linux-kernel - Re: [PATCH] kdump x86: fix total mem size calculation for reservation

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Date:	Sat, 10 Mar 2012 12:32:28 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux@....linux.org.uk, vgoyal@...hat.com
Subject: Re: [PATCH] kdump x86: fix total mem size calculation for reservation

On 03/10/2012 11:27 AM, Cong Wang wrote:

> On 03/09/2012 04:30 PM, Dave Young wrote:
>> crashkernel reservation need know the total memory size. Current
>> get_total_mem
>> simply use max_pfn - min_low_pfn. It is wrong because it will including
>> memory holes in the middle.
>>
>> Especially for kvm guest with memory>  0xe0000000, there's below in
>> qemu code:
>> qemu split memory as below:
>>      if (ram_size>= 0xe0000000 ) {
>>          above_4g_mem_size = ram_size - 0xe0000000;
>>          below_4g_mem_size = 0xe0000000;
>>      } else {
>>          below_4g_mem_size = ram_size;
>>      }
>> So for 4G mem guest, seabios will insert a 512M usable region beyond
>> of 4G.
>> Thus in above case max_pfn - min_low_pfn will be more than original
>> memsize.
>>
>> Fixing this issue by using memblock_phys_mem_size() to get the total
>> memsize.
>>
> 
> Makes sense for me!
> 
>> -static inline unsigned long long get_total_mem(void)
>> -{
>> -    unsigned long long total;
>> -
>> -    total = max_pfn - min_low_pfn;
>> -    printk("hidave: memsize=%llu\n", memblock_phys_mem_size());
> 
> This debugging line does not exist... so this patch can't be applied.


Yes, good catch, will remove the line and resend.


-- 
Thanks
Dave
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