kvmvapic: Disable if there is insufficient memory

We need at least 1M of RAM to map the option ROM. Otherwise, we will
corrupt host memory or even crash:

    $ qemu-system-x86_64 -nodefaults --enable-kvm -vnc :0 -m 640k
    Segmentation fault (core dumped)

Reported-and-tested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
(cherry picked from commit a9605e0317c7a6d5e68f3a3b6708c8ef1096f4bc)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/hw/apic_common.c b/hw/apic_common.c
index 60b82596e7b6f3e8701c2b3246f853cf89804c90..e4612bbc755906e204ab987eef32103bcabd2727 100644 (file)
--- a/hw/apic_common.c
+++ b/hw/apic_common.c
@@ -289,7 +289,9 @@ static int apic_init_common(SysBusDevice *dev)
 
     sysbus_init_mmio(dev, &s->io_memory);
 
-    if (!vapic && s->vapic_control & VAPIC_ENABLE_MASK) {
+    /* Note: We need at least 1M to map the VAPIC option ROM */
+    if (!vapic && s->vapic_control & VAPIC_ENABLE_MASK &&
+        ram_size >= 1024 * 1024) {
         vapic = sysbus_create_simple("kvmvapic", -1, NULL);
     }
     s->vapic = vapic;