KVM: SVM: Enable Virtual VMLOAD VMSAVE feature

Enable the Virtual VMLOAD VMSAVE feature. This is done by setting bit 1
at position B8h in the vmcb.

The processor must have nested paging enabled, be in 64-bit mode and
have support for the Virtual VMLOAD VMSAVE feature for the bit to be set
in the vmcb.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/include/asm/svm.h

@@ -120,6 +120,7 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 #define AVIC_ENABLE_MASK (1 << AVIC_ENABLE_SHIFT)
 
 #define LBR_CTL_ENABLE_MASK BIT_ULL(0)
+#define VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK BIT_ULL(1)
 
 #define SVM_INTERRUPT_SHADOW_MASK 1
 

arch/x86/kvm/svm.c

@@ -277,6 +277,10 @@ static int avic;
 module_param(avic, int, S_IRUGO);
 #endif
 
+/* enable/disable Virtual VMLOAD VMSAVE */
+static int vls = true;
+module_param(vls, int, 0444);
+
 /* AVIC VM ID bit masks and lock */
 static DECLARE_BITMAP(avic_vm_id_bitmap, AVIC_VM_ID_NR);
 static DEFINE_SPINLOCK(avic_vm_id_lock);
@@ -1093,6 +1097,16 @@ static __init int svm_hardware_setup(void)
 		}
 	}
 
+	if (vls) {
+		if (!npt_enabled ||
+		    !boot_cpu_has(X86_FEATURE_VIRTUAL_VMLOAD_VMSAVE) ||
+		    !IS_ENABLED(CONFIG_X86_64)) {
+			vls = false;
+		} else {
+			pr_info("Virtual VMLOAD VMSAVE supported\n");
+		}
+	}
+
 	return 0;
 
 err:
@@ -1280,6 +1294,16 @@ static void init_vmcb(struct vcpu_svm *svm)
 	if (avic)
 		avic_init_vmcb(svm);
 
+	/*
+	 * If hardware supports Virtual VMLOAD VMSAVE then enable it
+	 * in VMCB and clear intercepts to avoid #VMEXIT.
+	 */
+	if (vls) {
+		clr_intercept(svm, INTERCEPT_VMLOAD);
+		clr_intercept(svm, INTERCEPT_VMSAVE);
+		svm->vmcb->control.virt_ext |= VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
+	}
+
 	mark_all_dirty(svm->vmcb);
 
 	enable_gif(svm);