KVM: VMX: fix invalid cpu passed to smp_call_function_single

In loaded_vmcs_clear, loaded_vmcs->cpu is the fist parameter passed to
smp_call_function_single, if the target cpu is downing (doing cpu hot remove),
loaded_vmcs->cpu can become -1 then -1 is passed to smp_call_function_single

It can be triggered when vcpu is being destroyed, loaded_vmcs_clear is called
in the preemptionable context

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index bb18923bf632..4406374e3b6d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1007,9 +1007,11 @@ static void __loaded_vmcs_clear(void *arg)
 
 static void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs)
 {
-        if (loaded_vmcs->cpu != -1)
-                smp_call_function_single(
-                        loaded_vmcs->cpu, __loaded_vmcs_clear, loaded_vmcs, 1);
+        int cpu = loaded_vmcs->cpu;
+
+        if (cpu != -1)
+                smp_call_function_single(cpu,
+                         __loaded_vmcs_clear, loaded_vmcs, 1);
 }
 
 static inline void vpid_sync_vcpu_single(struct vcpu_vmx *vmx)