[XEN PATCH v2 5/5] 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>
CC: Jan Beulich <jbeulich@xxxxxxxx>
---
changes in v2:
 - drop routines-stubs in amd.h, handle call sites instead
 - cpu_has_amd_erratum() return int instead of bool
---
 xen/arch/x86/cpu/Makefile      |  2 +-
 xen/arch/x86/cpu/common.c      |  4 +++-
 xen/arch/x86/hvm/svm/svm.c     |  6 ++++--
 xen/arch/x86/include/asm/amd.h | 20 ++++++++++++++++++--
 xen/arch/x86/spec_ctrl.c       |  2 ++
 5 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/cpu/Makefile b/xen/arch/x86/cpu/Makefile
index eeb9ebe562..2c34597136 100644
--- a/xen/arch/x86/cpu/Makefile
+++ b/xen/arch/x86/cpu/Makefile
@@ -2,7 +2,7 @@ obj-y += mcheck/
 obj-y += microcode/
 obj-y += mtrr/
 
-obj-y += amd.o
+obj-$(CONFIG_AMD) += amd.o
 obj-$(CONFIG_CENTAUR) += centaur.o
 obj-y += common.o
 obj-$(CONFIG_HYGON) += hygon.o
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 580b01d6d5..5930b712bf 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -194,7 +194,7 @@ void ctxt_switch_levelling(const struct vcpu *next)
 
                if (cpu_has_cpuid_faulting)
                        set_cpuid_faulting(enable_cpuid_faulting);
-               else
+               else if ( IS_ENABLED(CONFIG_AMD) )
                        amd_set_cpuid_user_dis(enable_cpuid_faulting);
 
                return;
@@ -340,7 +340,9 @@ void __init early_cpu_init(bool verbose)
        case X86_VENDOR_INTEL:    intel_unlock_cpuid_leaves(c);
                                  actual_cpu = intel_cpu_dev;    break;
 #endif
+#ifdef CONFIG_AMD
        case X86_VENDOR_AMD:      actual_cpu = amd_cpu_dev;      break;
+#endif
 #ifdef CONFIG_CENTAUR
        case X86_VENDOR_CENTAUR:  actual_cpu = centaur_cpu_dev;  break;
 #endif
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 92bb10c504..88902e2d3a 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -919,7 +919,8 @@ static void cf_check svm_ctxt_switch_from(struct vcpu *v)
      * Possibly clear previous guest selection of SSBD if set.  Note that
      * SPEC_CTRL.SSBD is already handled by svm_vmexit_spec_ctrl.
      */
-    if ( v->arch.msrs->virt_spec_ctrl.raw & SPEC_CTRL_SSBD )
+    if ( IS_ENABLED(CONFIG_AMD) &&
+         v->arch.msrs->virt_spec_ctrl.raw & SPEC_CTRL_SSBD )
     {
         ASSERT(v->domain->arch.cpuid->extd.virt_ssbd);
         amd_set_legacy_ssbd(false);
@@ -953,7 +954,8 @@ static void cf_check svm_ctxt_switch_to(struct vcpu *v)
         wrmsr_tsc_aux(v->arch.msrs->tsc_aux);
 
     /* Load SSBD if set by the guest. */
-    if ( v->arch.msrs->virt_spec_ctrl.raw & SPEC_CTRL_SSBD )
+    if ( IS_ENABLED(CONFIG_AMD) &&
+         v->arch.msrs->virt_spec_ctrl.raw & SPEC_CTRL_SSBD )
     {
         ASSERT(v->domain->arch.cpuid->extd.virt_ssbd);
         amd_set_legacy_ssbd(true);
diff --git a/xen/arch/x86/include/asm/amd.h b/xen/arch/x86/include/asm/amd.h
index fa4e0fc766..da35b82d5a 100644
--- a/xen/arch/x86/include/asm/amd.h
+++ b/xen/arch/x86/include/asm/amd.h
@@ -158,20 +158,36 @@
 #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 0;
+}
+#endif
 
 extern s8 opt_allow_unsafe;
 
 void fam10h_check_enable_mmcfg(void);
 void check_enable_amd_mmconf_dmi(void);
 
-extern bool amd_acpi_c1e_quirk;
 void amd_check_disable_c1e(unsigned int port, u8 value);
 
 extern bool amd_legacy_ssbd;
-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);
 
+#ifdef CONFIG_AMD
+extern bool amd_acpi_c1e_quirk;
+extern bool amd_virt_spec_ctrl;
+#else
+
+#define amd_acpi_c1e_quirk (false)
+#define amd_virt_spec_ctrl (false)
+
+#endif
+
 #endif /* __AMD_H__ */
diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index ba6c3e80d2..1964a417de 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -1893,10 +1893,12 @@ 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