[Qemu-devel] [PATCH] cirrus: handle negative pitch in cirrus_invalidate_region()

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

cirrus_invalidate_region() calls memory_region_set_dirty()
on a per-line basis, always ranging from off_begin to
off_begin+bytesperline. With a negative pitch off_begin
marks the top most used address and thus we need to do an
initial shift backwards by bytesperline for negative
pitches of backward blits, otherwise the first iteration
covers the line going from the start offset forwards instead
of backwards.

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
---
I bumped the patch context to 4 lines to get it to include the
memory_region_set_dirty() call which takes an unsigned length (`hwaddr
size`) because I'm also not too happy about the masking going on there
since it means off_cur_end may be less than off_cur, but if the range
checks are finnaly correct I don't think this case could happen
anymore? (A check shouldn't hurt though, or maybe an assert()?)

 hw/display/cirrus_vga.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index b1a0773..af61981 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -669,8 +669,12 @@ static void cirrus_invalidate_region(CirrusVGAState * s, int off_begin,
     int y;
     int off_cur;
     int off_cur_end;
 
+    if (off_pitch < 0) {
+        off_begin -= bytesperline;
+    }
+
     for (y = 0; y < lines; y++) {
 	off_cur = off_begin;
 	off_cur_end = (off_cur + bytesperline) & s->cirrus_addr_mask;
         memory_region_set_dirty(&s->vga.vram, off_cur, off_cur_end - off_cur);
-- 
2.1.4