KVM: SVM: improve split between svm_prepare_guest_switch and sev_es_prepare_guest_switch

KVM performs the VMSAVE to the host save area for both regular and SEV-ES
guests, so hoist it up to svm_prepare_guest_switch.  And because
sev_es_prepare_guest_switch does not really need to know the details
of struct svm_cpu_data *, just pass it the pointer to the host save area
inside the HSAVE page.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/sev.c

@@ -2907,20 +2907,16 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
 					    sev_enc_bit));
 }
 
-void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu)
+void sev_es_prepare_guest_switch(struct vmcb_save_area *hostsa)
 {
-	struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
-	struct vmcb_save_area *hostsa;
-
 	/*
 	 * As an SEV-ES guest, hardware will restore the host state on VMEXIT,
-	 * of which one step is to perform a VMLOAD. Since hardware does not
-	 * perform a VMSAVE on VMRUN, the host savearea must be updated.
+	 * of which one step is to perform a VMLOAD.  KVM performs the
+	 * corresponding VMSAVE in svm_prepare_guest_switch for both
+	 * traditional and SEV-ES guests.
 	 */
-	vmsave(__sme_page_pa(sd->save_area));
 
 	/* XCR0 is restored on VMEXIT, save the current host value */
-	hostsa = (struct vmcb_save_area *)(page_address(sd->save_area) + 0x400);
 	hostsa->xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
 
 	/* PKRU is restored on VMEXIT, save the current host value */

arch/x86/kvm/svm/svm.c

@@ -1280,10 +1280,12 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu)
 	 * Save additional host state that will be restored on VMEXIT (sev-es)
 	 * or subsequent vmload of host save area.
 	 */
+	vmsave(__sme_page_pa(sd->save_area));
 	if (sev_es_guest(vcpu->kvm)) {
-		sev_es_prepare_guest_switch(svm, vcpu->cpu);
-	} else {
-		vmsave(__sme_page_pa(sd->save_area));
+		struct vmcb_save_area *hostsa;
+		hostsa = (struct vmcb_save_area *)(page_address(sd->save_area) + 0x400);
+
+		sev_es_prepare_guest_switch(hostsa);
 	}
 
 	if (tsc_scaling) {

arch/x86/kvm/svm/svm.h

@@ -606,7 +606,7 @@ int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
 void sev_es_init_vmcb(struct vcpu_svm *svm);
 void sev_es_vcpu_reset(struct vcpu_svm *svm);
 void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
-void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu);
+void sev_es_prepare_guest_switch(struct vmcb_save_area *hostsa);
 void sev_es_unmap_ghcb(struct vcpu_svm *svm);
 
 /* vmenter.S */