[XEN PATCH v1 2/2] x86/amd: optional build of amd.c

[Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>]

Similar to making Intel CPU support optional -- as we've got CONFIG_AMD option
now, we can put arch/x86/cpu/amd.c under it and make it possible to build
Xen without AMD CPU support. One possible use case is to dispose of dead code
in Intel-only systems.

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
---
 xen/arch/x86/cpu/Makefile      |  4 ++--
 xen/arch/x86/cpu/common.c      |  4 +++-
 xen/arch/x86/include/asm/amd.h | 22 ++++++++++++++++++++++
 xen/arch/x86/spec_ctrl.c       |  2 ++
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/cpu/Makefile b/xen/arch/x86/cpu/Makefile
index 020c86bda3..5efd87be38 100644
--- a/xen/arch/x86/cpu/Makefile
+++ b/xen/arch/x86/cpu/Makefile
@@ -2,10 +2,10 @@ obj-y += mcheck/
 obj-y += microcode/
 obj-y += mtrr/
 
-obj-y += amd.o
+obj-$(CONFIG_AMD) += amd.o
 obj-y += centaur.o
 obj-y += common.o
-obj-y += hygon.o
+obj-$(CONFIG_AMD) += hygon.o
 obj-$(CONFIG_INTEL) += intel.o
 obj-$(CONFIG_INTEL) += intel_cacheinfo.o
 obj-y += mwait-idle.o
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 50ce13f81c..7be689c2e3 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -341,9 +341,11 @@ void __init early_cpu_init(bool verbose)
                                  actual_cpu = intel_cpu_dev;    break;
        case X86_VENDOR_SHANGHAI: actual_cpu = shanghai_cpu_dev; break;
 #endif
+#ifdef CONFIG_AMD
        case X86_VENDOR_AMD:      actual_cpu = amd_cpu_dev;      break;
-       case X86_VENDOR_CENTAUR:  actual_cpu = centaur_cpu_dev;  break;
        case X86_VENDOR_HYGON:    actual_cpu = hygon_cpu_dev;    break;
+#endif
+       case X86_VENDOR_CENTAUR:  actual_cpu = centaur_cpu_dev;  break;
        default:
                actual_cpu = default_cpu;
                if (!verbose)
diff --git a/xen/arch/x86/include/asm/amd.h b/xen/arch/x86/include/asm/amd.h
index fa4e0fc766..a2481eddc7 100644
--- a/xen/arch/x86/include/asm/amd.h
+++ b/xen/arch/x86/include/asm/amd.h
@@ -158,13 +158,21 @@
 #define is_zen4_uarch()   boot_cpu_has(X86_FEATURE_AUTO_IBRS)
 
 struct cpuinfo_x86;
+#ifdef CONFIG_AMD
 int cpu_has_amd_erratum(const struct cpuinfo_x86 *cpu, int osvw_id, ...);
+#else
+static inline int cpu_has_amd_erratum(const struct cpuinfo_x86 *cpu, int 
osvw_id, ...)
+{
+    return false;
+}
+#endif
 
 extern s8 opt_allow_unsafe;
 
 void fam10h_check_enable_mmcfg(void);
 void check_enable_amd_mmconf_dmi(void);
 
+#ifdef CONFIG_AMD
 extern bool amd_acpi_c1e_quirk;
 void amd_check_disable_c1e(unsigned int port, u8 value);
 
@@ -173,5 +181,19 @@ extern bool amd_virt_spec_ctrl;
 bool amd_setup_legacy_ssbd(void);
 void amd_set_legacy_ssbd(bool enable);
 void amd_set_cpuid_user_dis(bool enable);
+#else
+static inline void amd_set_cpuid_user_dis(bool enable) {}
+static inline void amd_set_legacy_ssbd(bool enable) {}
+static inline bool amd_setup_legacy_ssbd(void)
+{
+    return false;
+}
+
+#define amd_acpi_c1e_quirk (false)
+#define amd_virt_spec_ctrl (false)
+#define amd_legacy_ssbd (false)
+
+static inline void amd_check_disable_c1e(unsigned int port, u8 value) {}
+#endif
 
 #endif /* __AMD_H__ */
diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index 92405b8be7..8231515c80 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -1884,10 +1884,12 @@ void __init init_speculation_mitigations(void)
             setup_force_cpu_cap(X86_FEATURE_SC_MSR_HVM);
     }
 
+#ifdef CONFIG_AMD
     /* Support VIRT_SPEC_CTRL.SSBD if AMD_SSBD is not available. */
     if ( opt_msr_sc_hvm && !cpu_has_amd_ssbd &&
          (cpu_has_virt_ssbd || (amd_legacy_ssbd && amd_setup_legacy_ssbd())) )
         amd_virt_spec_ctrl = true;
+#endif
 
     /* Figure out default_xen_spec_ctrl. */
     if ( has_spec_ctrl && ibrs )
-- 
2.25.1