linux-kernel - Re: [RFC][PATCH v2 01/21] e820: cheat PMEM as DRAM

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Date:   Thu, 27 Dec 2018 12:11:32 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Fan Du <fan.du@...el.com>, kvm@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Yao Yuan <yuan.yao@...el.com>,
        Peng Dong <dongx.peng@...el.com>,
        Huang Ying <ying.huang@...el.com>,
        Liu Jingqi <jingqi.liu@...el.com>,
        Dong Eddie <eddie.dong@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Zhang Yi <yi.z.zhang@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [RFC][PATCH v2 01/21] e820: cheat PMEM as DRAM

On Wed, Dec 26, 2018 at 07:41:41PM -0800, Matthew Wilcox wrote:
>On Wed, Dec 26, 2018 at 09:14:47PM +0800, Fengguang Wu wrote:
>> From: Fan Du <fan.du@...el.com>
>>
>> This is a hack to enumerate PMEM as NUMA nodes.
>> It's necessary for current BIOS that don't yet fill ACPI HMAT table.
>>
>> WARNING: take care to backup. It is mutual exclusive with libnvdimm
>> subsystem and can destroy ndctl managed namespaces.
>
>Why depend on firmware to present this "correctly"?  It seems to me like
>less effort all around to have ndctl label some namespaces as being for
>this kind of use.

Dave Hansen may be more suitable to answer your question. He posted
patches to make PMEM NUMA node coexist with libnvdimm and ndctl:

[PATCH 0/9] Allow persistent memory to be used like normal RAM
https://lkml.org/lkml/2018/10/23/9

That depends on future BIOS. So we did this quick hack to test out
PMEM NUMA node for the existing BIOS.

Thanks,
Fengguang