KVM: nVMX: Validate EFER values for VM_ENTRY/EXIT_LOAD_IA32_EFER

As we may emulate the loading of EFER on VM-entry and VM-exit, implement
the checks that VMX performs on the guest and host values on vmlaunch/
vmresume. Factor out kvm_valid_efer for this purpose which checks for
set reserved bits.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

3 files changed, 60 insertions, 10 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 599f98b612d4..18635ae42a8e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -809,6 +809,7 @@ static inline int emulate_instruction(struct kvm_vcpu *vcpu,
 }
 
 void kvm_enable_efer_bits(u64);
+bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
 int kvm_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *data);
 int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 11ea3cbbb78c..d7ef55686227 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -7558,6 +7558,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
         struct vcpu_vmx *vmx = to_vmx(vcpu);
         int cpu;
         struct loaded_vmcs *vmcs02;
+        bool ia32e;
 
         if (!nested_vmx_check_permission(vcpu) ||
             !nested_vmx_check_vmcs12(vcpu))
@@ -7649,6 +7650,45 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
         }
 
         /*
+         * If the “load IA32_EFER” VM-entry control is 1, the following checks
+         * are performed on the field for the IA32_EFER MSR:
+         * - Bits reserved in the IA32_EFER MSR must be 0.
+         * - Bit 10 (corresponding to IA32_EFER.LMA) must equal the value of
+         *   the IA-32e mode guest VM-exit control. It must also be identical
+         *   to bit 8 (LME) if bit 31 in the CR0 field (corresponding to
+         *   CR0.PG) is 1.
+         */
+        if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER) {
+                ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0;
+                if (!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer) ||
+                    ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA) ||
+                    ((vmcs12->guest_cr0 & X86_CR0_PG) &&
+                     ia32e != !!(vmcs12->guest_ia32_efer & EFER_LME))) {
+                        nested_vmx_entry_failure(vcpu, vmcs12,
+                                EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
+                        return 1;
+                }
+        }
+
+        /*
+         * If the load IA32_EFER VM-exit control is 1, bits reserved in the
+         * IA32_EFER MSR must be 0 in the field for that register. In addition,
+         * the values of the LMA and LME bits in the field must each be that of
+         * the host address-space size VM-exit control.
+         */
+        if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER) {
+                ia32e = (vmcs12->vm_exit_controls &
+                         VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
+                if (!kvm_valid_efer(vcpu, vmcs12->host_ia32_efer) ||
+                    ia32e != !!(vmcs12->host_ia32_efer & EFER_LMA) ||
+                    ia32e != !!(vmcs12->host_ia32_efer & EFER_LME)) {
+                        nested_vmx_entry_failure(vcpu, vmcs12,
+                                EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
+                        return 1;
+                }
+        }
+
+        /*
          * We're finally done with prerequisite checking, and can start with
          * the nested entry.
          */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e730a462ed05..2a434bf3918d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -845,23 +845,17 @@ static const u32 emulated_msrs[] = {
         MSR_IA32_MCG_CTL,
 };
 
-static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
+bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
-        u64 old_efer = vcpu->arch.efer;
-
         if (efer & efer_reserved_bits)
-                return 1;
-
-        if (is_paging(vcpu)
-            && (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME))
-                return 1;
+                return false;
 
         if (efer & EFER_FFXSR) {
                 struct kvm_cpuid_entry2 *feat;
 
                 feat = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
                 if (!feat || !(feat->edx & bit(X86_FEATURE_FXSR_OPT)))
-                        return 1;
+                        return false;
         }
 
         if (efer & EFER_SVME) {
@@ -869,9 +863,24 @@ static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
 
                 feat = kvm_find_cpuid_entry(vcpu, 0x80000001, 0);
                 if (!feat || !(feat->ecx & bit(X86_FEATURE_SVM)))
-                        return 1;
+                        return false;
         }
 
+        return true;
+}
+EXPORT_SYMBOL_GPL(kvm_valid_efer);
+
+static int set_efer(struct kvm_vcpu *vcpu, u64 efer)
+{
+        u64 old_efer = vcpu->arch.efer;
+
+        if (!kvm_valid_efer(vcpu, efer))
+                return 1;
+
+        if (is_paging(vcpu)
+            && (vcpu->arch.efer & EFER_LME) != (efer & EFER_LME))
+                return 1;
+
         efer &= ~EFER_LMA;
         efer |= vcpu->arch.efer & EFER_LMA;