[PATCH v4 19/47] x86/tsc: Add standalone helper for getting CPU frequency from CPUID

[Sean Christopherson <seanjc@xxxxxxxxxx>]

Extract the guts of cpu_khz_from_cpuid() to a standalone helper that
doesn't restrict the usage to Intel CPUs.  This will allow sharing the
core logic with KVM-as-a-guest, as KVM generally doesn't restrict CPUID
based on vendor.

No functional change intended.

Reviewed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/include/asm/tsc.h |  1 +
 arch/x86/kernel/tsc.c      | 32 +++++++++++++++-----------------
 2 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 4a224f99c3b9..7ff2bfdcdf38 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -90,6 +90,7 @@ struct cpuid_tsc_info {
        unsigned int tsc_khz;
 };
 extern int __init cpuid_get_tsc_freq(struct cpuid_tsc_info *info);
+extern unsigned int __cpu_khz_from_cpuid(void);
 
 extern void tsc_early_init(void);
 extern void tsc_init(void);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 3e911f0f7364..bdff8c988866 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -692,6 +692,18 @@ int __init cpuid_get_tsc_freq(struct cpuid_tsc_info *info)
        return 0;
 }
 
+unsigned int __cpu_khz_from_cpuid(void)
+{
+       unsigned int eax_base_mhz, ebx, ecx, edx;
+
+       if (boot_cpu_data.cpuid_level < CPUID_LEAF_FREQ)
+               return 0;
+
+       cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx, &ecx, &edx);
+
+       return eax_base_mhz * 1000;
+}
+
 /**
  * native_calibrate_tsc - determine TSC frequency
  * Determine TSC frequency via CPUID, else return 0.
@@ -727,13 +739,8 @@ static unsigned long native_calibrate_tsc(void)
         * clock, but we can easily calculate it to a high degree of accuracy
         * by considering the crystal ratio and the CPU speed.
         */
-       if (!info.crystal_khz && boot_cpu_data.cpuid_level >= CPUID_LEAF_FREQ) {
-               unsigned int eax_base_mhz, ebx, ecx, edx;
-
-               cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx, &ecx, &edx);
-               info.crystal_khz = eax_base_mhz * 1000 *
-                       info.denominator / info.numerator;
-       }
+       if (!info.crystal_khz)
+               info.crystal_khz = __cpu_khz_from_cpuid() * info.denominator / 
info.numerator;
 
        if (!info.crystal_khz)
                return 0;
@@ -760,19 +767,10 @@ static unsigned long native_calibrate_tsc(void)
 
 static unsigned long cpu_khz_from_cpuid(void)
 {
-       unsigned int eax_base_mhz, ebx_max_mhz, ecx_bus_mhz, edx;
-
        if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
                return 0;
 
-       if (boot_cpu_data.cpuid_level < CPUID_LEAF_FREQ)
-               return 0;
-
-       eax_base_mhz = ebx_max_mhz = ecx_bus_mhz = edx = 0;
-
-       cpuid(CPUID_LEAF_FREQ, &eax_base_mhz, &ebx_max_mhz, &ecx_bus_mhz, &edx);
-
-       return eax_base_mhz * 1000;
+       return __cpu_khz_from_cpuid();
 }
 
 /*
-- 
2.54.0.823.g6e5bcc1fc9-goog