[PATCH] ati-vga: Do not allow unaligned access via index register

[BALATON Zoltan]

According to docs bits 1 and 0 of MM_INDEX are hard coded to 0 so
unaligned access via this register should not be possible.
This also fixes problems reported in bug #1878134.

Signed-off-by: BALATON Zoltan <bala...@eik.bme.hu>
---
 hw/display/ati.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index f4c4542751..2ee23173b2 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -531,7 +531,7 @@ static void ati_mm_write(void *opaque, hwaddr addr,
     }
     switch (addr) {
     case MM_INDEX:
-        s->regs.mm_index = data;
+        s->regs.mm_index = data & ~3;
         break;
     case MM_DATA ... MM_DATA + 3:
         /* indexed access to regs or memory */
-- 
2.21.3