cirrus: avoid resetting vga dirty logging unnecessarily (Avi Kivity)

cirrus bitblt reset will stop and start dirty logging even when there is no
need; this causes full redraws.

avoid by only updating memory access when exiting cpu-to-video update mode.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6384 c046a42c-6fe2-441c-8c8c-71466251a162

hw/cirrus_vga.c

@@ -850,11 +850,17 @@ static void cirrus_bitblt_cputovideo_next(CirrusVGAState * s)
 
 static void cirrus_bitblt_reset(CirrusVGAState * s)
 {
+    int need_update;
+
     s->gr[0x31] &=
 	~(CIRRUS_BLT_START | CIRRUS_BLT_BUSY | CIRRUS_BLT_FIFOUSED);
+    need_update = s->cirrus_srcptr != &s->cirrus_bltbuf[0]
+        || s->cirrus_srcptr_end != &s->cirrus_bltbuf[0];
     s->cirrus_srcptr = &s->cirrus_bltbuf[0];
     s->cirrus_srcptr_end = &s->cirrus_bltbuf[0];
     s->cirrus_srccounter = 0;
+    if (!need_update)
+        return;
     cirrus_update_memory_access(s);
 }