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

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Message-ID: <58860406.1030604@redhat.com>
Date:   Mon, 23 Jan 2017 21:24:22 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Dave Young <dyoung@...hat.com>, Xunlei Pang <xlpang@...hat.com>
Cc:     Baoquan He <bhe@...hat.com>, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Robert LeBlanc <robert@...lancnet.us>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] x86/crash: Update the stale comment in
 reserve_crashkernel()

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@...lancnet.us>
>> Cc: Baoquan He <bhe@...hat.com>
>> Signed-off-by: Xunlei Pang <xlpang@...hat.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
>
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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