[21/22] KVM: nVMX: Support VMCS shadowing virtualization

Commit Message

Liran Alon June 22, 2018, 11:35 p.m. UTC

L0 now sets up controls for vmcs02 so that L2 can perform
unintercepted VMREADs and VMWRITEs as specified in the vmcs12 controls
(though VMCS fields not supported by L0 will still cause VM-exits).

A boolean was added to vmx->nested to indicate if vmcs02 use VMCS
shadowing to avoid executing VMREADs to deduce it as a performance
optimization.

Signed-off-by: Liran Alon <[e-mail]>
Signed-off-by: Jim Mattson <[e-mail]>
---
 arch/x86/kvm/vmx.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 94922adf6f47..4b63d6bae6bd 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -675,6 +675,7 @@  struct nested_vmx {
 	bool pi_pending;
 	u16 posted_intr_nv;
 
+	bool virtualize_shadow_vmcs;
 	unsigned long *vmread_bitmap;
 	unsigned long *vmwrite_bitmap;
 
@@ -10918,6 +10919,8 @@  static void vmx_inject_page_fault_nested(struct kvm_vcpu *vcpu,
 
 static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
 						 struct vmcs12 *vmcs12);
+static inline bool nested_vmx_setup_shadow_bitmaps(struct kvm_vcpu *vcpu,
+						   struct vmcs12 *vmcs12);
 
 static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu,
 					struct vmcs12 *vmcs12)
@@ -11007,6 +11010,15 @@  static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu,
 	else
 		vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,
 				CPU_BASED_USE_MSR_BITMAPS);
+
+	if (vmx->nested.virtualize_shadow_vmcs) {
+		if (nested_vmx_setup_shadow_bitmaps(vcpu, vmcs12)) {
+			copy_shadow_vmcs12_to_shadow_vmcs02(vmx);
+		} else {
+			vmx->nested.virtualize_shadow_vmcs = false;
+			vmx_disable_shadow_vmcs(vmx);
+		}
+	}
 }
 
 static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu)
@@ -11287,6 +11299,9 @@  static void nested_flush_cached_shadow_vmcs12(struct kvm_vcpu *vcpu,
 	    vmcs12->vmcs_link_pointer == -1ull)
 		return;
 
+	if (vmx->nested.virtualize_shadow_vmcs)
+		copy_shadow_vmcs02_to_shadow_vmcs12(to_vmx(vcpu));
+
 	kvm_write_guest(vmx->vcpu.kvm, vmcs12->vmcs_link_pointer,
 			get_shadow_vmcs12(vcpu), VMCS12_SIZE);
 }
@@ -11849,7 +11864,10 @@  static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		 * VMCS shadowing, virtualize VMCS shadowing by
 		 * allocating a shadow VMCS and vmread/vmwrite bitmaps
 		 * for vmcs02. vmread/vmwrite bitmaps are init at this
-		 * point to intercept all vmread/vmwrite.
+		 * point to intercept all vmread/vmwrite. Later,
+		 * nested_get_vmcs12_pages() will either update bitmaps to
+		 * handle some vmread/vmwrite by hardware or remove
+		 * VMCS shadowing from vmcs02.
 		 *
 		 * Otherwise, emulate VMCS shadowing by disabling VMCS
 		 * shadowing at vmcs02 and emulate vmread/vmwrite to
@@ -11860,10 +11878,12 @@  static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		 * back to VMCS shadowing emulation if
 		 * nested_vmcs_fields_per_group() > BITS_PER_LONG.
 		 */
-		if ((exec_control & SECONDARY_EXEC_SHADOW_VMCS) &&
-		    enable_shadow_vmcs &&
-		    nested_vmcs_fields_per_group(vmx) <= BITS_PER_LONG &&
-		    !alloc_vmcs_shadowing_pages(vcpu)) {
+		vmx->nested.virtualize_shadow_vmcs =
+			(exec_control & SECONDARY_EXEC_SHADOW_VMCS) &&
+			enable_shadow_vmcs &&
+			nested_vmcs_fields_per_group(vmx) <= BITS_PER_LONG &&
+			!alloc_vmcs_shadowing_pages(vcpu);
+		if (vmx->nested.virtualize_shadow_vmcs) {
 			vmcs_write64(VMCS_LINK_POINTER,
 				     vmcs12->vmcs_link_pointer == -1ull ?
 				     -1ull : __pa(vmx->loaded_vmcs->shadow_vmcs));
@@ -12236,8 +12256,6 @@  static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu)
 	if (prepare_vmcs02(vcpu, vmcs12, &exit_qual))
 		goto fail;
 
-	nested_get_vmcs12_pages(vcpu, vmcs12);
-
 	r = EXIT_REASON_MSR_LOAD_FAIL;
 	msr_entry_idx = nested_vmx_load_msr(vcpu,
 					    vmcs12->vm_entry_msr_load_addr,
@@ -12364,6 +12382,12 @@  static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 * exist on destination host yet).
 	 */
 	nested_cache_shadow_vmcs12(vcpu, vmcs12);
+	/*
+	 * Must be called after nested_cache_shadow_vmcs12()
+	 * because it may internally copy cached shadow vmcs12
+	 * into shadow vmcs02.
+	 */
+	nested_get_vmcs12_pages(vcpu, vmcs12);
 
 	/*
 	 * If we're entering a halted L2 vcpu and the L2 vcpu won't be woken