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x86_cstates: Log errors indicating why C-states can't be used.

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As long as we have MWAIT and invariant TSC, anyway.

Also add a check for VENDOR_INTEL for the C5/C6 state disabling.
This commit is contained in:
Augustin Cavalier
2025-09-17 15:19:37 -04:00
parent 358e90524a
commit 39a01464d8
1 changed files with 19 additions and 9 deletions
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src/add-ons/kernel/power/cpuidle/x86_cstates/x86_cstates.cpp
+19 -9
View File
@@ -139,25 +139,34 @@ init_cstates()
cpuid_info cpuid;
get_current_cpuid(&cpuid, 0, 0);
uint32 maxBasicLeaf = cpuid.eax_0.max_eax;
if (maxBasicLeaf < IA32_CPUID_LEAF_MWAIT)
if (maxBasicLeaf < IA32_CPUID_LEAF_MWAIT) {
dprintf("can't use x86 C-States: no CPUID leaf for MWAIT\n");
return B_ERROR;
}
get_current_cpuid(&cpuid, IA32_CPUID_LEAF_MWAIT, 0);
uint32 minMonitorLineSize = cpuid.regs.eax & 0xffff;
//uint32 maxMonitorLineSize = cpuid.regs.ebx & 0xffff;
uint32 mwaitSubStates = cpuid.regs.edx;
if (minMonitorLineSize < sizeof(int32))
uint32 mwaitSubStates = cpuid.regs.edx;
if (minMonitorLineSize < sizeof(int32)) {
dprintf("can't use x86 C-States: line size too small\n");
return B_ERROR;
if (mwaitSubStates == 0)
}
if (mwaitSubStates == 0) {
dprintf("can't use x86 C-States: no MWAIT sub-states\n");
return B_ERROR;
}
// check Enumeration of Monitor-Mwait extensions is supported
// and check treating interrupts as break-events even when interrupts disabled is supported
if ((cpuid.regs.ecx & CPUID_MWAIT_ECX_SUPPORT) != CPUID_MWAIT_ECX_SUPPORT)
if ((cpuid.regs.ecx & CPUID_MWAIT_ECX_SUPPORT) != CPUID_MWAIT_ECX_SUPPORT) {
dprintf("can't use x86 C-States: extensions missing\n");
return B_ERROR;
}
cpu_ent* cpu = &gCPU[0];
uint8 model = cpu->arch.model + (cpu->arch.extended_model << 4);
if (cpu->arch.family == 6) {
if (cpu->arch.vendor == VENDOR_INTEL && cpu->arch.family == 6) {
// disable C5 and C6 states on Skylake (same as Linux)
if (model == 0x5e && (mwaitSubStates & (0xf << 28)) != 0)
mwaitSubStates &= 0xf00fffff;
@@ -181,8 +190,10 @@ init_cstates()
sCStateCount++;
}
if (sCStateCount == 0)
if (sCStateCount == 0) {
dprintf("can't use x86 C-States: none found\n");
return B_ERROR;
}
sIdleTime = new(std::nothrow) bigtime_t[smp_get_num_cpus()];
if (sIdleTime == NULL)
@@ -191,7 +202,7 @@ init_cstates()
cstates_set_scheduler_mode(SCHEDULER_MODE_LOW_LATENCY);
dprintf("using Intel C-States: C0%s\n", cStates);
dprintf("using x86 C-States: C0%s\n", cStates);
return B_OK;
}
@@ -240,4 +251,3 @@ module_info* modules[] = {
(module_info*)&sX86CStates,
NULL
};