target/i386/sev: Remove stubs by using code elision

Only declare sev_enabled() and sev_es_enabled() when CONFIG_SEV is
set, to allow the compiler to elide unused code. Remove unnecessary
stubs.

Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: philmd

target/i386/cpu.c

@@ -5764,12 +5764,13 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         *edx = 0;
         break;
     case 0x8000001F:
-        *eax = sev_enabled() ? 0x2 : 0;
-        *eax |= sev_es_enabled() ? 0x8 : 0;
-        *ebx = sev_get_cbit_position();
-        *ebx |= sev_get_reduced_phys_bits() << 6;
-        *ecx = 0;
-        *edx = 0;
+        *eax = *ebx = *ecx = *edx = 0;
+        if (sev_enabled()) {
+            *eax = 0x2;
+            *eax |= sev_es_enabled() ? 0x8 : 0;
+            *ebx = sev_get_cbit_position();
+            *ebx |= sev_get_reduced_phys_bits() << 6;
+        }
         break;
     default:
         /* reserved values: zero */

target/i386/meson.build

@@ -6,7 +6,7 @@ i386_ss.add(files(
   'xsave_helper.c',
   'cpu-dump.c',
 ))
-i386_ss.add(when: 'CONFIG_SEV', if_true: files('host-cpu.c'), if_false: files('sev-stub.c'))
+i386_ss.add(when: 'CONFIG_SEV', if_true: files('host-cpu.c'))
 
 # x86 cpu type
 i386_ss.add(when: 'CONFIG_KVM', if_true: files('host-cpu.c'))

target/i386/sev-stub.c

@@ -14,6 +14,10 @@
 #ifndef QEMU_SEV_I386_H
 #define QEMU_SEV_I386_H
 
+#ifndef CONFIG_USER_ONLY
+#include CONFIG_DEVICES /* CONFIG_SEV */
+#endif
+
 #include "exec/confidential-guest-support.h"
 #include "qapi/qapi-types-misc-target.h"
 
@@ -35,8 +39,14 @@ typedef struct SevKernelLoaderContext {
     size_t cmdline_size;
 } SevKernelLoaderContext;
 
+#ifdef CONFIG_SEV
 bool sev_enabled(void);
-extern bool sev_es_enabled(void);
+bool sev_es_enabled(void);
+#else
+#define sev_enabled() 0
+#define sev_es_enabled() 0
+#endif
+
 extern SevInfo *sev_get_info(void);
 extern uint32_t sev_get_cbit_position(void);
 extern uint32_t sev_get_reduced_phys_bits(void);