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kernel/x86: Don't disable the CPUID/MSR TSC frequency read on hypervisor.

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It was disabled when adding the hypervisor CPUID leaf reading to
the bootloader, but that's not really necessary. This way, if
a hypervisor does not provide that CPUID leaf but does provide
the value in the standard CPUID or MSR, we will still read it
correctly anyway.
This commit is contained in:
Augustin Cavalier
2024-09-10 17:07:10 -04:00
parent 1e13801271
commit 1705e9761a
1 changed files with 5 additions and 5 deletions
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src/system/kernel/arch/x86/arch_cpu.cpp
+5 -5
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@@ -1575,6 +1575,7 @@ init_tsc_with_cpuid(kernel_args* args, uint32* conversionFactor)
cpu_ent* cpu = get_cpu_struct();
if (cpu->arch.vendor != VENDOR_INTEL)
return;
uint32 model = (cpu->arch.extended_model << 4) | cpu->arch.model;
cpuid_info cpuid;
get_current_cpuid(&cpuid, 0, 0);
@@ -1600,6 +1601,7 @@ init_tsc_with_cpuid(kernel_args* args, uint32* conversionFactor)
}
if (khz == 0)
return;
dprintf("CPU: using TSC frequency from CPUID\n");
// compute for microseconds as follows (1000000 << 32) / (tsc freq in Hz),
// or (1000 << 32) / (tsc freq in kHz)
@@ -1615,6 +1617,7 @@ init_tsc_with_msr(kernel_args* args, uint32* conversionFactor)
cpu_ent* cpuEnt = get_cpu_struct();
if (cpuEnt->arch.vendor != VENDOR_AMD)
return;
uint32 family = cpuEnt->arch.family + cpuEnt->arch.extended_family;
if (family < 0x10)
return;
@@ -1654,13 +1657,10 @@ init_tsc(kernel_args* args)
// try to find the TSC frequency with CPUID
uint32 conversionFactor = args->arch_args.system_time_cv_factor;
if (!x86_check_feature(IA32_FEATURE_EXT_HYPERVISOR, FEATURE_EXT)) {
init_tsc_with_cpuid(args, &conversionFactor);
init_tsc_with_msr(args, &conversionFactor);
}
init_tsc_with_cpuid(args, &conversionFactor);
init_tsc_with_msr(args, &conversionFactor);
uint64 conversionFactorNsecs = (uint64)conversionFactor * 1000;
#ifdef __x86_64__
// The x86_64 system_time() implementation uses 64-bit multiplication and
// therefore shifting is not necessary for low frequencies (it's also not