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Date:   Thu, 7 Oct 2021 11:02:11 +0200
From:   Oscar Salvador <osalvador@suse.de>
To:     David Hildenbrand <david@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Jonathan Corbet <corbet@lwn.net>, Alex Shi <alexs@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Shuah Khan <shuah@kernel.org>, Michal Hocko <mhocko@suse.com>,
        Mike Rapoport <rppt@kernel.org>, x86@kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v1 3/6] mm/memory_hotplug: restrict CONFIG_MEMORY_HOTPLUG
 to 64 bit
Message-ID: <YV63kyvrxt0tx/Ru@localhost.localdomain>
References: <20210929143600.49379-1-david@redhat.com>
 <20210929143600.49379-4-david@redhat.com>
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On Wed, Sep 29, 2021 at 04:35:57PM +0200, David Hildenbrand wrote:
> 32 bit support is broken in various ways: for example, we can online
> memory that should actually go to ZONE_HIGHMEM to ZONE_MOVABLE or in
> some cases even to one of the other kernel zones.
> 
> We marked it BROKEN in commit b59d02ed0869 ("mm/memory_hotplug: disable the
> functionality for 32b") almost one year ago. According to that commit
> it might be broken at least since 2017. Further, there is hardly a sane use
> case nowadays.
> 
> Let's just depend completely on 64bit, dropping the "BROKEN" dependency to
> make clear that we are not going to support it again. Next, we'll remove
> some HIGHMEM leftovers from memory hotplug code to clean up.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
>  mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index ea8762cd8e1e..88273dd5c6d6 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -125,7 +125,7 @@ config MEMORY_HOTPLUG
>  	select MEMORY_ISOLATION
>  	depends on SPARSEMEM
>  	depends on ARCH_ENABLE_MEMORY_HOTPLUG
> -	depends on 64BIT || BROKEN
> +	depends on 64BIT
>  	select NUMA_KEEP_MEMINFO if NUMA
>  
>  config MEMORY_HOTPLUG_DEFAULT_ONLINE
> -- 
> 2.31.1
> 
> 

-- 
Oscar Salvador
SUSE Labs