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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "ticks.h"
#include "util.h"
#include "vmm.h"
#if defined(__i386__) || defined(__x86_64__)
# include <cpuid.h>
static uint64_t ticks_read_arch(void) {
/* The TSC might or might not be virtualized in VMs (and thus might not be accurate or start at zero
* at boot), depending on hypervisor and CPU functionality. If it's not virtualized it's not useful
* for keeping time, hence don't attempt to use it. */
if (in_hypervisor())
return 0;
return __builtin_ia32_rdtsc();
}
static uint64_t ticks_freq_arch(void) {
/* Detect TSC frequency from CPUID information if available. */
unsigned max_leaf, ebx, ecx, edx;
if (__get_cpuid(0, &max_leaf, &ebx, &ecx, &edx) == 0)
return 0;
/* Leaf 0x15 is Intel only. */
if (max_leaf < 0x15 || ebx != signature_INTEL_ebx || ecx != signature_INTEL_ecx ||
edx != signature_INTEL_edx)
return 0;
unsigned denominator, numerator, crystal_hz;
__cpuid(0x15, denominator, numerator, crystal_hz, edx);
if (denominator == 0 || numerator == 0)
return 0;
uint64_t freq = crystal_hz;
if (crystal_hz == 0) {
/* If the crystal frquency is not available, try to deduce it from
* the processor frequency leaf if available. */
if (max_leaf < 0x16)
return 0;
unsigned core_mhz;
__cpuid(0x16, core_mhz, ebx, ecx, edx);
freq = core_mhz * 1000ULL * 1000ULL * denominator / numerator;
}
return freq * numerator / denominator;
}
#elif defined(__aarch64__)
static uint64_t ticks_read_arch(void) {
uint64_t val;
asm volatile("mrs %0, cntvct_el0" : "=r"(val));
return val;
}
static uint64_t ticks_freq_arch(void) {
uint64_t freq;
asm volatile("mrs %0, cntfrq_el0" : "=r"(freq));
return freq;
}
#else
static uint64_t ticks_read_arch(void) {
return 0;
}
static uint64_t ticks_freq_arch(void) {
return 0;
}
#endif
static uint64_t ticks_freq(void) {
static uint64_t cache = 0;
if (cache != 0)
return cache;
cache = ticks_freq_arch();
if (cache != 0)
return cache;
/* As a fallback, count ticks during a millisecond delay. */
uint64_t ticks_start = ticks_read_arch();
BS->Stall(1000);
uint64_t ticks_end = ticks_read_arch();
if (ticks_end < ticks_start) /* Check for an overflow (which is not that unlikely, given on some
* archs the value is 32bit) */
return 0;
cache = (ticks_end - ticks_start) * 1000UL;
return cache;
}
uint64_t time_usec(void) {
uint64_t ticks = ticks_read_arch();
if (ticks == 0)
return 0;
uint64_t freq = ticks_freq();
if (freq == 0)
return 0;
return 1000UL * 1000UL * ticks / freq;
}
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