[Xen-changelog] [xen stable-4.6] libxl: keep PoD target adjustment by memory fudge after reload_domain_config()

[patchbot@xxxxxxx]

commit 7c5c20d129b1a333a3f85a2d04ecde48b5fd7589
Author:     Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
AuthorDate: Wed Feb 3 16:53:03 2016 +0100
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Tue Jun 7 17:03:39 2016 +0100

    libxl: keep PoD target adjustment by memory fudge after 
reload_domain_config()
    
    Commit 56fb5fd623 ("libxl: adjust PoD target by memory fudge, too")
    introduced target_memkb adjustment for HVM PoD domains on create,
    wherein the value it wrote to target is always 1MiB lower than the
    actual target_memkb.  Unfortunately, on reboot, it is this value which
    is read *unmodified* to feed into the next domain creation; from which
    1MiB is subtracted *again*.  This means that any guest which reboots
    with memory < maxmem will have its memory target decreased by 1MiB on
    every boot.
    
    This patch makes it so that when reading target on reboot, we adjust the
    value we read *up* by 1MiB, so that the domain will be build with the
    appropriate amount of memory and the target will remain the same after
    reboot.
    
    This is still not quite a complete fix, as the 1MiB offset is only
    subtracted when creating or rebooting; it is not subtracted when 'xl
    set-memory' is called.  But it will prevent any situations where memory
    is continually increased or decreased.  A better fix will have to wait
    until after the release.
    
    Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
    Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    (cherry picked from commit 7e81d992b183c47a74eea5ecd613d27950b5cdc3)
---
 tools/libxl/libxl.c          |  8 ++++----
 tools/libxl/libxl_dom.c      | 10 ++--------
 tools/libxl/libxl_internal.h | 15 +++++++++++++++
 3 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index ac4a668..f22e01e 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -6721,12 +6721,12 @@ int libxl_retrieve_domain_configuration(libxl_ctx *ctx, 
uint32_t domid,
             LOG(ERROR, "fail to get memory target for domain %d", domid);
             goto out;
         }
-        /* Target memory in xenstore is different from what user has
-         * asked for. The difference is video_memkb. See
-         * libxl_set_memory_target.
+
+        /* libxl__get_targetmem_fudge() calculates the difference from
+         * what is in xenstore to what we have in the domain build info.
          */
         d_config->b_info.target_memkb = target_memkb +
-            d_config->b_info.video_memkb;
+            libxl__get_targetmem_fudge(gc, &d_config->b_info);
 
         d_config->b_info.max_memkb = max_memkb;
     }
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 2da3ac4..e2fd0eb 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -486,7 +486,6 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
     xs_transaction_t t;
     char **ents;
     int i, rc;
-    int64_t mem_target_fudge;
 
     if (info->num_vnuma_nodes && !info->num_vcpu_soft_affinity) {
         rc = set_vnuma_affinity(gc, domid, info);
@@ -519,17 +518,12 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
         }
     }
 
-    mem_target_fudge =
-        (info->type == LIBXL_DOMAIN_TYPE_HVM &&
-         info->max_memkb > info->target_memkb)
-        ? LIBXL_MAXMEM_CONSTANT : 0;
-
     ents = libxl__calloc(gc, 12 + (info->max_vcpus * 2) + 2, sizeof(char *));
     ents[0] = "memory/static-max";
     ents[1] = GCSPRINTF("%"PRId64, info->max_memkb);
     ents[2] = "memory/target";
-    ents[3] = GCSPRINTF("%"PRId64, info->target_memkb - info->video_memkb
-                        - mem_target_fudge);
+    ents[3] = GCSPRINTF("%"PRId64, info->target_memkb -
+                        libxl__get_targetmem_fudge(gc, info));
     ents[4] = "memory/videoram";
     ents[5] = GCSPRINTF("%"PRId64, info->video_memkb);
     ents[6] = "domid";
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 1f11b1a..a3597da 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -3943,6 +3943,21 @@ static inline void libxl__update_config_vtpm(libxl__gc 
*gc,
     libxl_uuid_copy(CTX, &dst->uuid, &src->uuid);
 }
 
+/* Target memory in xenstore is different from what user has
+ * asked for. The difference is video_memkb + (possible) fudge.
+ * See libxl_set_memory_target.
+ */
+static inline
+uint64_t libxl__get_targetmem_fudge(libxl__gc *gc,
+                                    const libxl_domain_build_info *info)
+{
+    int64_t mem_target_fudge = (info->type == LIBXL_DOMAIN_TYPE_HVM &&
+                                info->max_memkb > info->target_memkb)
+                                ? LIBXL_MAXMEM_CONSTANT : 0;
+
+    return info->video_memkb + mem_target_fudge;
+}
+
 /* Macros used to compare device identifier. Returns true if the two
  * devices have same identifier. */
 #define COMPARE_DEVID(a, b) ((a)->devid == (b)->devid)
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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