KVM: SVM: retrieve VMCB from assembly

Continue moving accesses to struct vcpu_svm to vmenter.S.  Reducing the
number of arguments limits the chance of mistakes due to different
registers used for argument passing in 32- and 64-bit ABIs; pushing the
VMCB argument and almost immediately popping it into a different
register looks pretty weird.

32-bit ABI is not a concern for __svm_sev_es_vcpu_run() which is 64-bit
only; however, it will soon need @svm to save/restore SPEC_CTRL so stay
consistent with __svm_vcpu_run() and let them share the same prototype.

No functional change intended.

Cc: stable@vger.kernel.org
Fixes: a149180f ("x86: Add magic AMD return-thunk")
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/kvm-asm-offsets.c

@@ -15,6 +15,8 @@ static void __used common(void)
 	if (IS_ENABLED(CONFIG_KVM_AMD)) {
 		BLANK();
 		OFFSET(SVM_vcpu_arch_regs, vcpu_svm, vcpu.arch.regs);
+		OFFSET(SVM_current_vmcb, vcpu_svm, current_vmcb);
+		OFFSET(KVM_VMCB_pa, kvm_vmcb_info, pa);
 	}
 
 	if (IS_ENABLED(CONFIG_KVM_INTEL)) {

arch/x86/kvm/svm/svm.c

@@ -3914,12 +3914,11 @@ static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
-	unsigned long vmcb_pa = svm->current_vmcb->pa;
 
 	guest_state_enter_irqoff();
 
 	if (sev_es_guest(vcpu->kvm)) {
-		__svm_sev_es_vcpu_run(vmcb_pa);
+		__svm_sev_es_vcpu_run(svm);
 	} else {
 		struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
 
@@ -3930,7 +3929,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
 		 * vmcb02 when switching vmcbs for nested virtualization.
 		 */
 		vmload(svm->vmcb01.pa);
-		__svm_vcpu_run(vmcb_pa, svm);
+		__svm_vcpu_run(svm);
 		vmsave(svm->vmcb01.pa);
 
 		vmload(__sme_page_pa(sd->save_area));

arch/x86/kvm/svm/svm.h

@@ -683,7 +683,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm);
 
 /* vmenter.S */
 
-void __svm_sev_es_vcpu_run(unsigned long vmcb_pa);
-void __svm_vcpu_run(unsigned long vmcb_pa, struct vcpu_svm *svm);
+void __svm_sev_es_vcpu_run(struct vcpu_svm *svm);
+void __svm_vcpu_run(struct vcpu_svm *svm);
 
 #endif

arch/x86/kvm/svm/vmenter.S

@@ -32,7 +32,6 @@
 
 /**
  * __svm_vcpu_run - Run a vCPU via a transition to SVM guest mode
- * @vmcb_pa:	unsigned long
  * @svm:	struct vcpu_svm *
  */
 SYM_FUNC_START(__svm_vcpu_run)
@@ -49,16 +48,16 @@ SYM_FUNC_START(__svm_vcpu_run)
 	push %_ASM_BX
 
 	/* Save @svm. */
-	push %_ASM_ARG2
-
-	/* Save @vmcb. */
 	push %_ASM_ARG1
 
+.ifnc _ASM_ARG1, _ASM_DI
 	/* Move @svm to RDI. */
-	mov %_ASM_ARG2, %_ASM_DI
+	mov %_ASM_ARG1, %_ASM_DI
+.endif
 
-	/* "POP" @vmcb to RAX. */
-	pop %_ASM_AX
+	/* Get svm->current_vmcb->pa into RAX. */
+	mov SVM_current_vmcb(%_ASM_DI), %_ASM_AX
+	mov KVM_VMCB_pa(%_ASM_AX), %_ASM_AX
 
 	/* Load guest registers. */
 	mov VCPU_RCX(%_ASM_DI), %_ASM_CX
@@ -170,7 +169,7 @@ SYM_FUNC_END(__svm_vcpu_run)
 
 /**
  * __svm_sev_es_vcpu_run - Run a SEV-ES vCPU via a transition to SVM guest mode
- * @vmcb_pa:	unsigned long
+ * @svm:	struct vcpu_svm *
  */
 SYM_FUNC_START(__svm_sev_es_vcpu_run)
 	push %_ASM_BP
@@ -185,8 +184,9 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
 #endif
 	push %_ASM_BX
 
-	/* Move @vmcb to RAX. */
-	mov %_ASM_ARG1, %_ASM_AX
+	/* Get svm->current_vmcb->pa into RAX. */
+	mov SVM_current_vmcb(%_ASM_ARG1), %_ASM_AX
+	mov KVM_VMCB_pa(%_ASM_AX), %_ASM_AX
 
 	/* Enter guest mode */
 	sti