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setting CPU_FLAGS_X86 during stage 3 install from Minimal
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Lambduh
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Joined: 01 Aug 2019
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PostPosted: Thu Aug 01, 2019 9:59 pm    Post subject: setting CPU_FLAGS_X86 during stage 3 install from Minimal Reply with quote

Hey all, First time Gentoo user here. I work in the field but have been working with prepackaged systems for a long time. Go easy on me ;)

Essentially, I'm going through the handbook and I am at the point where I am to set my Emerge make.conf vars. I have been looking around a lot and cannot seem to find this topic at all, other than people inputting the wrong variables and getting bad results... which I don't want. Forgive me if I'm just looking in the wrong place.

In the handbook:
https://wiki.gentoo.org/wiki/GCC_optimization

They state that you can determine your CPU flags using /proc/cpuinfo, but that it's easier using the cpuid utility. Unfortunately, I do not have this utility on the minimal install ISO, and the CPUID utility's output seems to be a touch more condensed than that of the flags section in /proc/cpuinfo.

My question is:
Is there a way to determine which flags should be set in CPU_FLAGS_X86 without the CPUID utility, and if so how is this determined. Otherwise, should all flags in the flag section of /proc/cpuinfo be used? Below is my output:
Code:
livecd ~ # grep flags /proc/cpuinfo | sort | uniq
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp


That's a whole lot of flags, I'm sure many of those are implied by having my march flag set to skylake, or maybe I'm reading into this in the wrong way entirely.

Either way, thank you for your time in advance!
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Jaglover
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Joined: 29 May 2005
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PostPosted: Thu Aug 01, 2019 10:14 pm    Post subject: Reply with quote

Welcome to Gentoo!

There is no need to set CPU_FLAGS_X86 during base system install. Install the base system, reboot into your Gentoo and then, with network up, start installing other software, including app-portage/cpuid2cpuflags. For CFLAGS use -march=native.
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Lambduh
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PostPosted: Thu Aug 01, 2019 11:01 pm    Post subject: Reply with quote

Thanks for the input! I'll do that then. Much appreciated.
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