Extract retrieval of TSC frequency information from CPUID into standalone
helpers so that TDX guest support and kvmlock can reuse the logic. Provide
a version that includes the multiplier math as TDX in particular does NOT
want to use native_calibrate_tsc()'s fallback logic that derives the TSC
frequency based on CPUID.0x16 when the core crystal frequency isn't known.
Opportunsitically drop native_calibrate_tsc()'s "== 0" and "!= 0" check
in favor of the kernel's preferred style.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/include/asm/tsc.h | 9 +++++
arch/x86/kernel/tsc.c | 67 +++++++++++++++++++++++++-------------
2 files changed, 53 insertions(+), 23 deletions(-)
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94408a784c8e..a4d84f721775 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -28,6 +28,15 @@ static inline cycles_t get_cycles(void)
}
#define get_cycles get_cycles
+struct cpuid_tsc_info {
+ unsigned int denominator;
+ unsigned int numerator;
+ unsigned int crystal_khz;
+ unsigned int tsc_khz;
+};
+extern int cpuid_get_tsc_info(struct cpuid_tsc_info *info);
+extern int cpuid_get_tsc_freq(struct cpuid_tsc_info *info);
+
extern void tsc_early_init(void);
extern void tsc_init(void);
extern void mark_tsc_unstable(char *reason);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 34dec0b72ea8..93713eb81f52 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -655,46 +655,67 @@ static unsigned long quick_pit_calibrate(void)
return delta;
}
+int cpuid_get_tsc_info(struct cpuid_tsc_info *info)
+{
+ unsigned int ecx_hz, edx;
+
+ memset(info, 0, sizeof(*info));
+
+ if (boot_cpu_data.cpuid_level < CPUID_LEAF_TSC)
+ return -ENOENT;
+
+ /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
+ cpuid(CPUID_LEAF_TSC, &info->denominator, &info->numerator, &ecx_hz, &edx);
+
+ if (!info->denominator || !info->numerator)
+ return -ENOENT;
+
+ /*
+ * Note, some CPUs provide the multiplier information, but not the core
+ * crystal frequency. The multiplier information is still useful for
+ * such CPUs, as the crystal frequency can be gleaned from CPUID.0x16.
+ */
+ info->crystal_khz = ecx_hz / 1000;
+ return 0;
+}
+
+int cpuid_get_tsc_freq(struct cpuid_tsc_info *info)
+{
+ if (cpuid_get_tsc_info(info) || !info->crystal_khz)
+ return -ENOENT;
+
+ info->tsc_khz = info->crystal_khz * info->numerator / info->denominator;
+ return 0;
+}
+
/**
* native_calibrate_tsc - determine TSC frequency
* Determine TSC frequency via CPUID, else return 0.
*/
unsigned long native_calibrate_tsc(void)
{
- unsigned int eax_denominator, ebx_numerator, ecx_hz, edx;
- unsigned int crystal_khz;
+ struct cpuid_tsc_info info;
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
return 0;
- if (boot_cpu_data.cpuid_level < CPUID_LEAF_TSC)
+ if (cpuid_get_tsc_info(&info))
return 0;
- eax_denominator = ebx_numerator = ecx_hz = edx = 0;
-
- /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
- cpuid(CPUID_LEAF_TSC, &eax_denominator, &ebx_numerator, &ecx_hz, &edx);
-
- if (ebx_numerator == 0 || eax_denominator == 0)
- return 0;
-
- crystal_khz = ecx_hz / 1000;
-
/*
* Denverton SoCs don't report crystal clock, and also don't support
* CPUID_LEAF_FREQ for the calculation below, so hardcode the 25MHz
* crystal clock.
*/
- if (crystal_khz == 0 &&
- boot_cpu_data.x86_vfm == INTEL_ATOM_GOLDMONT_D)
- crystal_khz = 25000;
+ if (!info.crystal_khz && boot_cpu_data.x86_vfm == INTEL_ATOM_GOLDMONT_D)
+ info.crystal_khz = 25000;
/*
* TSC frequency reported directly by CPUID is a "hardware reported"
* frequency and is the most accurate one so far we have. This
* is considered a known frequency.
*/
- if (crystal_khz != 0)
+ if (info.crystal_khz)
setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
/*
@@ -702,15 +723,15 @@ 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 (crystal_khz == 0 && boot_cpu_data.cpuid_level >= CPUID_LEAF_FREQ) {
+ 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);
- crystal_khz = eax_base_mhz * 1000 *
- eax_denominator / ebx_numerator;
+ info.crystal_khz = eax_base_mhz * 1000 *
+ info.denominator / info.numerator;
}
- if (crystal_khz == 0)
+ if (!info.crystal_khz)
return 0;
/*
@@ -727,10 +748,10 @@ unsigned long native_calibrate_tsc(void)
* lapic_timer_period here to avoid having to calibrate the APIC
* timer later.
*/
- lapic_timer_period = crystal_khz * 1000 / HZ;
+ lapic_timer_period = info.crystal_khz * 1000 / HZ;
#endif
- return crystal_khz * ebx_numerator / eax_denominator;
+ return info.crystal_khz * info.numerator / info.denominator;
}
static unsigned long cpu_khz_from_cpuid(void)
--
2.48.1.711.g2feabab25a-goog
