x86/boot/compressed: Only build mem_encrypt.S if AMD_MEM_ENCRYPT=y

Avoid building the mem_encrypt.o object if memory encryption support is
not enabled to begin with.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221122161017.2426828-17-ardb@kernel.org

arch/x86/boot/compressed/Makefile

@@ -100,7 +100,7 @@ vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
 ifdef CONFIG_X86_64
 	vmlinux-objs-y += $(obj)/ident_map_64.o
 	vmlinux-objs-y += $(obj)/idt_64.o $(obj)/idt_handlers_64.o
-	vmlinux-objs-y += $(obj)/mem_encrypt.o
+	vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/mem_encrypt.o
 	vmlinux-objs-y += $(obj)/pgtable_64.o
 	vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/sev.o
 endif

arch/x86/boot/compressed/mem_encrypt.S

@@ -307,7 +307,6 @@ SYM_FUNC_END(startup32_check_sev_cbit)
 
 	.data
 
-#ifdef CONFIG_AMD_MEM_ENCRYPT
 	.balign	8
 SYM_DATA(sme_me_mask,		.quad 0)
 SYM_DATA(sev_status,		.quad 0)
@@ -323,4 +322,3 @@ SYM_DATA_START_LOCAL(boot32_idt_desc)
 	.word	. - boot32_idt - 1
 	.long	0
 SYM_DATA_END(boot32_idt_desc)
-#endif