[PATCH v2] x86/crash: Update the stale comment in reserve_crashkernel()

[PATCH v2] x86/crash: Update the stale comment in reserve_crashkernel()

[Xunlei Pang]

CRASH_KERNEL_ADDR_MAX has been missing for a long time,
update it with more detailed explanation.

Cc: Robert LeBlanc <robert@leblancnet.us>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
 arch/x86/kernel/setup.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4cfba94..c32a167 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
 	/* 0 means: find the address automatically */
 	if (crash_base <= 0) {
 		/*
-		 *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
+		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
+		 * as old kexec-tools loads bzImage below that, unless
+		 * "crashkernel=size[KMG],high" is specified.
 		 */
 		crash_base = memblock_find_in_range(CRASH_ALIGN,
 						    high ? CRASH_ADDR_HIGH_MAX
-- 
1.8.3.1

[tip:x86/debug] x86/crash: Update the stale comment in reserve_crashkernel()

[tip-bot for Xunlei Pang]

Commit-ID:  a8d4c8246b290ce97f88752d833804843041ac84
Gitweb:     http://git.kernel.org/tip/a8d4c8246b290ce97f88752d833804843041ac84
Author:     Xunlei Pang <xlpang@redhat.com>
AuthorDate: Mon, 23 Jan 2017 14:48:23 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 23 Jan 2017 08:57:55 +0100

x86/crash: Update the stale comment in reserve_crashkernel()

CRASH_KERNEL_ADDR_MAX has been missing for a long time,
update it with a more detailed explanation.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Young <dyoung@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert LeBlanc <robert@leblancnet.us>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/1485154103-18426-1-git-send-email-xlpang@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/setup.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 4cfba94..eb69b14 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
 	/* 0 means: find the address automatically */
 	if (crash_base <= 0) {
 		/*
-		 *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
+		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory,
+		 * as old kexec-tools loads bzImage below that, unless
+		 * "crashkernel=size[KMG],high" is specified.
 		 */
 		crash_base = memblock_find_in_range(CRASH_ALIGN,
 						    high ? CRASH_ADDR_HIGH_MAX

Re: [PATCH v2] x86/crash: Update the stale comment in reserve_crashkernel()

[Dave Young]

Hi, Xunlei

On 01/23/17 at 02:48pm, Xunlei Pang wrote:
> CRASH_KERNEL_ADDR_MAX has been missing for a long time,
> update it with more detailed explanation.
> 
> Cc: Robert LeBlanc <robert@leblancnet.us>
> Cc: Baoquan He <bhe@redhat.com>
> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
> ---
>  arch/x86/kernel/setup.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 4cfba94..c32a167 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
>  	/* 0 means: find the address automatically */
>  	if (crash_base <= 0) {
>  		/*
> -		 *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
> +		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
> +		 * as old kexec-tools loads bzImage below that, unless
> +		 * "crashkernel=size[KMG],high" is specified.

There is already comment before the define of those macros, also
there are 32bit case which has a different reason about 512M there as
well.

So it looks better to just drop the one line comment without adding
further comments here.
>  		 */
>  		crash_base = memblock_find_in_range(CRASH_ALIGN,
>  						    high ? CRASH_ADDR_HIGH_MAX
> -- 
> 1.8.3.1
> 

Thanks
Dave

Re: [PATCH v2] x86/crash: Update the stale comment in reserve_crashkernel()

[Xunlei Pang]

On 01/23/2017 at 04:48 PM, Dave Young wrote:
> Hi, Xunlei
>
> On 01/23/17 at 02:48pm, Xunlei Pang wrote:
>> CRASH_KERNEL_ADDR_MAX has been missing for a long time,
>> update it with more detailed explanation.
>>
>> Cc: Robert LeBlanc <robert@leblancnet.us>
>> Cc: Baoquan He <bhe@redhat.com>
>> Signed-off-by: Xunlei Pang <xlpang@redhat.com>
>> ---
>>  arch/x86/kernel/setup.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 4cfba94..c32a167 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -575,7 +575,9 @@ static void __init reserve_crashkernel(void)
>>  	/* 0 means: find the address automatically */
>>  	if (crash_base <= 0) {
>>  		/*
>> -		 *  kexec want bzImage is below CRASH_KERNEL_ADDR_MAX
>> +		 * Set CRASH_ADDR_LOW_MAX upper bound for crash memory
>> +		 * as old kexec-tools loads bzImage below that, unless
>> +		 * "crashkernel=size[KMG],high" is specified.
> There is already comment before the define of those macros, also
> there are 32bit case which has a different reason about 512M there as
> well.

If we see from the kexec's perspective, we have a common CRASH_ADDR_LOW_MAX
definition for both x86 32-bit and 64-bit(32-bit x86 has the same value defined for
CRASH_ADDR_LOW_MAX and CRASH_ADDR_HIGH_MAX), so old kexec will load below
CRASH_ADDR_LOW_MAX,  so I think the description is fine :-)

Regards,
Xunlei

>
> So it looks better to just drop the one line comment without adding
> further comments here.
>>  		 */
>>  		crash_base = memblock_find_in_range(CRASH_ALIGN,
>>  						    high ? CRASH_ADDR_HIGH_MAX
>> -- 
>> 1.8.3.1
>>
> Thanks
> Dave
>
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> kexec mailing list
> kexec@lists.infradead.org
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