[PATCH v3 1/5] KVM: nVMX: generate non-true VMX MSRs based on true versions

[David Matlack]

The "non-true" VMX capability MSRs can be generated from their "true"
counterparts, by OR-ing the default1 bits. The default1 bits are fixed
and defined in the SDM.

Since we can generate the non-true VMX MSRs from the true versions,
there's no need to store both in struct nested_vmx. This also lets
userspace avoid having to restore the non-true MSRs.

Note this does not preclude emulating MSR_IA32_VMX_BASIC[55]=0. To do so,
we simply need to set all the default1 bits in the true MSRs (such that
the true MSRs and the generated non-true MSRs are equal).

Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 45 +++++++++++++++++++--------------------------
 1 file changed, 19 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5382b82..0beb56a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -446,19 +446,21 @@ struct nested_vmx {
 	u16 vpid02;
 	u16 last_vpid;
 
+	/*
+	 * We only store the "true" versions of the VMX capability MSRs. We
+	 * generate the "non-true" versions by setting the must-be-1 bits
+	 * according to the SDM.
+	 */
 	u32 nested_vmx_procbased_ctls_low;
 	u32 nested_vmx_procbased_ctls_high;
-	u32 nested_vmx_true_procbased_ctls_low;
 	u32 nested_vmx_secondary_ctls_low;
 	u32 nested_vmx_secondary_ctls_high;
 	u32 nested_vmx_pinbased_ctls_low;
 	u32 nested_vmx_pinbased_ctls_high;
 	u32 nested_vmx_exit_ctls_low;
 	u32 nested_vmx_exit_ctls_high;
-	u32 nested_vmx_true_exit_ctls_low;
 	u32 nested_vmx_entry_ctls_low;
 	u32 nested_vmx_entry_ctls_high;
-	u32 nested_vmx_true_entry_ctls_low;
 	u32 nested_vmx_misc_low;
 	u32 nested_vmx_misc_high;
 	u32 nested_vmx_ept_caps;
@@ -2712,9 +2714,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 		vmx->nested.nested_vmx_exit_ctls_high |= VM_EXIT_CLEAR_BNDCFGS;
 
 	/* We support free control of debug control saving. */
-	vmx->nested.nested_vmx_true_exit_ctls_low =
-		vmx->nested.nested_vmx_exit_ctls_low &
-		~VM_EXIT_SAVE_DEBUG_CONTROLS;
+	vmx->nested.nested_vmx_exit_ctls_low &= ~VM_EXIT_SAVE_DEBUG_CONTROLS;
 
 	/* entry controls */
 	rdmsr(MSR_IA32_VMX_ENTRY_CTLS,
@@ -2733,9 +2733,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 		vmx->nested.nested_vmx_entry_ctls_high |= VM_ENTRY_LOAD_BNDCFGS;
 
 	/* We support free control of debug control loading. */
-	vmx->nested.nested_vmx_true_entry_ctls_low =
-		vmx->nested.nested_vmx_entry_ctls_low &
-		~VM_ENTRY_LOAD_DEBUG_CONTROLS;
+	vmx->nested.nested_vmx_entry_ctls_low &= ~VM_ENTRY_LOAD_DEBUG_CONTROLS;
 
 	/* cpu-based controls */
 	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS,
@@ -2768,8 +2766,7 @@ static void nested_vmx_setup_ctls_msrs(struct vcpu_vmx *vmx)
 		CPU_BASED_USE_MSR_BITMAPS;
 
 	/* We support free control of CR3 access interception. */
-	vmx->nested.nested_vmx_true_procbased_ctls_low =
-		vmx->nested.nested_vmx_procbased_ctls_low &
+	vmx->nested.nested_vmx_procbased_ctls_low &=
 		~(CPU_BASED_CR3_LOAD_EXITING | CPU_BASED_CR3_STORE_EXITING);
 
 	/* secondary cpu-based controls */
@@ -2868,36 +2865,32 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
 		*pdata = vmx_control_msr(
 			vmx->nested.nested_vmx_pinbased_ctls_low,
 			vmx->nested.nested_vmx_pinbased_ctls_high);
+		if (msr_index == MSR_IA32_VMX_PINBASED_CTLS)
+			*pdata |= PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
 		break;
 	case MSR_IA32_VMX_TRUE_PROCBASED_CTLS:
-		*pdata = vmx_control_msr(
-			vmx->nested.nested_vmx_true_procbased_ctls_low,
-			vmx->nested.nested_vmx_procbased_ctls_high);
-		break;
 	case MSR_IA32_VMX_PROCBASED_CTLS:
 		*pdata = vmx_control_msr(
 			vmx->nested.nested_vmx_procbased_ctls_low,
 			vmx->nested.nested_vmx_procbased_ctls_high);
+		if (msr_index == MSR_IA32_VMX_PROCBASED_CTLS)
+			*pdata |= CPU_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
 		break;
 	case MSR_IA32_VMX_TRUE_EXIT_CTLS:
-		*pdata = vmx_control_msr(
-			vmx->nested.nested_vmx_true_exit_ctls_low,
-			vmx->nested.nested_vmx_exit_ctls_high);
-		break;
 	case MSR_IA32_VMX_EXIT_CTLS:
 		*pdata = vmx_control_msr(
 			vmx->nested.nested_vmx_exit_ctls_low,
 			vmx->nested.nested_vmx_exit_ctls_high);
+		if (msr_index == MSR_IA32_VMX_EXIT_CTLS)
+			*pdata |= VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR;
 		break;
 	case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
-		*pdata = vmx_control_msr(
-			vmx->nested.nested_vmx_true_entry_ctls_low,
-			vmx->nested.nested_vmx_entry_ctls_high);
-		break;
 	case MSR_IA32_VMX_ENTRY_CTLS:
 		*pdata = vmx_control_msr(
 			vmx->nested.nested_vmx_entry_ctls_low,
 			vmx->nested.nested_vmx_entry_ctls_high);
+		if (msr_index == MSR_IA32_VMX_ENTRY_CTLS)
+			*pdata |= VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR;
 		break;
 	case MSR_IA32_VMX_MISC:
 		*pdata = vmx_control_msr(
@@ -10184,7 +10177,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	}
 
 	if (!vmx_control_verify(vmcs12->cpu_based_vm_exec_control,
-				vmx->nested.nested_vmx_true_procbased_ctls_low,
+				vmx->nested.nested_vmx_procbased_ctls_low,
 				vmx->nested.nested_vmx_procbased_ctls_high) ||
 	    !vmx_control_verify(vmcs12->secondary_vm_exec_control,
 				vmx->nested.nested_vmx_secondary_ctls_low,
@@ -10193,10 +10186,10 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 				vmx->nested.nested_vmx_pinbased_ctls_low,
 				vmx->nested.nested_vmx_pinbased_ctls_high) ||
 	    !vmx_control_verify(vmcs12->vm_exit_controls,
-				vmx->nested.nested_vmx_true_exit_ctls_low,
+				vmx->nested.nested_vmx_exit_ctls_low,
 				vmx->nested.nested_vmx_exit_ctls_high) ||
 	    !vmx_control_verify(vmcs12->vm_entry_controls,
-				vmx->nested.nested_vmx_true_entry_ctls_low,
+				vmx->nested.nested_vmx_entry_ctls_low,
 				vmx->nested.nested_vmx_entry_ctls_high))
 	{
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-- 
2.8.0.rc3.226.g39d4020