linux-kernel - Re: [PATCH v3 12/13] s390/kexec: refactor for kernel/Kconfig.kexec

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Message-ID: <c4552463-a6b8-2c4f-a091-d7a6558c8236@oracle.com>
Date:   Fri, 30 Jun 2023 09:33:39 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>
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Subject: Re: [PATCH v3 12/13] s390/kexec: refactor for kernel/Kconfig.kexec



On 6/30/23 08:07, Alexander Gordeev wrote:
> On Mon, Jun 26, 2023 at 12:13:31PM -0400, Eric DeVolder wrote:
>> The kexec and crash kernel options are provided in the common
>> kernel/Kconfig.kexec. Utilize the common options and provide
>> the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
>> equivalent set of KEXEC and CRASH options.
>>
>> NOTE: The original Kconfig has a KEXEC_SIG which depends on
>> MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
>> dependency (using the strategy outlined in this series, and other
>> techniques) results in 'error: recursive dependency detected'
>> on CRYPTO.
>>
>> Per Alexander Gordeev <agordeev@...ux.ibm.com>: "the MODULE_SIG_FORMAT
>> dependency was introduced with [git commit below] and in fact was not
>> necessary, since s390 did/does not use mod_check_sig() anyway.
>>
>>   commit c8424e776b09 ("MODSIGN: Export module signature definitions")
>>
>> MODULE_SIG_FORMAT is needed to select SYSTEM_DATA_VERIFICATION. But
>> SYSTEM_DATA_VERIFICATION is also selected by FS_VERITY*, so dropping
>> MODULE_SIG_FORMAT does not hurt."
>>
>> Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
>> from KEXEC_SIG. Still results in equivalent .config files for s390.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
>> ---
>>   arch/s390/Kconfig | 65 ++++++++++++++---------------------------------
>>   1 file changed, 19 insertions(+), 46 deletions(-)
>>
>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>> index 6dab9c1be508..58dc124433ca 100644
>> --- a/arch/s390/Kconfig
>> +++ b/arch/s390/Kconfig
>> @@ -243,6 +243,25 @@ config PGTABLE_LEVELS
>>   
>>   source "kernel/livepatch/Kconfig"
>>   
>> +config ARCH_DEFAULT_KEXEC
>> +	def_bool y
>> +
>> +config ARCH_SUPPORTS_KEXEC
>> +	def_bool y
>> +
>> +config ARCH_SUPPORTS_KEXEC_FILE
>> +	def_bool CRYPTO && CRYPTO_SHA256 && CRYPTO_SHA256_S390
>> +
>> +config ARCH_HAS_KEXEC_PURGATORY
>> +	def_bool KEXEC_FILE
>> +
>> +config ARCH_SUPPORTS_CRASH_DUMP
>> +	def_bool y
>> +	help
>> +	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
>> +	  This option also enables s390 zfcpdump.
>> +	  See also <file:Documentation/s390/zfcpdump.rst>
>> +
>>   menu "Processor type and features"
>>   
>>   config HAVE_MARCH_Z10_FEATURES
>> @@ -481,36 +500,6 @@ config SCHED_TOPOLOGY
>>   
>>   source "kernel/Kconfig.hz"
>>   
>> -config KEXEC
>> -	def_bool y
>> -	select KEXEC_CORE
>> -
>> -config KEXEC_FILE
>> -	bool "kexec file based system call"
>> -	select KEXEC_CORE
>> -	depends on CRYPTO
>> -	depends on CRYPTO_SHA256
>> -	depends on CRYPTO_SHA256_S390
>> -	help
>> -	  Enable the kexec file based system call. In contrast to the normal
>> -	  kexec system call this system call takes file descriptors for the
>> -	  kernel and initramfs as arguments.
>> -
>> -config ARCH_HAS_KEXEC_PURGATORY
>> -	def_bool y
>> -	depends on KEXEC_FILE
>> -
>> -config KEXEC_SIG
>> -	bool "Verify kernel signature during kexec_file_load() syscall"
>> -	depends on KEXEC_FILE && MODULE_SIG_FORMAT
>> -	help
>> -	  This option makes kernel signature verification mandatory for
>> -	  the kexec_file_load() syscall.
>> -
>> -	  In addition to that option, you need to enable signature
>> -	  verification for the corresponding kernel image type being
>> -	  loaded in order for this to work.
>> -
>>   config KERNEL_NOBP
>>   	def_bool n
>>   	prompt "Enable modified branch prediction for the kernel by default"
>> @@ -732,22 +721,6 @@ config VFIO_AP
>>   
>>   endmenu
>>   
>> -menu "Dump support"
>> -
>> -config CRASH_DUMP
>> -	bool "kernel crash dumps"
>> -	select KEXEC
>> -	help
>> -	  Generate crash dump after being started by kexec.
>> -	  Crash dump kernels are loaded in the main kernel with kexec-tools
>> -	  into a specially reserved region and then later executed after
>> -	  a crash by kdump/kexec.
>> -	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
>> -	  This option also enables s390 zfcpdump.
>> -	  See also <file:Documentation/s390/zfcpdump.rst>
>> -
>> -endmenu
>> -
>>   config CCW
>>   	def_bool y
> 
> Acked-by: Alexander Gordeev <agordeev@...ux.ibm.com>

Thank you Alexander!
eric