[PATCH] qemu-kvm: fix segfault when running kvm without /dev/kvm, falling back to non-accelerated mode

From: Dustin Kirkland <kirkland@canonical.com>
To: qemu-devel@nongnu.org, kvm@vger.kernel.org
Subject: [PATCH] qemu-kvm: fix segfault when running kvm without /dev/kvm, falling back to non-accelerated mode
Date: Thu, 3 Sep 2009 12:31:33 -0500	[thread overview]
Message-ID: <d9c105ea0909031031g463aa731j846dd73d4c158ebc@mail.gmail.com> (raw)

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qemu-kvm: fix segfault when running kvm without /dev/kvm, falling back
to non-accelerated mode

We're seeing segfaults on systems without access to /dev/kvm.  It
looks like the global kvm_allowed is being set just a little too late
in vl.c.  This patch moves the kvm initialization a bit higher in the
vl.c main, just after options processing, and solves the segfaults.
We're carrying this patch in Ubuntu 9.10 Alpha.  Please apply
upstream, or advise if and why this might not be the optimal solution.

Signed-off-by: Dustin Kirkland <kirkland@canonical.com>

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Move the kvm_init() call a bit higher to fix a segfault when
/dev/kvm is not available.  The kvm_allowed global needs
to be set correctly a little earlier.

Signed-off-by: Dustin Kirkland <kirkland@canonical.com>

--- qemu-kvm-0.11.0~rc1.orig/vl.c
+++ qemu-kvm-0.11.0~rc1/vl.c
@@ -5748,6 +5748,20 @@
         }
     }
 
+    if (kvm_enabled()) {
+        int ret;
+
+        ret = kvm_init(smp_cpus);
+        if (ret < 0) {
+#if defined(KVM_UPSTREAM) || defined(NO_CPU_EMULATION)
+            fprintf(stderr, "failed to initialize KVM\n");
+            exit(1);
+#endif
+            fprintf(stderr, "Could not initialize KVM, will disable KVM support\n");
+            kvm_allowed = 0;
+        }
+    }
+
     /* If no data_dir is specified then try to find it relative to the
        executable path.  */
     if (!data_dir) {
@@ -6008,20 +6022,6 @@
         }
     }
 
-    if (kvm_enabled()) {
-        int ret;
-
-        ret = kvm_init(smp_cpus);
-        if (ret < 0) {
-#if defined(KVM_UPSTREAM) || defined(NO_CPU_EMULATION)
-            fprintf(stderr, "failed to initialize KVM\n");
-            exit(1);
-#endif
-            fprintf(stderr, "Could not initialize KVM, will disable KVM support\n");
-	     kvm_allowed = 0;
-        }
-    }
-
     if (monitor_device) {
         monitor_hd = qemu_chr_open("monitor", monitor_device, NULL);
         if (!monitor_hd) {
