Re: [PATCH v7 4/8] crash: add phdr for possible CPUs in elfcorehdr

[Laurent Dufour <ldufour@linux.ibm.com>]

On 19/01/2023 19:29:52, Laurent Dufour wrote:
> On 15/01/2023 16:02:02, Sourabh Jain wrote:
>> On architectures like PowerPC the crash notes are available for all
>> possible CPUs. So let's populate the elfcorehdr for all possible
>> CPUs having crash notes to avoid updating elfcorehdr during in-kernel
>> crash update on CPU hotplug events.
>>
>> The similar technique is used in kexec-tool for kexec_load case.
>>
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> ---
>>  kernel/crash_core.c | 9 ++++++---
>>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> This patch is not applying on ppc/next (53ab112a9508).
> 
> As far as I could see, crash_prepare_elf64_headers() is defined in the file
> kernel/kexec_file.c and that's not recent, see babac4a84a88 (kexec_file,
> x86: move re-factored code to generic side, 2018-04-13)
> 
> Am I missing something?

My mistake, sounds that your series is based on top of the Eric's one (not yet upstream):

https://lore.kernel.org/lkml/20230118213544.2128-1-eric.devolder@oracle.com/

> 
>>
>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
>> index 910d377ea317e..19f987b3851e8 100644
>> --- a/kernel/crash_core.c
>> +++ b/kernel/crash_core.c
>> @@ -364,8 +364,8 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
>>  	ehdr->e_ehsize = sizeof(Elf64_Ehdr);
>>  	ehdr->e_phentsize = sizeof(Elf64_Phdr);
>>  
>> -	/* Prepare one phdr of type PT_NOTE for each present CPU */
>> -	for_each_present_cpu(cpu) {
>> +	/* Prepare one phdr of type PT_NOTE for possible CPU with crash note. */
>> +	for_each_possible_cpu(cpu) {
>>  #ifdef CONFIG_CRASH_HOTPLUG
>>  		if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
>>  			/* Skip the soon-to-be offlined cpu */
>> @@ -373,8 +373,11 @@ int crash_prepare_elf64_headers(struct kimage *image, struct crash_mem *mem,
>>  				continue;
>>  		}
>>  #endif
>> -		phdr->p_type = PT_NOTE;
>>  		notes_addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpu));
>> +		if (!notes_addr)
>> +			continue;
>> +
>> +		phdr->p_type = PT_NOTE;
>>  		phdr->p_offset = phdr->p_paddr = notes_addr;
>>  		phdr->p_filesz = phdr->p_memsz = sizeof(note_buf_t);
>>  		(ehdr->e_phnum)++;
>