5 files changed, 57 insertions, 10 deletions

diff --git a/src/cpu/kvm/base.cc b/src/cpu/kvm/base.cc
index 32f94eca8..ea0f494e3 100644
--- a/src/cpu/kvm/base.cc
+++ b/src/cpu/kvm/base.cc
@@ -125,7 +125,7 @@ BaseKvmCPU::startup()
     const BaseKvmCPUParams * const p(
         dynamic_cast<const BaseKvmCPUParams *>(params()));
 
-    Kvm &kvm(vm.kvm);
+    Kvm &kvm(*vm.kvm);
 
     BaseCPU::startup();
 
@@ -363,6 +363,29 @@ BaseKvmCPU::drainResume()
 }
 
 void
+BaseKvmCPU::notifyFork()
+{
+    // We should have drained prior to forking, which means that the
+    // tick event shouldn't be scheduled and the CPU is idle.
+    assert(!tickEvent.scheduled());
+    assert(_status == Idle);
+
+    if (vcpuFD != -1) {
+        if (close(vcpuFD) == -1)
+            warn("kvm CPU: notifyFork failed to close vcpuFD\n");
+
+        if (_kvmRun)
+            munmap(_kvmRun, vcpuMMapSize);
+
+        vcpuFD = -1;
+        _kvmRun = NULL;
+
+        hwInstructions.detach();
+        hwCycles.detach();
+    }
+}
+
+void
 BaseKvmCPU::switchOut()
 {
     DPRINTF(Kvm, "switchOut\n");
@@ -617,6 +640,9 @@ Tick
 BaseKvmCPU::kvmRun(Tick ticks)
 {
     Tick ticksExecuted;
+    fatal_if(vcpuFD == -1,
+             "Trying to run a KVM CPU in a forked child process. "
+             "This is not supported.\n");
     DPRINTF(KvmRun, "KVM: Executing for %i ticks\n", ticks);
 
     if (ticks == 0) {
diff --git a/src/cpu/kvm/base.hh b/src/cpu/kvm/base.hh
index 4aeed2286..dd27328be 100644
--- a/src/cpu/kvm/base.hh
+++ b/src/cpu/kvm/base.hh
@@ -89,6 +89,7 @@ class BaseKvmCPU : public BaseCPU
 
     DrainState drain() override;
     void drainResume() override;
+    void notifyFork() override;
 
     void switchOut() override;
     void takeOverFrom(BaseCPU *cpu) override;
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
diff --git a/src/cpu/kvm/vm.hh b/src/cpu/kvm/vm.hh
index 8f834a06e..560efb606 100644
--- a/src/cpu/kvm/vm.hh
+++ b/src/cpu/kvm/vm.hh
@@ -295,6 +295,8 @@ class KvmVM : public SimObject
     KvmVM(KvmVMParams *params);
     virtual ~KvmVM();
 
+    void notifyFork();
+
     /**
      * Setup a shared three-page memory region used by the internals
      * of KVM. This is currently only needed by x86 implementations.
@@ -396,7 +398,7 @@ class KvmVM : public SimObject
     int createDevice(uint32_t type, uint32_t flags = 0);
 
     /** Global KVM interface */
-    Kvm kvm;
+    Kvm *kvm;
 
 #if defined(__aarch64__)
   public: // ARM-specific
@@ -504,7 +506,7 @@ class KvmVM : public SimObject
     System *system;
 
     /** KVM VM file descriptor */
-    const int vmFD;
+    int vmFD;
 
     /** Has delayedStartup() already been called? */
     bool started;
diff --git a/src/cpu/kvm/x86_cpu.cc b/src/cpu/kvm/x86_cpu.cc
index f3e5edaed..c6c874dc4 100644
--- a/src/cpu/kvm/x86_cpu.cc
+++ b/src/cpu/kvm/x86_cpu.cc
@@ -519,7 +519,7 @@ X86KvmCPU::X86KvmCPU(X86KvmCPUParams *params)
     : BaseKvmCPU(params),
       useXSave(params->useXSave)
 {
-    Kvm &kvm(vm.kvm);
+    Kvm &kvm(*vm.kvm);
 
     if (!kvm.capSetTSSAddress())
         panic("KVM: Missing capability (KVM_CAP_SET_TSS_ADDR)\n");
@@ -649,7 +649,7 @@ X86KvmCPU::dumpVCpuEvents() const
 void
 X86KvmCPU::dumpMSRs() const
 {
-    const Kvm::MSRIndexVector &supported_msrs(vm.kvm.getSupportedMSRs());
+    const Kvm::MSRIndexVector &supported_msrs(vm.kvm->getSupportedMSRs());
     std::unique_ptr<struct kvm_msrs> msrs(
         newVarStruct<struct kvm_msrs, struct kvm_msr_entry>(
             supported_msrs.size()));
@@ -1539,7 +1539,7 @@ const Kvm::MSRIndexVector &
 X86KvmCPU::getMsrIntersection() const
 {
     if (cachedMsrIntersection.empty()) {
-        const Kvm::MSRIndexVector &kvm_msrs(vm.kvm.getSupportedMSRs());
+        const Kvm::MSRIndexVector &kvm_msrs(vm.kvm->getSupportedMSRs());
 
         DPRINTF(Kvm, "kvm-x86: Updating MSR intersection\n");
         for (auto it = kvm_msrs.cbegin(); it != kvm_msrs.cend(); ++it) {