{
-    uint64_t start = MAX(s->offset_within_region, offset);
-    uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
-                       offset + size);
-
-    if (end <= start) {
-        return false;
-    }
-
-    s->offset_within_address_space += start - s->offset_within_region;
-    s->offset_within_region = start;
-    s->size = int128_make64(end - start);
-    return true;
-}
-
 typedef int (*virtio_mem_section_cb)(MemoryRegionSection *s, void *arg);
 
 static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
@@ -287,7 +265,7 @@ static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
                                       first_bit + 1) - 1;
         size = (last_bit - first_bit + 1) * vmem->block_size;
 
-        if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
+        if (!memory_region_section_intersect_range(&tmp, offset, size)) {
             break;
         }
         ret = cb(&tmp, arg);
@@ -319,7 +297,7 @@ static int virtio_mem_for_each_unplugged_section(const VirtIOMEM *vmem,
                                  first_bit + 1) - 1;
         size = (last_bit - first_bit + 1) * vmem->block_size;
 
-        if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
+        if (!memory_region_section_intersect_range(&tmp, offset, size)) {
             break;
         }
         ret = cb(&tmp, arg);
@@ -355,7 +333,7 @@ static void virtio_mem_notify_unplug(VirtIOMEM *vmem, uint64_t offset,
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         MemoryRegionSection tmp = *rdl->section;
 
-        if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
+        if (!memory_region_section_intersect_range(&tmp, offset, size)) {
             continue;
         }
         rdl->notify_discard(rdl, &tmp);
@@ -371,7 +349,7 @@ static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
     QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
         MemoryRegionSection tmp = *rdl->section;
 
-        if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
+        if (!memory_region_section_intersect_range(&tmp, offset, size)) {
             continue;
         }
         ret = rdl->notify_populate(rdl, &tmp);
@@ -388,7 +366,7 @@ static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
             if (rdl2 == rdl) {
                 break;
             }
-            if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
+            if (!memory_region_section_intersect_range(&tmp, offset, size)) {
                 continue;
             }
             rdl2->notify_discard(rdl2, &tmp);
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 3ee1901b52..3bebc43d59 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1202,6 +1202,33 @@ MemoryRegionSection *memory_region_section_new_copy(MemoryRegionSection *s);
  */
 void memory_region_section_free_copy(MemoryRegionSection *s);
 
+/**
+ * memory_region_section_intersect_range: Adjust the memory section to cover
+ * the intersection with the given range.
+ *
+ * @s: the #MemoryRegionSection to be adjusted
+ * @offset: the offset of the given range in the memory region
+ * @size: the size of the given range
+ *
+ * Returns false if the intersection is empty, otherwise returns true.
+ */
+static inline bool memory_region_section_intersect_range(MemoryRegionSection *s,
+                                                         uint64_t offset, uint64_t size)
+{
+    uint64_t start = MAX(s->offset_within_region, offset);
+    Int128 end = int128_min(int128_add(int128_make64(s->offset_within_region), s->size),
+                            int128_add(int128_make64(offset), int128_make64(size)));
+
+    if (int128_le(end, int128_make64(start))) {
+        return false;
+    }
+
+    s->offset_within_address_space += start - s->offset_within_region;
+    s->offset_within_region = start;
+    s->size = int128_sub(end, int128_make64(start));
+    return true;
+}
+
 /**
  * memory_region_init: Initialize a memory region
  *
-- 
2.43.5