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Subject: Re: [PATCH RFC 2/2] mm/memory_hotplug: handle memblocks only with
 CONFIG_ARCH_KEEP_MEMBLOCK
To:     Michal Hocko <mhocko@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Baoquan He <bhe@redhat.com>,
        Oscar Salvador <osalvador@suse.de>,
        Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>
References: <20200416104707.20219-1-david@redhat.com>
 <20200416104707.20219-3-david@redhat.com>
 <20200421123953.GF27314@dhcp22.suse.cz>
From:   David Hildenbrand <david@redhat.com>
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Date:   Tue, 21 Apr 2020 14:41:41 +0200
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>> For s390x, it seems to be fairly easy to avoid CONFIG_ARCH_KEEP_MEMBLOCK.
>> arm64 could rework most code (esp., pfn_valid(), valid_phys_addr_range()
>> and kexec_file_load()) to not require memblocks for hotplugged
>> memory. E.g., as hotplugged memory has no holes and can be identified
>> using !early_section(), arm64's variant of pfn_valid() could be reworked
>> fairly easily to not require memblocks for hotadded memory. powerpc might
>> be more involed.
> 
> I haven't checked these architectures but is the information really
> useful for this patch?

It might of interest for Arm64 people (cced below). I sent out s390x
patches to change that.

I can drop that part.

> 
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Baoquan He <bhe@redhat.com>
>> Cc: Oscar Salvador <osalvador@suse.de>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Mike Rapoport <rppt@linux.ibm.com>
>> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> Acked-by: Michal Hocko <mhocko@suse.com>
> 
> with a minor nit
> 
>> -	/*
>> -	 * Add new range to memblock so that when hotadd_new_pgdat() is called
>> -	 * to allocate new pgdat, get_pfn_range_for_nid() will be able to find
>> -	 * this new range and calculate total pages correctly.  The range will
>> -	 * be removed at hot-remove time.
>> -	 */
>> +#ifdef CONFIG_ARCH_KEEP_MEMBLOCK
> 
> 	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)
> 
> would be slightly nicer. This should work for all the ifedefs in this
> patch.

Yeah, will change if it compiles.


-- 
Thanks,

David / dhildenb