xen/sched: Untangle credit2 vs cpu_nr_siblings()

Credit2 has no buisness including asm/cpufeature.h or asm/processor.h.

This was caused by a bad original abstraction, and an even less wise attempt
to fix the build on my behalf.  It is also the sole reason why PPC and RISC-V
need cpufeature.h header.

Worst of all, cpu_data[cpu].x86_num_siblings doesn't even have the same
meaning between vendors on x86 CPUS.

Implement cpu_nr_siblings() locally in credit2.c, leaving behind a TODO.  Drop
the stub from each architecture.

Fixes: 8e2aa76dc1 ("xen: credit2: limit the max number of CPUs in a runqueue")
Fixes: ad33a573c0 ("xen/credit2: Fix build following c/s 8e2aa76dc (take 2)")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Shawn Anastasio <sanastasio@raptorengineering.com>

xen/arch/arm/include/asm/cpufeature.h

@@ -98,11 +98,6 @@ static inline bool cpus_have_cap(unsigned int num)
     return test_bit(num, cpu_hwcaps);
 }
 
-static inline int cpu_nr_siblings(unsigned int cpu)
-{
-    return 1;
-}
-
 /* System capability check for constant cap */
 #define cpus_have_const_cap(num) ({                 \
         register_t __ret;                           \

xen/arch/ppc/include/asm/cpufeature.h

@@ -1,10 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-#ifndef __ASM_PPC_CPUFEATURE_H__
-#define __ASM_PPC_CPUFEATURE_H__
-
-static inline int cpu_nr_siblings(unsigned int cpu)
-{
-    return 1;
-}
-
-#endif /* __ASM_PPC_CPUFEATURE_H__ */

xen/arch/riscv/include/asm/cpufeature.h

@@ -1,23 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-#ifndef ASM__RISCV__CPUFEATURE_H
-#define ASM__RISCV__CPUFEATURE_H
-
-#ifndef __ASSEMBLY__
-
-static inline unsigned int cpu_nr_siblings(unsigned int cpu)
-{
-    return 1;
-}
-
-#endif /* __ASSEMBLY__ */
-
-#endif /* ASM__RISCV__CPUFEATURE_H */
-
-/*
- * Local variables:
- * mode: C
- * c-file-style: "BSD"
- * c-basic-offset: 4
- * indent-tabs-mode: nil
- * End:
- */

xen/arch/x86/include/asm/processor.h

@@ -118,11 +118,6 @@ extern void init_intel_cacheinfo(struct cpuinfo_x86 *c);
 
 unsigned int apicid_to_socket(unsigned int apicid);
 
-static inline int cpu_nr_siblings(unsigned int cpu)
-{
-    return cpu_data[cpu].x86_num_siblings;
-}
-
 /* Some CPUID calls want 'count' to be placed in ecx */
 static inline void cpuid_count(
     unsigned int op,

xen/common/sched/credit2.c

@@ -26,8 +26,6 @@
 #include <xen/trace.h>
 #include <xen/cpu.h>
 #include <xen/keyhandler.h>
-#include <asm/cpufeature.h>
-#include <asm/processor.h>
 
 #include "private.h"
 
@@ -35,6 +33,19 @@
 /* #define d2printk printk */
 #define d2printk(x...)
 
+/*
+ * TODO: Abstract this properly, and figure out what Credit2 wants to do with
+ *       the fact that x86_num_siblings doesn't even have the same meaning
+ *       between x86 vendors.
+ */
+static unsigned int cpu_nr_siblings(unsigned int cpu)
+{
+#ifdef CONFIG_X86
+    return cpu_data[cpu].x86_num_siblings;
+#else
+    return 1;
+#endif
+}
 
 /*
  * Credit2 tracing events ("only" 512 available!). Check