int msr;
unsigned long *msr_bitmap_l1;
unsigned long *msr_bitmap_l0 = vmx->nested.vmcs02.msr_bitmap;
+ struct hv_enlightened_vmcs *evmcs = vmx->nested.hv_evmcs;
struct kvm_host_map *map = &vmx->nested.msr_bitmap_map;
/* Nothing to do if the MSR bitmap is not in use. */
!nested_cpu_has(vmcs12, CPU_BASED_USE_MSR_BITMAPS))
return false;
+ /*
+ * MSR bitmap update can be skipped when:
+ * - MSR bitmap for L1 hasn't changed.
+ * - Nested hypervisor (L1) is attempting to launch the same L2 as
+ * before.
+ * - Nested hypervisor (L1) has enabled 'Enlightened MSR Bitmap' feature
+ * and tells KVM (L0) there were no changes in MSR bitmap for L2.
+ */
+ if (!vmx->nested.force_msr_bitmap_recalc && evmcs &&
+ evmcs->hv_enlightenments_control.msr_bitmap &&
+ evmcs->hv_clean_fields & HV_VMX_ENLIGHTENED_CLEAN_FIELD_MSR_BITMAP)
+ return true;
+
if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->msr_bitmap), map))
return false;