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memory: add support getting and using a dirty bitmap copy.

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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 <kraxel@redhat.com>
Message-id: 20170421091632.30900-3-kraxel@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Gerd Hoffmann 2017-04-21 11:16:25 +02:00
parent d6eb141392
commit 8deaf12ca1
5 changed files with 147 additions and 0 deletions
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47
include/exec/memory.h
View file

@ -918,6 +918,53 @@ 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)

7
include/exec/ram_addr.h
View file

@ -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)
{