linux-kernel - Re: [RFC PATCH] Memory hotplug support for arm64 platform

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Date:   Thu, 15 Dec 2016 14:40:05 +0800
From:   Xishi Qiu <qiuxishi@...wei.com>
To:     Maciej Bielski <m.bielski@...tualopensystems.com>
CC:     <scott.branden@...adcom.com>, <will.deacon@....com>,
        <ar@...ux.vnet.ibm.com>, <tech@...tualopensystems.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] Memory hotplug support for arm64 platform

On 2016/12/15 14:18, Xishi Qiu wrote:

> On 2016/12/14 20:16, Maciej Bielski wrote:
> 
>>
>>  
>> -#ifdef CONFIG_MEMORY_HOTREMOVE
>> -int arch_remove_memory(u64 start, u64 size)
>> -{
>> -	unsigned long start_pfn = start >> PAGE_SHIFT;
>> -	unsigned long nr_pages = size >> PAGE_SHIFT;
>> -	struct zone *zone;
>> -	int ret;
>> +		SetPageReserved(pfn_to_page(pfn));
>> +	}
> 
> Hi Maciej,
> 
> Why we need to set reserved here?
> I think the new pages are already reserved in __add_zone() -> memmap_init_zone(), right?
> 

Hi Maciej,

The reason is as follows, right?

It's because that in memmap_init_zone() -> early_pfn_valid(), the new page is still
invalid, so we need to init it after memblock_clear_nomap()

So why not use __init_single_page() and set_pageblock_migratetype()?

> Thanks,
> Xishi Qiu
>