KVM: nVMX: mask unrestricted_guest if disabled on L0

If EPT was enabled, unrestricted_guest was allowed in L1 regardless of
L0.  L1 triple faulted when running L2 guest that required emulation.

Another side effect was 'WARN_ON_ONCE(vmx->nested.nested_run_pending)'
in L0's dmesg:
  WARNING: CPU: 0 PID: 0 at arch/x86/kvm/vmx.c:9190 nested_vmx_vmexit+0x96e/0xb00 [kvm_intel] ()

Prevent this scenario by masking SECONDARY_EXEC_UNRESTRICTED_GUEST when
the host doesn't have it enabled.

Fixes: 78051e3b7e35 ("KVM: nVMX: Disable unrestricted mode if ept=0")
Cc: stable@vger.kernel.org
Tested-By: Kashyap Chamarthy <kchamart@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 10a481b..ae4f6d3 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2479,8 +2479,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
        if (enable_ept) {
                /* nested EPT: emulate EPT also to L1 */
                vmx->nested.nested_vmx_secondary_ctls_high |=
-                       SECONDARY_EXEC_ENABLE_EPT |
-                       SECONDARY_EXEC_UNRESTRICTED_GUEST;
+                       SECONDARY_EXEC_ENABLE_EPT;
                vmx->nested.nested_vmx_ept_caps = VMX_EPT_PAGE_WALK_4_BIT |
                         VMX_EPTP_WB_BIT | VMX_EPT_2MB_PAGE_BIT |
                         VMX_EPT_INVEPT_BIT;
@@ -2494,6 +2493,10 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
        } else
                vmx->nested.nested_vmx_ept_caps = 0;
 
+       if (enable_unrestricted_guest)
+               vmx->nested.nested_vmx_secondary_ctls_high |=
+                       SECONDARY_EXEC_UNRESTRICTED_GUEST;
+
        /* miscellaneous data */
        rdmsr(MSR_IA32_VMX_MISC,
                vmx->nested.nested_vmx_misc_low,