[PATCH 6/8] x86/Intel: use host CPU policy for ARAT checking

[Jan Beulich <jbeulich@xxxxxxxx>]

There's no need to invoke CPUID yet another time. However, as the host CPU
policy is set up only shortly after init_intel() ran on the BSP, defer the
logic to a pre-SMP initcall. This can't be (a new) one in cpu/intel.c
though, as that's linked after acpi/cpu_idle.c (which is where we already
need the feature set). Since opt_arat is local to the cpu/ subtree,
introduce a new Intel-specific helper to hold the code needed.

Further, as we assume symmetry anyway, use setup_force_cpu_cap() and hence
limit the checking to the boot CPU.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
The need to move where cpu_has_arat is checked would go away if we did
away with opt_arat (as mentioned in the previous patch), and hence could
use cpu_has_arat directly where right now XEN_ARAT is checked.

--- a/xen/arch/x86/acpi/cpu_idle.c
+++ b/xen/arch/x86/acpi/cpu_idle.c
@@ -1666,6 +1666,9 @@ static int __init cf_check cpuidle_presm
 {
     void *cpu = (void *)(long)smp_processor_id();
 
+    if ( boot_cpu_data.vendor == X86_VENDOR_INTEL )
+        intel_init_arat();
+
     if ( !xen_cpuidle )
         return 0;
 
--- a/xen/arch/x86/cpu/intel.c
+++ b/xen/arch/x86/cpu/intel.c
@@ -665,10 +665,6 @@ static void cf_check init_intel(struct c
                __set_bit(X86_FEATURE_NONSTOP_TSC, c->x86_capability);
                __set_bit(X86_FEATURE_TSC_RELIABLE, c->x86_capability);
        }
-       if ( opt_arat &&
-            ( c->cpuid_level >= 0x00000006 ) &&
-            ( cpuid_eax(0x00000006) & (1u<<2) ) )
-               __set_bit(X86_FEATURE_XEN_ARAT, c->x86_capability);
 
        if ((opt_cpu_info && !(c->apicid & (c->x86_num_siblings - 1))) ||
            c == &boot_cpu_data )
@@ -690,3 +686,9 @@ const struct cpu_dev __initconst_cf_clob
        .c_early_init   = early_init_intel,
        .c_init         = init_intel,
 };
+
+void __init intel_init_arat(void)
+{
+    if ( opt_arat && cpu_has_arat )
+        setup_force_cpu_cap(X86_FEATURE_XEN_ARAT);
+}
--- a/xen/arch/x86/include/asm/cpufeature.h
+++ b/xen/arch/x86/include/asm/cpufeature.h
@@ -176,6 +176,9 @@ static inline bool boot_cpu_has(unsigned
 #define cpu_has_fma4            boot_cpu_has(X86_FEATURE_FMA4)
 #define cpu_has_tbm             boot_cpu_has(X86_FEATURE_TBM)
 
+/* CPUID level 0x00000006.eax */
+#define cpu_has_arat            host_cpu_policy.basic.pm.arat
+
 /* CPUID level 0x00000006.ecx */
 #define cpu_has_aperfmperf      host_cpu_policy.basic.pm.aperfmperf
 
--- a/xen/arch/x86/include/asm/processor.h
+++ b/xen/arch/x86/include/asm/processor.h
@@ -102,6 +102,7 @@ extern void setup_force_cpu_cap(unsigned
 extern bool is_forced_cpu_cap(unsigned int cap);
 extern void print_cpu_info(unsigned int cpu);
 extern void init_intel_cacheinfo(struct cpuinfo_x86 *c);
+extern void intel_init_arat(void);
 
 #define cpu_to_core(_cpu)   (cpu_data[_cpu].cpu_core_id)
 #define cpu_to_socket(_cpu) (cpu_data[_cpu].phys_proc_id)