Re: [PATCH 2/3] automation: Change build script to use arch defconfig

[Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>]

On 9/26/23 12:43 PM, Shawn Anastasio wrote:
> On 9/26/23 2:19 AM, Jan Beulich wrote:
>> On 26.09.2023 01:12, Stefano Stabellini wrote:
>>> On Mon, 25 Sep 2023, Shawn Anastasio wrote:
>>>> Change automation build script to call the make defconfig target before
>>>> setting CONFIG_DEBUG and extra options. This fixes issues on Power where
>>>> the build fails without using the ppc64_defconfig.
>>>>
>>>> Signed-off-by: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
>>>> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> Nit: Tags in chronological order please (also affects patch 1).
>>
> Will fix.
> 
>>> What is the problem specifically? Is the issue that CONFIG_DEBUG enabled
>>> before make olddefconfig causes certain DEBUG options also to default to
>>> yes, and these additional options don't work well on Power?
>>
>> No, the issue is that "make olddefconfig" takes the existing .config
>> without even considering the arch's default configuration that was
>> specified (KBUILD_DEFCONFIG).
>>
>>>> --- a/automation/scripts/build
>>>> +++ b/automation/scripts/build
>>>> @@ -22,7 +22,12 @@ if [[ "${RANDCONFIG}" == "y" ]]; then
>>>>      # RANDCONFIG implies HYPERVISOR_ONLY
>>>>      HYPERVISOR_ONLY="y"
>>>>  else
>>>> -    echo "CONFIG_DEBUG=${debug}" > xen/.config
>>>> +    # Start off with arch's defconfig
>>>> +    make -C xen defconfig
>>>> +
>>>> +    # Drop existing CONFIG_DEBUG and replace with value of ${debug}
>>>> +    sed -i 's/^CONFIG_DEBUG=[yn]//g' xen/.config
>>>> +    echo "CONFIG_DEBUG=${debug}" >> xen/.config
>>>>
>>>>      if [[ -n "${EXTRA_XEN_CONFIG}" ]]; then
>>>>          echo "${EXTRA_XEN_CONFIG}" >> xen/.config
>>
>> It never really became clear to me whether kconfig honors the first,
>> last, or any random setting in a .config that it takes as input, when
>> a certain option appears there more than once. The change you make
>> implies it's consistently "last" - can you confirm that's the actual
>> behavior of kconfig?
>>
> 
> I actually tried to avoid this issue alltogether with the sed command I
> added before the echo to drop any existing CONFIG_DEBUG= line.
>

Just realized that options in $EXTRA_XEN_CONFIG would also be subject to
this which is likely what you meant to point out -- my apologies.

I've tested locally and Kconfig does indeed seem to honor the last
setting. It throws some warnings about the overridden symbol but the
build continues with the latest value, e.g:

.config:94:warning: override: reassigning to symbol DEBUG
.config:95:warning: override: reassigning to symbol DEBUG

Thanks,
Shawn