linux-kernel - Re: [Linux-nvdimm] [PATCH 1/2] x86: add support for the non-standard protected e820 type

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Date:	Sun, 5 Apr 2015 13:06:27 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Boaz Harrosh <boaz@...xistor.com>
Cc:	Toshi Kani <toshi.kani@...com>, Jens Axboe <axboe@...nel.dk>,
	linux-nvdimm@...1.01.org,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [Linux-nvdimm] [PATCH 1/2] x86: add support for the non-standard
 protected e820 type

On Sun, Apr 5, 2015 at 2:18 AM, Boaz Harrosh <boaz@...xistor.com> wrote:
> On 04/03/2015 08:12 PM, Yinghai Lu wrote:
>> On Fri, Apr 3, 2015 at 9:14 AM, Toshi Kani <toshi.kani@...com> wrote:
>>> On Wed, 2015-04-01 at 09:12 +0200, Christoph Hellwig wrote:
>>>   :
>>>> @@ -748,7 +758,7 @@ u64 __init early_reserve_e820(u64 size, u64 align)
>>>>  /*
>>>>   * Find the highest page frame number we have available
>>>>   */
>>>> -static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
>>>> +static unsigned long __init e820_end_pfn(unsigned long limit_pfn)
>>>>  {
>>>>       int i;
>>>>       unsigned long last_pfn = 0;
>>>> @@ -759,7 +769,11 @@ static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
>>>>               unsigned long start_pfn;
>>>>               unsigned long end_pfn;
>>>>
>>>> -             if (ei->type != type)
>>>> +             /*
>>>> +              * Persistent memory is accounted as ram for purposes of
>>>> +              * establishing max_pfn and mem_map.
>>>> +              */
>>>> +             if (ei->type != E820_RAM && ei->type != E820_PRAM)
>>>>                       continue;
>>>
>>> Should we also delete this code, accounting E820_PRAM as ram, along with
>>> the deletion of reserve_pmem() in this version?
>>
>
> Hi Yinghai, Toshi
>
> In my old patches I did not have these updates as well, and everything
> was very much usable, for a long time.
>
> However. I actually liked these changes in Christoph's patches and
> thought they should stay, here is why.
>
> Today I will be sending patches to make pmem be supported with
> page-struct as an optional alternative to the use of ioremap.
> This is for advanced users that wants to RDMA direct_IO and so
> on directly out of pmem.

but it is not related.  Should just remove those lines.

And even his original changes about memblock is not needed.

| You did not modify memblock_x86_fill() to treat
| E820_PRAM as E820_RAM, so memblock will not have any
| entry for E820_PRAM, so you do not need to call memblock_reserve
| there.
|
| And the same time, init_memory_mapping() will call
| init_range_memory_mapping/for_each_mem_pfn_range() to
| set kernel mapping for memory range in memblock only.
| So here calling init_memory_mapping will not do anything.
| then just drop calling to that init_memory_mapping.
| --- so will not kernel mapping pmem, is that what you intended to have?
|
| After those two changes, You do not need this reserve_pmem at all.
| Just drop it.
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