[Xen-devel] [PATCH]: QEMU: Additional error checking in Cirrus setup

[Chris Lalancette <clalance@xxxxxxxxxx>]

All,
     Attached is a patch to do some additional error checking in QEMU when
setting up the Cirrus Logic video device.  In particular, it may be the case
that that set_mm_mapping() fails because of xc_domain_populate_physmap().  In
this case, we should not blindly go on; the xc_map_foreign_batch() that follows
will cause a page fault and, at best, get mapped in a zeroed page from the dom0
(which is not what we want).  While I'm in here, fix a memory leak on an error 
path.

The patch is against 3.1.0, but should apply fairly easily to xen-unstable.

Signed-off-by: Chris Lalancette <clalance@xxxxxxxxxx>

diff -urp xen-3.1.0-src.orig/tools/ioemu/hw/cirrus_vga.c 
xen-3.1.0-src/tools/ioemu/hw/cirrus_vga.c
--- xen-3.1.0-src.orig/tools/ioemu/hw/cirrus_vga.c      2007-05-18 
10:45:21.000000000 -0400
+++ xen-3.1.0-src/tools/ioemu/hw/cirrus_vga.c   2007-08-24 09:58:43.000000000 
-0400
@@ -2554,7 +2554,11 @@ static void *set_vram_mapping(unsigned l
     for (i = 0; i < nr_extents; i++)
         extent_start[i] = (begin + i * TARGET_PAGE_SIZE) >> TARGET_PAGE_BITS;
 
-    set_mm_mapping(xc_handle, domid, nr_extents, 0, extent_start);
+    if (set_mm_mapping(xc_handle, domid, nr_extents, 0, extent_start) < 0) {
+        fprintf(logfile, "Failed set_mm_mapping\n");
+        free(extent_start);
+        return NULL;
+    }
 
     vram_pointer = xc_map_foreign_batch(xc_handle, domid,
                                         PROT_READ|PROT_WRITE,
@@ -2562,6 +2566,7 @@ static void *set_vram_mapping(unsigned l
     if (vram_pointer == NULL) {
         fprintf(logfile, "xc_map_foreign_batch vgaram returned error %d\n",
                 errno);
+        free(extent_start);
         return NULL;
     }
 

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