linux-kernel - Re: [PATCH] s390/crash: Fix KEXEC_NOTE

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Message-ID: <593D02AB.1030706@redhat.com>
Date:   Sun, 11 Jun 2017 16:43:23 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Dave Young <dyoung@...hat.com>, Xunlei Pang <xlpang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        akpm@...ux-foundation.org, Eric Biederman <ebiederm@...ssion.com>,
        Baoquan He <bhe@...hat.com>,
        Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, Dave Anderson <anderson@...hat.com>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        Gustavo Luiz Duarte <gustavold@...ux.vnet.ibm.com>
Subject: Re: [PATCH] s390/crash: Fix KEXEC_NOTE_BYTES definition

On 06/09/2017 at 03:45 PM, Dave Young wrote:
> On 06/09/17 at 10:29am, Dave Young wrote:
>> On 06/09/17 at 10:17am, Xunlei Pang wrote:
>>> S390 KEXEC_NOTE_BYTES is not used by note_buf_t as before, which
>>> is now defined as follows:
>>>     typedef u32 note_buf_t[CRASH_CORE_NOTE_BYTES/4];
>>> It was changed by the CONFIG_CRASH_CORE feature.
>>>
>>> This patch gets rid of all the old KEXEC_NOTE_BYTES stuff, and
>>> renames KEXEC_NOTE_BYTES to CRASH_CORE_NOTE_BYTES for S390.
>>>
>>> Fixes: 692f66f26a4c ("crash: move crashkernel parsing and vmcore related code under CONFIG_CRASH_CORE")
>>> Cc: Dave Young <dyoung@...hat.com>
>>> Cc: Dave Anderson <anderson@...hat.com>
>>> Cc: Hari Bathini <hbathini@...ux.vnet.ibm.com>
>>> Cc: Gustavo Luiz Duarte <gustavold@...ux.vnet.ibm.com>
>>> Signed-off-by: Xunlei Pang <xlpang@...hat.com>
>>> ---
>>>  arch/s390/include/asm/kexec.h |  2 +-
>>>  include/linux/crash_core.h    |  7 +++++++
>>>  include/linux/kexec.h         | 11 +----------
>>>  3 files changed, 9 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/arch/s390/include/asm/kexec.h b/arch/s390/include/asm/kexec.h
>>> index 2f924bc..352deb8 100644
>>> --- a/arch/s390/include/asm/kexec.h
>>> +++ b/arch/s390/include/asm/kexec.h
>>> @@ -47,7 +47,7 @@
>>>   * Seven notes plus zero note at the end: prstatus, fpregset, timer,
>>>   * tod_cmp, tod_reg, control regs, and prefix
>>>   */
>>> -#define KEXEC_NOTE_BYTES \
>>> +#define CRASH_CORE_NOTE_BYTES \
>>>  	(ALIGN(sizeof(struct elf_note), 4) * 8 + \
>>>  	 ALIGN(sizeof("CORE"), 4) * 7 + \
>>>  	 ALIGN(sizeof(struct elf_prstatus), 4) + \
> I found that in mainline since below commit, above define should be
> useless, but if distribution with older kernel does need your fix, so in
> mainline the right fix should be dropping the s390 part about these
> macros usage.

Indeed, then I think we can remove this special definition of S390 to avoid confusion.

Regards,
Xunlei

>
> Anyway this need a comment from Michael.
>
> commit 8a07dd02d7615d91d65d6235f7232e3f9b5d347f
> Author: Martin Schwidefsky <schwidefsky@...ibm.com>
> Date:   Wed Oct 14 15:53:06 2015 +0200
>
>     s390/kdump: remove code to create ELF notes in the crashed system
>     
>     The s390 architecture can store the CPU registers of the crashed
> system
>     after the kdump kernel has been started and this is the preferred
> way.
>     Remove the remaining code fragments that deal with storing CPU
> registers
>     while the crashed system is still active.
>     
>     Acked-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
>     Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
>
>
>>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>>> index e9de6b4..dbc6e5c 100644
>>> --- a/include/linux/crash_core.h
>>> +++ b/include/linux/crash_core.h
>>> @@ -10,9 +10,16 @@
>>>  #define CRASH_CORE_NOTE_NAME_BYTES ALIGN(sizeof(CRASH_CORE_NOTE_NAME), 4)
>>>  #define CRASH_CORE_NOTE_DESC_BYTES ALIGN(sizeof(struct elf_prstatus), 4)
>>>  
>>> +/*
>>> + * The per-cpu notes area is a list of notes terminated by a "NULL"
>>> + * note header.  For kdump, the code in vmcore.c runs in the context
>>> + * of the second kernel to combine them into one note.
>>> + */
>>> +#ifndef CRASH_CORE_NOTE_BYTES
>>>  #define CRASH_CORE_NOTE_BYTES	   ((CRASH_CORE_NOTE_HEAD_BYTES * 2) +	\
>>>  				     CRASH_CORE_NOTE_NAME_BYTES +	\
>>>  				     CRASH_CORE_NOTE_DESC_BYTES)
>>> +#endif
>>>  
>>>  #define VMCOREINFO_BYTES	   PAGE_SIZE
>>>  #define VMCOREINFO_NOTE_NAME	   "VMCOREINFO"
>>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>>> index 3ea8275..133df03 100644
>>> --- a/include/linux/kexec.h
>>> +++ b/include/linux/kexec.h
>>> @@ -14,7 +14,6 @@
>>>  
>>>  #if !defined(__ASSEMBLY__)
>>>  
>>> -#include <linux/crash_core.h>
>>>  #include <asm/io.h>
>>>  
>>>  #include <uapi/linux/kexec.h>
>>> @@ -25,6 +24,7 @@
>>>  #include <linux/ioport.h>
>>>  #include <linux/module.h>
>>>  #include <asm/kexec.h>
>>> +#include <linux/crash_core.h>
>>>  
>>>  /* Verify architecture specific macros are defined */
>>>  
>>> @@ -63,15 +63,6 @@
>>>  #define KEXEC_CORE_NOTE_NAME	CRASH_CORE_NOTE_NAME
>>>  
>>>  /*
>>> - * The per-cpu notes area is a list of notes terminated by a "NULL"
>>> - * note header.  For kdump, the code in vmcore.c runs in the context
>>> - * of the second kernel to combine them into one note.
>>> - */
>>> -#ifndef KEXEC_NOTE_BYTES
>>> -#define KEXEC_NOTE_BYTES	CRASH_CORE_NOTE_BYTES
>>> -#endif
>> It is still not clear how does s390 use the crash_notes except this macro.
>> But from code point of view we do need to update this as well after the
>> crash_core splitting.
>>
>> Acked-by: Dave Young <dyoung@...hat.com>
> Hold on the ack because of the new findings, wait for Michael's
> feedback.
>
> Thanks
> Dave