[Xen-devel] [PATCH 1/2][PVFB][TOOLS] PVFB frontend can send bogus screen updates

[Markus Armbruster <armbru@xxxxxxxxxx>]

The PVFB frontend can get confused and send a screen update to the
backend when the screen is actually clean.  Such an update asks for
the impossible rectangle (x1, x2, y1, y2) = (INT_MAX, 0, INT_MAX, 0).
Fix by setting the dirty flag in the obvious place: when the dirty
rectangle is grown.

Signed-off-by: Markus Armbruster <armbru@xxxxxxxxxx>

diff -r cf8b6cafa2f0 drivers/xen/fbfront/xenfb.c
--- a/drivers/xen/fbfront/xenfb.c       Thu Nov 08 18:26:08 2007 +0000
+++ b/drivers/xen/fbfront/xenfb.c       Tue Nov 13 17:32:48 2007 +0100
@@ -201,6 +201,11 @@ static void xenfb_update_screen(struct x
 
        mutex_unlock(&info->mm_lock);
 
+       if (x2 < x1 || y2 < y1) {
+               printk("xenfb_update_screen bogus rect %d %d %d %d\n",
+                      x1, x2, y1, y2);
+               WARN_ON(1);
+       }
        xenfb_do_update(info, x1, y1, x2 - x1, y2 - y1);
 }
 
@@ -252,7 +257,6 @@ static void xenfb_timer(unsigned long da
 static void xenfb_timer(unsigned long data)
 {
        struct xenfb_info *info = (struct xenfb_info *)data;
-       info->dirty = 1;
        wake_up(&info->wq);
 }
 
@@ -272,6 +276,7 @@ static void __xenfb_refresh(struct xenfb
                info->x1 = x1;
        if (info->x2 < x2)
                info->x2 = x2;
+       info->dirty = 1;
 
        if (timer_pending(&info->refresh))
                return;

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