KVM: nVMX: Allow setting the VMXE bit in CR4

This patch allows the guest to enable the VMXE bit in CR4, which is a
prerequisite to running VMXON.

Whether to allow setting the VMXE bit now depends on the architecture (svm
or vmx), so its checking has moved to kvm_x86_ops->set_cr4(). This function
now returns an int: If kvm_x86_ops->set_cr4() returns 1, __kvm_set_cr4()
will also return 1, and this will cause kvm_set_cr4() will throw a #GP.

Turning on the VMXE bit is allowed only when the nested VMX feature is
enabled, and turning it off is forbidden after a vmxon.

Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d88de565d0c0..460932b62c5b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -615,11 +615,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
                                    kvm_read_cr3(vcpu)))
                 return 1;
 
-        if (cr4 & X86_CR4_VMXE)
+        if (kvm_x86_ops->set_cr4(vcpu, cr4))
                 return 1;
 
-        kvm_x86_ops->set_cr4(vcpu, cr4);
-
         if ((cr4 ^ old_cr4) & pdptr_bits)
                 kvm_mmu_reset_context(vcpu);