Re: [PATCH] KVM: nVMX: Unrestricted guest mode requires EPT

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On 08/30/2018 04:05 PM, Jim Mattson wrote:
As specified in Intel's SDM, do not allow the L1 hypervisor to launch
an L2 guest with the VM-execution controls for "unrestricted guest" or
"mode-based execute control for EPT" set and the VM-execution control
for "enable EPT" clear.

Note that the VM-execution control for "mode-based execute control for
EPT" is not yet virtualized by kvm.

Reported-by: Andrew Thornton <andrewth@xxxxxxxxxx>
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: Peter Shier <pshier@xxxxxxxxxx>
---
  arch/x86/include/asm/vmx.h |  1 +
  arch/x86/kvm/vmx.c         | 13 +++++++++++++
  2 files changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 9527ba5d62da..665632a4b54b 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -78,6 +78,7 @@
  #define SECONDARY_EXEC_RDSEED_EXITING		0x00010000
  #define SECONDARY_EXEC_ENABLE_PML               0x00020000
  #define SECONDARY_EXEC_XSAVES			0x00100000
+#define SECONDARY_EXEC_MODE_BASED_EPT_EXEC	0x00400000
  #define SECONDARY_EXEC_TSC_SCALING              0x02000000
#define PIN_BASED_EXT_INTR_MASK 0x00000001
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1d26f3c4985b..2bf990b5848f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11719,6 +11719,16 @@ static int nested_vmx_check_pml_controls(struct kvm_vcpu *vcpu,
  	return 0;
  }
+static int nested_vmx_check_ept_enable(struct kvm_vcpu *vcpu,
+				       struct vmcs12 *vmcs12)
+{
+	if ((nested_cpu_has2(vmcs12, SECONDARY_EXEC_UNRESTRICTED_GUEST) ||
+	     nested_cpu_has2(vmcs12, SECONDARY_EXEC_MODE_BASED_EPT_EXEC)) &&
+	    !nested_cpu_has_ept(vmcs12))
+		return -EINVAL;
+	return 0;
+}
+
  static int nested_vmx_check_shadow_vmcs_controls(struct kvm_vcpu *vcpu,
  						 struct vmcs12 *vmcs12)
  {
@@ -12339,6 +12349,9 @@ static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
  	if (nested_vmx_check_pml_controls(vcpu, vmcs12))
  		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+ if (nested_vmx_check_ept_enable(vcpu, vmcs12))
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+
  	if (nested_vmx_check_shadow_vmcs_controls(vcpu, vmcs12))
  		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>



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