This patch adds support for getting and using a local copy of the dirty
bitmap.
memory_region_snapshot_and_clear_dirty() will create a snapshot of the
dirty bitmap for the specified range, clear the dirty bitmap and return
the copy. The returned bitmap can be a bit larger than requested, the
range is expanded so the code can copy unsigned longs from the bitmap
and avoid atomic bit update operations.
memory_region_snapshot_get_dirty() will return the dirty status of
pages, pretty much like memory_region_get_dirty(), but using the copy
returned by memory_region_copy_and_clear_dirty().
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
include/exec/memory.h | 47 +++++++++++++++++++++++++++++++
include/exec/ram_addr.h | 7 +++++
include/qemu/typedefs.h | 1 +
exec.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++
memory.c | 17 +++++++++++
5 files changed, 147 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index f20b191793..1e15e79d00 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -871,6 +871,53 @@ void memory_region_set_dirty(MemoryRegion *mr, hwaddr addr,
*/
bool memory_region_test_and_clear_dirty(MemoryRegion *mr, hwaddr addr,
hwaddr size, unsigned client);
+
+/**
+ * memory_region_snapshot_and_clear_dirty: Get a snapshot of the dirty
+ * bitmap and clear it.
+ *
+ * Creates a snapshot of the dirty bitmap, clears the dirty bitmap and
+ * returns the snapshot. The snapshot can then be used to query dirty
+ * status, using memory_region_snapshot_get_dirty. Unlike
+ * memory_region_test_and_clear_dirty this allows to query the same
+ * page multiple times, which is especially useful for display updates
+ * where the scanlines often are not page aligned.
+ *
+ * The dirty bitmap region which gets copyed into the snapshot (and
+ * cleared afterwards) can be larger than requested. The boundaries
+ * are rounded up/down so complete bitmap longs (covering 64 pages on
+ * 64bit hosts) can be copied over into the bitmap snapshot. Which
+ * isn't a problem for display updates as the extra pages are outside
+ * the visible area, and in case the visible area changes a full
+ * display redraw is due anyway. Should other use cases for this
+ * function emerge we might have to revisit this implementation
+ * detail.
+ *
+ * Use g_free to release DirtyBitmapSnapshot.
+ *
+ * @mr: the memory region being queried.
+ * @addr: the address (relative to the start of the region) being queried.
+ * @size: the size of the range being queried.
+ * @client: the user of the logging information; typically %DIRTY_MEMORY_VGA.
+ */
+DirtyBitmapSnapshot *memory_region_snapshot_and_clear_dirty(MemoryRegion *mr,
+ hwaddr addr,
+ hwaddr size,
+ unsigned client);
+
+/**
+ * memory_region_snapshot_get_dirty: Check whether a range of bytes is dirty
+ * in the specified dirty bitmap snapshot.
+ *
+ * @mr: the memory region being queried.
+ * @snap: the dirty bitmap snapshot
+ * @addr: the address (relative to the start of the region) being queried.
+ * @size: the size of the range being queried.
+ */
+bool memory_region_snapshot_get_dirty(MemoryRegion *mr,
+ DirtyBitmapSnapshot *snap,
+ hwaddr addr, hwaddr size);
+
/**
* memory_region_sync_dirty_bitmap: Synchronize a region's dirty bitmap with
* any external TLBs (e.g. kvm)
diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index b05dc84ab9..2b63d7f59e 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -343,6 +343,13 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t
start,
ram_addr_t length,
unsigned client);
+DirtyBitmapSnapshot *cpu_physical_memory_snapshot_and_clear_dirty
+ (ram_addr_t start, ram_addr_t length, unsigned client);
+
+bool cpu_physical_memory_snapshot_get_dirty(DirtyBitmapSnapshot *snap,
+ ram_addr_t start,
+ ram_addr_t length);
+
static inline void cpu_physical_memory_clear_dirty_range(ram_addr_t start,
ram_addr_t length)
{
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index e95f28cfec..f08d327aec 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -23,6 +23,7 @@ typedef struct CPUAddressSpace CPUAddressSpace;
typedef struct CPUState CPUState;
typedef struct DeviceListener DeviceListener;
typedef struct DeviceState DeviceState;
+typedef struct DirtyBitmapSnapshot DirtyBitmapSnapshot;
typedef struct DisplayChangeListener DisplayChangeListener;
typedef struct DisplayState DisplayState;
typedef struct DisplaySurface DisplaySurface;
diff --git a/exec.c b/exec.c
index c97ef4a8da..a8894d5ba2 100644
--- a/exec.c
+++ b/exec.c
@@ -223,6 +223,12 @@ struct CPUAddressSpace {
MemoryListener tcg_as_listener;
};
+struct DirtyBitmapSnapshot {
+ ram_addr_t start;
+ ram_addr_t end;
+ unsigned long dirty[];
+};
+
#endif
#if !defined(CONFIG_USER_ONLY)
@@ -1061,6 +1067,75 @@ bool cpu_physical_memory_test_and_clear_dirty(ram_addr_t
start,
return dirty;
}
+DirtyBitmapSnapshot *cpu_physical_memory_snapshot_and_clear_dirty
+ (ram_addr_t start, ram_addr_t length, unsigned client)
+{
+ DirtyMemoryBlocks *blocks;
+ unsigned long align = 1UL << (TARGET_PAGE_BITS + BITS_PER_LEVEL);
+ ram_addr_t first = QEMU_ALIGN_DOWN(start, align);
+ ram_addr_t last = QEMU_ALIGN_UP(start + length, align);
+ DirtyBitmapSnapshot *snap;
+ unsigned long page, end, dest;
+
+ snap = g_malloc0(sizeof(*snap) +
+ ((last - first) >> (TARGET_PAGE_BITS + 3)));
+ snap->start = first;
+ snap->end = last;
+
+ page = first >> TARGET_PAGE_BITS;
+ end = last >> TARGET_PAGE_BITS;
+ dest = 0;
+
+ rcu_read_lock();
+
+ blocks = atomic_rcu_read(&ram_list.dirty_memory[client]);
+
+ while (page < end) {
+ unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
+ unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
+ unsigned long num = MIN(end - page, DIRTY_MEMORY_BLOCK_SIZE - offset);
+
+ assert(QEMU_IS_ALIGNED(offset, (1 << BITS_PER_LEVEL)));
+ assert(QEMU_IS_ALIGNED(num, (1 << BITS_PER_LEVEL)));
+ offset >>= BITS_PER_LEVEL;
+
+ bitmap_copy_and_clear_atomic(snap->dirty + dest,
+ blocks->blocks[idx] + offset,
+ num);
+ page += num;
+ dest += num >> BITS_PER_LEVEL;
+ }
+
+ rcu_read_unlock();
+
+ if (tcg_enabled()) {
+ tlb_reset_dirty_range_all(start, length);
+ }
+
+ return snap;
+}
+
+bool cpu_physical_memory_snapshot_get_dirty(DirtyBitmapSnapshot *snap,
+ ram_addr_t start,
+ ram_addr_t length)
+{
+ unsigned long page, end;
+
+ assert(start >= snap->start);
+ assert(start + length <= snap->end);
+
+ end = TARGET_PAGE_ALIGN(start + length - snap->start) >> TARGET_PAGE_BITS;
+ page = (start - snap->start) >> TARGET_PAGE_BITS;
+
+ while (page < end) {
+ if (test_bit(page, snap->dirty)) {
+ return true;
+ }
+ page++;
+ }
+ return false;
+}
+
/* Called from RCU critical section */
hwaddr memory_region_section_get_iotlb(CPUState *cpu,
MemoryRegionSection *section,
diff --git a/memory.c b/memory.c
index 4c95aaf39c..8a0648551f 100644
--- a/memory.c
+++ b/memory.c
@@ -1716,6 +1716,23 @@ bool memory_region_test_and_clear_dirty(MemoryRegion
*mr, hwaddr addr,
memory_region_get_ram_addr(mr) + addr, size, client);
}
+DirtyBitmapSnapshot *memory_region_snapshot_and_clear_dirty(MemoryRegion *mr,
+ hwaddr addr,
+ hwaddr size,
+ unsigned client)
+{
+ assert(mr->ram_block);
+ return cpu_physical_memory_snapshot_and_clear_dirty(
+ memory_region_get_ram_addr(mr) + addr, size, client);
+}
+
+bool memory_region_snapshot_get_dirty(MemoryRegion *mr, DirtyBitmapSnapshot
*snap,
+ hwaddr addr, hwaddr size)
+{
+ assert(mr->ram_block);
+ return cpu_physical_memory_snapshot_get_dirty(snap,
+ memory_region_get_ram_addr(mr) + addr, size);
+}
void memory_region_sync_dirty_bitmap(MemoryRegion *mr)
{
--
2.9.3
