[gentoo-user] kernel config strangeness

[gentoo-user] kernel config strangeness

[Jack]

I just built a new PC, and I'm having a problem getting it to boot with  
a custom configured kernel (gentoo-sources-5.2.4.)  If I start with a  
blank config and work through "make xconfig" the resulting kernel and  
initramfs (genkernel) doesn't boot (just hangs after loading  
initramfs.)  So, starting with the config from the running kernel from  
the live install medium, running make oldconfig then genkernel, it  
boots fine.  I assume my problem is removing something important while  
trying to remove all the unnecessary options for supporting hardware  
I'll never use.

However, if I start with the .config which workd, and "make xconfig"  
and select "Supported processor types" under "Processor type and  
features" and then unselect "Support Intel Pprocessors" (I have a  
Ryzen) and save the config, it decreases the size of .config from 169K  
to under 13K, losing almost every setting in the file.

Even stranger, if I look at "Local version - append to kernel release:"  
it still shows the value I had previously set - but that setting  
CONFIG_LOCALVERSION is NOT in .config.  If I close the tool and start  
it again, that setting is now missing and it looks like all settings  
have been reset to the clean starting defaults (i.e., many say "(NEW)"

Am I missing something here, or might this really be a bug in "make  
xconfig" ?

Can anyone else replicate this?  While I don't think it's related to my  
problem getting a non-booting kernel, it certainly has me confused.

Thanks for helping me confirm what's left of my sanity.

Jack

Re: [gentoo-user] kernel config strangeness

[Mick]

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On Wednesday, 31 July 2019 23:31:20 BST Jack wrote:
> I just built a new PC, and I'm having a problem getting it to boot with
> a custom configured kernel (gentoo-sources-5.2.4.)  If I start with a
> blank config and work through "make xconfig" the resulting kernel and
> initramfs (genkernel) doesn't boot (just hangs after loading
> initramfs.)  

Does it spit out any errors on the console?


> So, starting with the config from the running kernel from
> the live install medium, running make oldconfig then genkernel, it
> boots fine.  I assume my problem is removing something important while
> trying to remove all the unnecessary options for supporting hardware
> I'll never use.
> 
> However, if I start with the .config which workd, and "make xconfig"
> and select "Supported processor types" under "Processor type and
> features" and then unselect "Support Intel Pprocessors" (I have a
> Ryzen) and save the config, it decreases the size of .config from 169K
> to under 13K, losing almost every setting in the file.

Hmm ... this sound too light for a desktop kernel.  I have done the same, 
stripping out anything not relevant or wanted on my laptop's AMD kernel and 
this is what I get:

$ ls -la /usr/src/linux/.config
-rw-r--r-- 1 root root 106014 Jul 31 17:13 /usr/src/linux/.config

However, I use menuconfig almost exclusively, but this should not make any 
difference.

Did you diff the old and new .config files?  [1]


> Even stranger, if I look at "Local version - append to kernel release:"
> it still shows the value I had previously set - but that setting
> CONFIG_LOCALVERSION is NOT in .config.  If I close the tool and start
> it again, that setting is now missing and it looks like all settings
> have been reset to the clean starting defaults (i.e., many say "(NEW)"
> 
> Am I missing something here, or might this really be a bug in "make
> xconfig" ?

Have you checked the /usr/src/linux symlink is pointing to the correct kernel 
sources directory?  What you describing is akin to you working on the wrong 
.config file.


> Can anyone else replicate this?  While I don't think it's related to my
> problem getting a non-booting kernel, it certainly has me confused.
> 
> Thanks for helping me confirm what's left of my sanity.
> 
> Jack

I don't have time to replicate it this morning, but in case you're missing 
some simple step in your procedure, try this:

cd /usr/src
ls -la

check the linux symlink is pointing to the desired kernel sources directory.  
If not remove it and re-set it either manually, or by using 'eselect kernel'.

Then copy the running config to the symlinked linux directory, overwriting the 
sources' config file with its default settings.

zcat /proc/config.gz > /usr/src/linux/.config

Now you can go into the linux directory and modify its config:

cd linux
make xconfig

When you're done tweaking things make sure you save your changes before you 

make clean && make && make modules_install && make install

The last bit copies over the kernel for you to /boot if you don't want to do 
this manually or use your own naming convention.

For more details have a look here:

https://wiki.gentoo.org/wiki/Kernel/Configuration

HTH.
-- 
Regards,

Mick

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Re: [gentoo-user] kernel config strangeness

[Adam Carter]

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> However, if I start with the .config which workd, and "make xconfig"
> and select "Supported processor types" under "Processor type and
> features" and then unselect "Support Intel Pprocessors" (I have a
> Ryzen) and save the config, it decreases the size of .config from 169K
> to under 13K, losing almost every setting in the file.
>

Checking my systems, .config is 131k (AMD system, so CONFIG_CPU_SUP_INTEL
is not set) and an Intel system is 116k.

Try following the same procedure using make menuconfig instead of make
xconfig and see what happens.

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Re: [gentoo-user] kernel config strangeness

[Jack]

On 2019.08.01 22:05, Adam Carter wrote:
>> However, if I start with the .config which workd, and "make xconfig"  
>> and select "Supported processor types" under "Processor type and  
>> features" and then unselect "Support Intel Pprocessors" (I have a  
>> Ryzen) and save the config, it decreases the size of .config from  
>> 169K to under 13K, losing almost every setting in the file.
> 
> Checking my systems, .config is 131k (AMD system, so  
> CONFIG_CPU_SUP_INTEL is not set) and an Intel system is 116k.
> 
> Try following the same procedure using make menuconfig instead of  
> make xconfig and see what happens.
> 
First, I finally figured out this is not really important for me.   
"Supported Processor types" is ONLY for 32 bits.  One or more of those  
need to be set ONLY if the kernel needs to run on a 32 bit system.   
That is why it would be set for any live image which will run on 32  
bits, but would all be off for any distro that no longer supports 32  
bits.

Using menuconfig does not truncate .config.  However, my current guess  
is that some combination of settings where "Supported processor types"  
(CONFIG_PROCESSOR_SELECT) IS selected and perhaps one of it's sub  
settings (CONFIG_CPU XXX) is NOT selected causes make xconfig or  
gconfig to completely reset the configuration, reducing the next saved  
version to under 10k.

I found a (not much used) linux-config mailing list, and I'll probably  
post the issue there.

Jack

Re: [gentoo-user] kernel config strangeness

[Adam Carter]

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>
> First, I finally figured out this is not really important for me.
> "Supported Processor types" is ONLY for 32 bits.
>

When i remove Processor type and features  --->  [*] Supported processor
vendors  ---> [ ]   Support AMD processors (CONFIG_CPU_SUP_AMD) it removes
features relevant to 64 bit CPUs;

# diff .config .config-gold | grep ^\>
> CONFIG_X86_CPU_RESCTRL=y
> CONFIG_CPU_SUP_AMD=y
> # CONFIG_GART_IOMMU is not set
> CONFIG_X86_MCE_AMD=y
> CONFIG_X86_MCE_THRESHOLD=y
> CONFIG_PERF_EVENTS_AMD_POWER=y
> CONFIG_MICROCODE=y
> # CONFIG_MICROCODE_INTEL is not set
> CONFIG_MICROCODE_AMD=y
> CONFIG_MICROCODE_OLD_INTERFACE=y
> # CONFIG_AMD_MEM_ENCRYPT is not set
> CONFIG_X86_ACPI_CPUFREQ_CPB=y
> CONFIG_X86_AMD_FREQ_SENSITIVITY=y
> CONFIG_AMD_NB=y
> CONFIG_SENSORS_K10TEMP=m
> CONFIG_SENSORS_FAM15H_POWER=m
> CONFIG_AGP_AMD64=y
> CONFIG_EDAC_DECODE_MCE=y
> CONFIG_EDAC_AMD64=m
> # CONFIG_EDAC_AMD64_ERROR_INJECTION is not set

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Re: [gentoo-user] kernel config strangeness

[Jack]

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On 8/2/19 8:52 PM, Adam Carter wrote:
>
>     First, I finally figured out this is not really important for me.
>     "Supported Processor types" is ONLY for 32 bits.
>
>
> When i remove Processor type and features  --->  [*] Supported 
> processor vendors  ---> [ ]   Support AMD processors 
> (CONFIG_CPU_SUP_AMD) it removes features relevant to 64 bit CPUs;
>
> # diff .config .config-gold | grep ^\>
> > CONFIG_X86_CPU_RESCTRL=y
> > CONFIG_CPU_SUP_AMD=y
> > # CONFIG_GART_IOMMU is not set
> > CONFIG_X86_MCE_AMD=y
> > CONFIG_X86_MCE_THRESHOLD=y
> > CONFIG_PERF_EVENTS_AMD_POWER=y
> > CONFIG_MICROCODE=y
> > # CONFIG_MICROCODE_INTEL is not set
> > CONFIG_MICROCODE_AMD=y
> > CONFIG_MICROCODE_OLD_INTERFACE=y
> > # CONFIG_AMD_MEM_ENCRYPT is not set
> > CONFIG_X86_ACPI_CPUFREQ_CPB=y
> > CONFIG_X86_AMD_FREQ_SENSITIVITY=y
> > CONFIG_AMD_NB=y
> > CONFIG_SENSORS_K10TEMP=m
> > CONFIG_SENSORS_FAM15H_POWER=m
> > CONFIG_AGP_AMD64=y
> > CONFIG_EDAC_DECODE_MCE=y
> > CONFIG_EDAC_AMD64=m
> > # CONFIG_EDAC_AMD64_ERROR_INJECTION is not set

Are you sure those settings are "=y" or "=m") in the other file, and not 
just simply not present?  Changing that one setting may only have 
altered whether those other settings are explicitly included in the 
.config file, and not their value.

Jack


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Re: [gentoo-user] kernel config strangeness

[Adam Carter]

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>
> > # CONFIG_EDAC_AMD64_ERROR_INJECTION is not set
>
> Are you sure those settings are "=y" or "=m") in the other file, and not
> just simply not present?  Changing that one setting may only have altered
> whether those other settings are explicitly included in the .config file,
> and not their value.
>
On the .config that has had CONFIG_CPU_SUP_AMD removed, these settings are
no longer present.

My current understanding is that if a particular CONFIG_ option is not
present in the .config file, it will not be built due to a missing
prerequisite. Do you have a different understanding?

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