[PULL,22/31] exec: keep ram block across fork when using qtest

Commit Message

Stefan Hajnoczi Feb. 22, 2020, 8:50 a.m. UTC

From: Alexander Bulekov <[e-mail]>

Ram blocks were marked MADV_DONTFORK breaking fuzzing-tests which
execute each test-input in a forked process.

Signed-off-by: Alexander Bulekov <[e-mail]>
Reviewed-by: Stefan Hajnoczi <[e-mail]>
Reviewed-by: Darren Kenny <[e-mail]>
Message-id: [e-mail]
Signed-off-by: Stefan Hajnoczi <[e-mail]>
---
 exec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

Patch

diff --git a/exec.c b/exec.c
index 8e9cc3b47c..c930040f83 100644
--- a/exec.c
+++ b/exec.c
@@ -35,6 +35,7 @@ 
 #include "sysemu/kvm.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/tcg.h"
+#include "sysemu/qtest.h"
 #include "qemu/timer.h"
 #include "qemu/config-file.h"
 #include "qemu/error-report.h"
@@ -2305,8 +2306,15 @@  static void ram_block_add(RAMBlock *new_block, Error **errp, bool shared)
     if (new_block->host) {
         qemu_ram_setup_dump(new_block->host, new_block->max_length);
         qemu_madvise(new_block->host, new_block->max_length, QEMU_MADV_HUGEPAGE);
-        /* MADV_DONTFORK is also needed by KVM in absence of synchronous MMU */
-        qemu_madvise(new_block->host, new_block->max_length, QEMU_MADV_DONTFORK);
+        /*
+         * MADV_DONTFORK is also needed by KVM in absence of synchronous MMU
+         * Configure it unless the machine is a qtest server, in which case
+         * KVM is not used and it may be forked (eg for fuzzing purposes).
+         */
+        if (!qtest_enabled()) {
+            qemu_madvise(new_block->host, new_block->max_length,
+                         QEMU_MADV_DONTFORK);
+        }
         ram_block_notify_add(new_block->host, new_block->max_length);
     }
 }