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Date:   Thu, 7 Oct 2021 11:15:58 +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 6/6] x86: remove memory hotplug support on X86_32
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References: <20210929143600.49379-1-david@redhat.com>
 <20210929143600.49379-7-david@redhat.com>
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On Wed, Sep 29, 2021 at 04:36:00PM +0200, David Hildenbrand wrote:
> CONFIG_MEMORY_HOTPLUG was marked BROKEN over one year and we just
> restricted it to 64 bit. Let's remove the unused x86 32bit implementation
> and simplify the Kconfig.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

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

> ---
>  arch/x86/Kconfig      |  6 +++---
>  arch/x86/mm/init_32.c | 31 -------------------------------
>  2 files changed, 3 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ab83c22d274e..85f4762429f1 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -62,7 +62,7 @@ config X86
>  	select ARCH_32BIT_OFF_T			if X86_32
>  	select ARCH_CLOCKSOURCE_INIT
>  	select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
> -	select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
> +	select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64
>  	select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG
>  	select ARCH_ENABLE_SPLIT_PMD_PTLOCK if (PGTABLE_LEVELS > 2) && (X86_64 || X86_PAE)
>  	select ARCH_ENABLE_THP_MIGRATION if X86_64 && TRANSPARENT_HUGEPAGE
> @@ -1615,7 +1615,7 @@ config ARCH_SELECT_MEMORY_MODEL
>  
>  config ARCH_MEMORY_PROBE
>  	bool "Enable sysfs memory/probe interface"
> -	depends on X86_64 && MEMORY_HOTPLUG
> +	depends on MEMORY_HOTPLUG
>  	help
>  	  This option enables a sysfs memory/probe interface for testing.
>  	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
> @@ -2395,7 +2395,7 @@ endmenu
>  
>  config ARCH_HAS_ADD_PAGES
>  	def_bool y
> -	depends on X86_64 && ARCH_ENABLE_MEMORY_HOTPLUG
> +	depends on ARCH_ENABLE_MEMORY_HOTPLUG
>  
>  config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
>  	def_bool y
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index bd90b8fe81e4..5cd7ea6d645c 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -779,37 +779,6 @@ void __init mem_init(void)
>  	test_wp_bit();
>  }
>  
> -#ifdef CONFIG_MEMORY_HOTPLUG
> -int arch_add_memory(int nid, u64 start, u64 size,
> -		    struct mhp_params *params)
> -{
> -	unsigned long start_pfn = start >> PAGE_SHIFT;
> -	unsigned long nr_pages = size >> PAGE_SHIFT;
> -	int ret;
> -
> -	/*
> -	 * The page tables were already mapped at boot so if the caller
> -	 * requests a different mapping type then we must change all the
> -	 * pages with __set_memory_prot().
> -	 */
> -	if (params->pgprot.pgprot != PAGE_KERNEL.pgprot) {
> -		ret = __set_memory_prot(start, nr_pages, params->pgprot);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	return __add_pages(nid, start_pfn, nr_pages, params);
> -}
> -
> -void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> -{
> -	unsigned long start_pfn = start >> PAGE_SHIFT;
> -	unsigned long nr_pages = size >> PAGE_SHIFT;
> -
> -	__remove_pages(start_pfn, nr_pages, altmap);
> -}
> -#endif
> -
>  int kernel_set_to_readonly __read_mostly;
>  
>  static void mark_nxdata_nx(void)
> -- 
> 2.31.1
> 
> 

-- 
Oscar Salvador
SUSE Labs