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

From: Dave Young
Date: Fri Mar 09 2012 - 23:34:36 EST


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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/