diff options
| -rw-r--r-- | src/boot/efi/ticks.c | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/src/boot/efi/ticks.c b/src/boot/efi/ticks.c index 7dd808ae19..f902b83a99 100644 --- a/src/boot/efi/ticks.c +++ b/src/boot/efi/ticks.c @@ -5,6 +5,7 @@ #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 @@ -17,7 +18,35 @@ static uint64_t ticks_read_arch(void) { } static uint64_t ticks_freq_arch(void) { - return 0; + /* 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__) |