x86/Kconfig: Introduce CONFIG_{AMD,INTEL} and conditionalise ucode

We eventually want to be able to build a stripped down Xen for a single
platform.  Make a start with CONFIG_{AMD,INTEL} (hidden behind EXPERT, but
available to randconfig), and adjust the microcode logic.

No practical change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/arch/x86/Kconfig

@@ -51,6 +51,8 @@ config HAS_CC_CET_IBT
 
 menu "Architecture Features"
 
+source "arch/x86/Kconfig.cpu"
+
 source "arch/Kconfig"
 
 config PV

xen/arch/x86/Kconfig.cpu

@@ -0,0 +1,22 @@
+menu "Supported CPU vendors"
+	visible if EXPERT
+
+config AMD
+	bool "Support AMD CPUs"
+	default y
+	help
+	  Detection, tunings and quirks for AMD platforms.
+
+	  May be turned off in builds targetting other vendors.  Otherwise,
+	  must be enabled for Xen to work suitably on AMD platforms.
+
+config INTEL
+	bool "Support Intel CPUs"
+	default y
+	help
+	  Detection, tunings and quirks for Intel platforms.
+
+	  May be turned off in builds targetting other vendors.  Otherwise,
+	  must be enabled for Xen to work suitably on Intel platforms.
+
+endmenu

xen/arch/x86/cpu/microcode/Makefile

@@ -1,3 +1,3 @@
-obj-y += amd.o
+obj-$(CONFIG_AMD) += amd.o
 obj-y += core.o
-obj-y += intel.o
+obj-$(CONFIG_INTEL) += intel.o

xen/arch/x86/cpu/microcode/private.h

@@ -70,7 +70,16 @@ struct microcode_ops {
  * support available) and (not) ops->apply_microcode (i.e. read only).
  * Otherwise, all hooks must be filled in.
  */
+#ifdef CONFIG_AMD
 void ucode_probe_amd(struct microcode_ops *ops);
+#else
+static inline void ucode_probe_amd(struct microcode_ops *ops) {}
+#endif
+
+#ifdef CONFIG_INTEL
 void ucode_probe_intel(struct microcode_ops *ops);
+#else
+static inline void ucode_probe_intel(struct microcode_ops *ops) {}
+#endif
 
 #endif /* ASM_X86_MICROCODE_PRIVATE_H */