linux-kernel - Re: [RFC PATCH 1/3] mm,memory_hotplug: Introduce MHP_MEMMAP_ON

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Message-ID: <8cf48839-1813-8992-ad87-f0fd195ab107@redhat.com>
Date:   Thu, 22 Oct 2020 15:04:00 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     mhocko@...nel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, vbabka@...e.cz, pasha.tatashin@...een.com
Subject: Re: [RFC PATCH 1/3] mm,memory_hotplug: Introduce MHP_MEMMAP_ON_MEMORY

On 22.10.20 14:58, Oscar Salvador wrote:
> MHP_MEMMAP_ON_MEMORY tells the system that we want the memmap
> pagetables to be built from the hot-added range.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> ---
>  include/linux/memory_hotplug.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index d65c6fdc5cfc..dda2d0e5d1ba 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -70,6 +70,14 @@ typedef int __bitwise mhp_t;
>   */
>  #define MEMHP_MERGE_RESOURCE	((__force mhp_t)BIT(0))

BTW, I messed that one up, I already have a patch lying around here
to tun that properly into "MHP_MERGE_RESOURCE"

>  
> +/*
> + * We want memmap (struct page array) to be self contained.
> + * To do so, we will use the beginning of the hot-added range to build
> + * the page tables for the memmap array that describes the entire range.
> + * Only selected architectures support it with SPARSE_VMEMMAP.
> + */
> +#define MEMHP_MEMMAP_ON_MEMORY	((__force mhp_t)BIT(1))

So this should be MHP_MEMMAP_ON_MEMORY.

-- 
Thanks,

David / dhildenb