[Xen-changelog] [xen master] libxl: allow copying between bitmaps of different sizes

[patchbot@xxxxxxx]

commit 1c098487d36f2ab1d698a2b163d9d692facaf2ac
Author:     Wei Liu <wei.liu2@xxxxxxxxxx>
AuthorDate: Tue Nov 25 10:59:47 2014 +0000
Commit:     Ian Campbell <ian.campbell@xxxxxxxxxx>
CommitDate: Fri Nov 28 11:01:00 2014 +0000

    libxl: allow copying between bitmaps of different sizes
    
    When parsing bitmap objects JSON parser will create libxl_bitmap map of the
    smallest size needed.
    
    This can cause problems when saved image file specifies CPU affinity.  For
    example, if 'vcpu_hard_affinity' in the saved image has only the first CPU
    specified, just a single byte will be allocated and libxl_bitmap->size will 
be
    set to 1.
    
    This will result in assertion in 
libxl_set_vcpuaffinity()->libxl_bitmap_copy()
    since the destination bitmap is created for maximum number of CPUs.
    
    We could allocate that bitmap of the same size as the source, however, it is
    later passed to xc_vcpu_setaffinity() which expects it to be sized to the 
max
    number of CPUs
    
    To fix this issue, introduce an internal function to allowing copying 
between
    bitmaps of different sizes. Note that this function is only used in
    libxl_set_vcpuaffinity at the moment. Though NUMA placement logic invoke
    libxl_bitmap_copy as well there's no need to replace those invocations.  
NUMA
    placement logic comes into effect when no vcpu / node pinning is provided, 
so
    it always operates on bitmap of the same sizes (that is, size of maximum
    number of cpus /nodes).
    
    Reported-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
    Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
    Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Cc: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
    Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
    Tested-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
    Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 tools/libxl/libxl.c          |    4 ++--
 tools/libxl/libxl_internal.h |   11 +++++++++++
 tools/libxl/libxl_utils.c    |   15 +++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index de23fec..1e9da10 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -5320,7 +5320,7 @@ int libxl_set_vcpuaffinity(libxl_ctx *ctx, uint32_t 
domid, uint32_t vcpuid,
         if (rc)
             goto out;
 
-        libxl_bitmap_copy(ctx, &hard, cpumap_hard);
+        libxl__bitmap_copy_best_effort(gc, &hard, cpumap_hard);
         flags = XEN_VCPUAFFINITY_HARD;
     }
     if (cpumap_soft) {
@@ -5328,7 +5328,7 @@ int libxl_set_vcpuaffinity(libxl_ctx *ctx, uint32_t 
domid, uint32_t vcpuid,
         if (rc)
             goto out;
 
-        libxl_bitmap_copy(ctx, &soft, cpumap_soft);
+        libxl__bitmap_copy_best_effort(gc, &soft, cpumap_soft);
         flags |= XEN_VCPUAFFINITY_SOFT;
     }
 
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 4361421..a38f695 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3617,6 +3617,17 @@ static inline void libxl__update_config_vtpm(libxl__gc 
*gc,
         libxl_device_##type##_copy(CTX, DA_p, (dev));           \
     })
 
+/* This function copies X bytes from source to destination bitmap,
+ * where X is the smaller of the two sizes.
+ *
+ * If destination's size is larger than source, the extra bytes are
+ * untouched.
+ *
+ * XXX This is introduced to fix a regression for 4.5. It shall
+ * be revisited in 4.6 time frame.
+ */
+void libxl__bitmap_copy_best_effort(libxl__gc *gc, libxl_bitmap *dptr,
+                                    const libxl_bitmap *sptr);
 #endif
 
 /*
diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c
index 58df4f3..3e1ba17 100644
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -614,6 +614,21 @@ void libxl_bitmap_copy(libxl_ctx *ctx, libxl_bitmap *dptr,
     memcpy(dptr->map, sptr->map, sz * sizeof(*dptr->map));
 }
 
+/* This function copies X bytes from source to destination bitmap,
+ * where X is the smaller of the two sizes.
+ *
+ * If destination's size is larger than source, the extra bytes are
+ * untouched.
+ */
+void libxl__bitmap_copy_best_effort(libxl__gc *gc, libxl_bitmap *dptr,
+                                    const libxl_bitmap *sptr)
+{
+    int sz;
+
+    sz = dptr->size < sptr->size ? dptr->size : sptr->size;
+    memcpy(dptr->map, sptr->map, sz * sizeof(*dptr->map));
+}
+
 void libxl_bitmap_copy_alloc(libxl_ctx *ctx,
                              libxl_bitmap *dptr,
                              const libxl_bitmap *sptr)
--
generated by git-patchbot for /home/xen/git/xen.git#master

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog