[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <a2e0b554-2ef4-1266-cc3a-fa5a28049131@linux.ibm.com>
Date: Tue, 4 Oct 2022 12:33:24 +0530
From: Sourabh Jain <sourabhjain@...ux.ibm.com>
To: Eric DeVolder <eric.devolder@...cle.com>,
Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
kexec@...ts.infradead.org, ebiederm@...ssion.com,
dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com,
tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
hpa@...or.com, nramas@...ux.microsoft.com, thomas.lendacky@....com,
robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
konrad.wilk@...cle.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support
On 30/09/22 21:06, Eric DeVolder wrote:
>
>
> On 9/28/22 11:07, Borislav Petkov wrote:
>> On Tue, Sep 13, 2022 at 02:12:31PM -0500, Eric DeVolder wrote:
>>> This topic was discussed previously https://lkml.org/lkml/2022/3/3/372.
>>
>> Please do not use lkml.org to refer to lkml messages. We have a
>> perfectly fine archival system at lore.kernel.org. You simply do
>>
>> https://lore.kernel.org/r/<Message-ID>
>>
>> when you want to point to a previous mail.
>
> ok, thanks for pointing that out to me.
>>
>>> David points out that terminology is tricky here due to differing
>>> behaviors.
>>> And perhaps that is your point in asking for guidance text. It can be
>>> complicated
>>
>> Which means you need an explanation how to use this even more.
>>
>> And why is CONFIG_CRASH_MAX_MEMORY_RANGES even a Kconfig item and not
>> something you discover from the hardware?
>
> No, is the short answer.
>
>>
>> Your help text talks about System RAM entries in /proc/iomem which means
>> that those entries are present somewhere in the kernel and you can read
>> them out and do the proper calculations dynamically instead of doing the
>> static CONFIG_NR_CPUS_DEFAULT + CONFIG_CRASH_MAX_MEMORY_RANGES thing.
>
> The intent is to compute the max size buffer needed to contain a
> maximum populated elfcorehdr, which is primarily based on the number
> of CPUs and memory regions. Thus far I (and others involved) have not
> found a kernel method to determine the maximum number of memory
> regions possible (if you are aware of one, please let me know!). Thus
> CONFIG_CRASH_MAX_MEMORY_RANGES was born (rather borrowed from
> kexec-tools).
>
> So no dynamic computation is possible, yet.
Hello Eric,
How about allocating buffer space for max program header possible in a
elfcorehdr?
mage->elf_headers_sz = kbuf.memsz = PN_XNUM * sizeof(Elf64_Phdr);
PN_XNUM is part of linux/elf.h (include/uapi/linux/elf.h).
Refer below link for more details:
https://man7.org/linux/man-pages/man5/elf.5.html
Thanks,
Sourabh Jain
Powered by blists - more mailing lists