[PATCH v2 1/1] migration/dirtyrate: Fix segmentation fault

[Masato Imai]

When the KVM acceleration parameter is not set, executing calc_dirty_rate
with the -r or -b option results in a segmentation fault due to accessing
a null kvm_state pointer in the kvm_dirty_ring_enabled function.
This commit adds a check for kvm_enabled to prevent segmentation faults.

Signed-off-by: Masato Imai <mii@sfc.wide.ad.jp>
---
 migration/dirtyrate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 1d2e85746f..2a7df52519 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -799,6 +799,13 @@ void qmp_calc_dirty_rate(int64_t calc_time,
      * dirty ring mode only works when kvm dirty ring is enabled.
      * on the contrary, dirty bitmap mode is not.
      */
+    if (!kvm_enabled() &&
+        (mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING ||
+         mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP)) {
+        error_setg(errp, "mode %s requires kvm to be enabled.",
+                         DirtyRateMeasureMode_str(mode));
+        return;
+    }
     if (((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
         !kvm_dirty_ring_enabled()) ||
         ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_BITMAP) &&
-- 
2.34.1