Most of the time, not all bitmaps have to be marked as dirty;
do not do anything if the interesting ones are already dirty.
Previously, any clean bitmap would have cause all the bitmaps to be
marked dirty.
In fact, unless running TCG most of the time bitmap operations need
not be done at all, because memory_region_is_logging returns zero.
In this case, skip the call to cpu_physical_memory_range_includes_clean
altogether as well.
With this patch, cpu_physical_memory_set_dirty_range is called
unconditionally, so there need not be anymore a separate call to
xen_modified_memory.
Backports commit e87f7778b64d4a6a78e16c288c7fdc6c15317d5f from qemu
cpu_physical_memory_set_dirty_lebitmap unconditionally syncs the
DIRTY_MEMORY_CODE bitmap. This however is unused unless TCG is
enabled.
Backports commit 9460dee4b2258e3990906fb34099481c8334c267 from qemu
While it is obvious that cpu_physical_memory_get_dirty returns true even if
a single page is dirty, the same is not true for cpu_physical_memory_get_clean;
one would expect that it returns true only if all the pages are clean, but
it actually looks for even one clean page. (By contrast, the caller of that
function, cpu_physical_memory_range_includes_clean, has a good name).
To clarify, rename the function to cpu_physical_memory_all_dirty and return
true if _all_ the pages are dirty. This is the opposite of the previous
meaning, because "all are 1" is the same as "not (any is 0)", so we have to
modify cpu_physical_memory_range_includes_clean as well
Backports commit 72b47e79cef36ed6ffc718f10e21001d7ec2a66f from qemu
