kvm: Shutdown KVM and disconnect performance counters on fork

We can't/shouldn't use KVM after a fork since the child and parent
probably point to the same VM. Knowing the exact effects of this is
hard, but they are likely to be messy. We also disconnect the
performance counters attached to the guest. This works around what
seems to be a kernel bug where spurious SIGIOs get delivered to the
forked child process.

Signed-off-by: Andreas Sandberg <andreas@sandberg.pp.se>
[sascha.bischoff@arm.com: Rebased patches onto a newer gem5 version]
Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
[andreas.sandberg@arm.com: Fatal if entering KVM in child process ]
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/src/cpu/kvm/vm.cc b/src/cpu/kvm/vm.cc
index 87a76c242..ccf739305 100644
--- a/src/cpu/kvm/vm.cc
+++ b/src/cpu/kvm/vm.cc
@@ -291,12 +291,12 @@ Kvm::createVM()
 
 KvmVM::KvmVM(KvmVMParams *params)
     : SimObject(params),
-      kvm(), system(params->system),
-      vmFD(kvm.createVM()),
+      kvm(new Kvm()), system(params->system),
+      vmFD(kvm->createVM()),
       started(false),
       nextVCPUID(0)
 {
-    maxMemorySlot = kvm.capNumMemSlots();
+    maxMemorySlot = kvm->capNumMemSlots();
     /* If we couldn't determine how memory slots there are, guess 32. */
     if (!maxMemorySlot)
         maxMemorySlot = 32;
@@ -307,7 +307,25 @@ KvmVM::KvmVM(KvmVMParams *params)
 
 KvmVM::~KvmVM()
 {
-    close(vmFD);
+    if (vmFD != -1)
+        close(vmFD);
+
+    if (kvm)
+        delete kvm;
+}
+
+void
+KvmVM::notifyFork()
+{
+    if (vmFD != -1) {
+        if (close(vmFD) == -1)
+            warn("kvm VM: notifyFork failed to close vmFD\n");
+
+        vmFD = -1;
+
+        delete kvm;
+        kvm = NULL;
+    }
 }
 
 void