Merge tag 'pull-hv-balloon-20240308' of https://github.com/maciejsszmigiero/qemu into staging

Hyper-V Dynamic Memory and VMBus misc small patches

This pull request contains two small patches to hv-balloon:
the first one replacing alloca() usage with g_malloc0() + g_autofree
and the second one adding additional declaration of a protocol message
struct with an optional field explicitly defined to avoid a Coverity
warning.

Also included is a VMBus patch to print a warning when it is enabled
without the recommended set of Hyper-V features (enlightenments) since
some Windows versions crash at boot in this case.

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* tag 'pull-hv-balloon-20240308' of https://github.com/maciejsszmigiero/qemu:
  vmbus: Print a warning when enabled without the recommended set of features
  hv-balloon: define dm_hot_add_with_region to avoid Coverity warning
  hv-balloon: avoid alloca() usage

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 26 insertions, 10 deletions

diff --git a/hw/hyperv/hv-balloon.c b/hw/hyperv/hv-balloon.c
index ade283335a..3a9ef07691 100644
--- a/hw/hyperv/hv-balloon.c
+++ b/hw/hyperv/hv-balloon.c
@@ -366,7 +366,7 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
     PageRangeTree dtree;
     uint64_t *dctr;
     bool our_range;
-    struct dm_unballoon_request *ur;
+    g_autofree struct dm_unballoon_request *ur = NULL;
     size_t ur_size = sizeof(*ur) + sizeof(ur->range_array[0]);
     PageRange range;
     bool bret;
@@ -388,8 +388,7 @@ static void hv_balloon_unballoon_posting(HvBalloon *balloon, StateDesc *stdesc)
     assert(dtree.t);
     assert(dctr);
 
-    ur = alloca(ur_size);
-    memset(ur, 0, ur_size);
+    ur = g_malloc0(ur_size);
     ur->hdr.type = DM_UNBALLOON_REQUEST;
     ur->hdr.size = ur_size;
     ur->hdr.trans_id = balloon->trans_id;
@@ -514,8 +513,8 @@ ret_idle:
 static void hv_balloon_hot_add_rb_wait(HvBalloon *balloon, StateDesc *stdesc)
 {
     VMBusChannel *chan = hv_balloon_get_channel(balloon);
-    struct dm_hot_add *ha;
-    size_t ha_size = sizeof(*ha) + sizeof(ha->range);
+    struct dm_hot_add_with_region *ha;
+    size_t ha_size = sizeof(*ha);
 
     assert(balloon->state == S_HOT_ADD_RB_WAIT);
 
@@ -531,8 +530,8 @@ static void hv_balloon_hot_add_posting(HvBalloon *balloon, StateDesc *stdesc)
     PageRange *hot_add_range = &balloon->hot_add_range;
     uint64_t *current_count = &balloon->ha_current_count;
     VMBusChannel *chan = hv_balloon_get_channel(balloon);
-    struct dm_hot_add *ha;
-    size_t ha_size = sizeof(*ha) + sizeof(ha->range);
+    g_autofree struct dm_hot_add_with_region *ha = NULL;
+    size_t ha_size = sizeof(*ha);
     union dm_mem_page_range *ha_region;
     uint64_t align, chunk_max_size;
     ssize_t ret;
@@ -560,9 +559,8 @@ static void hv_balloon_hot_add_posting(HvBalloon *balloon, StateDesc *stdesc)
      */
     *current_count = MIN(hot_add_range->count, chunk_max_size);
 
-    ha = alloca(ha_size);
-    ha_region = &(&ha->range)[1];
-    memset(ha, 0, ha_size);
+    ha = g_malloc0(ha_size);
+    ha_region = &ha->region;
     ha->hdr.type = DM_MEM_HOT_ADD_REQUEST;
     ha->hdr.size = ha_size;
     ha->hdr.trans_id = balloon->trans_id;
diff --git a/hw/hyperv/hyperv.c b/hw/hyperv/hyperv.c
index 6c4a18dd0e..3ea54ba818 100644
--- a/hw/hyperv/hyperv.c
+++ b/hw/hyperv/hyperv.c
@@ -951,3 +951,15 @@ uint64_t hyperv_syndbg_query_options(void)
 
     return msg.u.query_options.options;
 }
+
+static bool vmbus_recommended_features_enabled;
+
+bool hyperv_are_vmbus_recommended_features_enabled(void)
+{
+    return vmbus_recommended_features_enabled;
+}
+
+void hyperv_set_vmbus_recommended_features_enabled(void)
+{
+    vmbus_recommended_features_enabled = true;
+}
diff --git a/hw/hyperv/vmbus.c b/hw/hyperv/vmbus.c
index 380239af2c..f33afeeea2 100644
--- a/hw/hyperv/vmbus.c
+++ b/hw/hyperv/vmbus.c
@@ -2631,6 +2631,12 @@ static void vmbus_bridge_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    if (!hyperv_are_vmbus_recommended_features_enabled()) {
+        warn_report("VMBus enabled without the recommended set of Hyper-V features: "
+                    "hv-stimer, hv-vapic and hv-runtime. "
+                    "Some Windows versions might not boot or enable the VMBus device");
+    }
+
     bridge->bus = VMBUS(qbus_new(TYPE_VMBUS, dev, "vmbus"));
 }