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fix(arch): add get_min_cpu_freq to Dvfs #741

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Merged
ytakano merged 2 commits into from
Oct 26, 2026
Merged

fix(arch): add get_min_cpu_freq to Dvfs #741

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17945bd
x86_64: add get_min_cpu_freq to Dvfs
Kanata9020 Oct 21, 2026
ea64da0
fix(arch): use Hz instead of MHz in x86_64 Dvfs implementation
Kanata9020 Oct 22, 2026
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37 changes: 29 additions & 8 deletions awkernel_lib/src/arch/x86_64/dvfs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,14 +13,23 @@ use super::X86;
mod hwpstate_intel;

const MSR_PLATFORM_INFO: u32 = 0xCE;
const MSR_PLATFORM_INFO_MAX_OFFSET: u32 = 8;
const MSR_PLATFORM_INFO_MIN_OFFSET: u32 = 40;
const IA32_PERF_MPERF: u32 = 0xE7;
const IA32_PERF_APERF: u32 = 0xE8;
const IA32_PERF_CTL: u32 = 0x199;
const IA32_MISC_ENABLE: u32 = 0x1A0;

fn bus_freq_mhz() -> u64 {
match (__cpuid(0x16).ecx & 0xffff) as u64 {
0 => 100, // Default to 100 MHz if bus frequency is not reported (old CPUs).
freq => freq,
}
}

impl Dvfs for X86 {
/// Fix the frequency of the current CPU.
fn set_cpu_freq(freq_mhz: u64) -> Result<()> {
fn set_cpu_freq(freq: u64) -> Result<()> {
unsafe {
let mut misc_enable = Msr::new(IA32_MISC_ENABLE);
let mut value = misc_enable.read();
Expand All @@ -31,9 +40,8 @@ impl Dvfs for X86 {
misc_enable.write(value);
}

let cpuid = __cpuid(0x16);
let bus_freq_mhz = (cpuid.ecx & 0xffff) as u64;
let target_pstate = ((freq_mhz / bus_freq_mhz) as u64) & 0xFFFF;
let bus_freq_mhz = bus_freq_mhz();
let target_pstate = (freq / bus_freq_mhz / 1_000_000) & 0xFFFF;
unsafe {
let mut perf_ctl = Msr::new(IA32_PERF_CTL);
let mut value = perf_ctl.read();
Expand All @@ -53,10 +61,21 @@ impl Dvfs for X86 {
fn get_max_cpu_freq() -> Result<u64> {
unsafe {
let platform_info = Msr::new(MSR_PLATFORM_INFO);
let max_ratio = (platform_info.read() >> 8) & 0xFF;
let bus_freq_mhz = (__cpuid(0x16).ecx & 0xffff) as u64;
let max_ratio = (platform_info.read() >> MSR_PLATFORM_INFO_MAX_OFFSET) & 0xFF;
let bus_freq_mhz = bus_freq_mhz();

Ok(max_ratio * bus_freq_mhz * 1_000_000)
}
}

/// Get the minimum frequency of the current CPU.
fn get_min_cpu_freq() -> Result<u64> {
unsafe {
let platform_info = Msr::new(MSR_PLATFORM_INFO);
let min_ratio = (platform_info.read() >> MSR_PLATFORM_INFO_MIN_OFFSET) & 0xFF;
let bus_freq_mhz = bus_freq_mhz();

Ok(max_ratio * bus_freq_mhz)
Ok(min_ratio * bus_freq_mhz * 1_000_000)
}
}

Expand All @@ -80,7 +99,9 @@ impl Dvfs for X86 {
let mperf_delta = mperf.read();
let aperf_delta = aperf.read();

Ok(aperf_delta * Self::get_max_cpu_freq().unwrap() / mperf_delta)
let max_cpu_freq_mhz = Self::get_max_cpu_freq()? / 1_000_000;

Ok(aperf_delta * max_cpu_freq_mhz / mperf_delta * 1_000_000)
}
}
}
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