Error writing to /dev/cpu/0/msr

[Viciouss]

Hi,

I wanted to undervolt the 5300G in my homelab but no matter what I try, I always get:

ERROR: Could not write data to /dev/cpu/0/msr

msr module is loaded, I tried both the -m cli option as well as the sys fs parameter. I'm using kernel 6.4.6 currently. Output of -g is:

Detected CPU model 50h, from family 19h with 8 CPU cores (REFCLK = 100MHz ; Voltage ID Encodings: SVI (serial)).

Core 0 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0

Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 1 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 2 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 3 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 4 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 5 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 6 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

Core 7 | P-State Limits (non-turbo): Highest: 0 ; Lowest 2 | Current P-State: 0
Pstate Status CpuFid CpuDid CpuVid CpuMult CpuFreq CpuVolt IddVal IddDiv CpuCurr CpuPower
0 1 160 8 32 40.00x 4000.00MHz 1350mV 40 10 50.00A 67.50W
1 1 102 12 96 17.00x 1700.00MHz 950mV 17 10 27.00A 25.65W
2 1 98 14 102 14.00x 1400.00MHz 912mV 14 10 24.00A 21.89W

cat /proc/cpuinfo:

processor : 0
vendor_id : AuthenticAMD
cpu family : 25
model : 80
model name : AMD Ryzen 3 5300G with Radeon Graphics
stepping : 0
microcode : 0xa50000c
cpu MHz : 2369.997
cache size : 512 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 16
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 erms invpcid cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd cppc arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip pku ospke vaes vpclmulqdq rdpid overflow_recov succor smca fsrm
bugs : sysret_ss_attrs spectre_v1 spectre_v2 spec_store_bypass
bogomips : 7988.39
TLB size : 2560 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm hwpstate cpb eff_freq_ro [13] [14]

Any help is appreciated.

Kind Regards
Martin

[AYuusuke]

Hi @Viciouss

I had similar error because of UEFI+SecureBoot mode:

# sudo dmesg | grep -e secureboot -e amdctl
[    0.000000] secureboot: Secure boot enabled
[    0.014819] secureboot: Secure boot enabled
[85917.978818] Lockdown: amdctl: raw MSR access is restricted; see man kernel_lockdown.7

Legacy BIOS mode works fine for me. Does it help?

[Viciouss]

Hey @AYuusuke

That did the trick, thank you very much!