linux-kernel - Re: [RFC V2 0/3] mm/hotplug: Pre-validate the address range with platform

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Message-ID: <2d2a947f-3c4f-6106-583a-7da4e757a7aa@arm.com>
Date:   Thu, 3 Dec 2020 05:42:35 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, david@...hat.com,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC V2 0/3] mm/hotplug: Pre-validate the address range with
 platform



On 12/3/20 2:05 AM, Heiko Carstens wrote:
> On Mon, Nov 30, 2020 at 08:59:49AM +0530, Anshuman Khandual wrote:
>> This series adds a mechanism allowing platforms to weigh in and prevalidate
>> incoming address range before proceeding further with the memory hotplug.
>> This helps prevent potential platform errors for the given address range,
>> down the hotplug call chain, which inevitably fails the hotplug itself.
>>
>> This mechanism was suggested by David Hildenbrand during another discussion
>> with respect to a memory hotplug fix on arm64 platform.
>>
>> https://lore.kernel.org/linux-arm-kernel/1600332402-30123-1-git-send-email-anshuman.khandual@arm.com/
>>
>> This mechanism focuses on the addressibility aspect and not [sub] section
>> alignment aspect. Hence check_hotplug_memory_range() and check_pfn_span()
>> have been left unchanged. Wondering if all these can still be unified in
>> an expanded memhp_range_allowed() check, that can be called from multiple
>> memory hot add and remove paths.
>>
>> This series applies on v5.10-rc6 and has been slightly tested on arm64.
>> But looking for some early feedback here.
>>
>> Changes in RFC V2:
>>
>> Incorporated all review feedbacks from David.
>>
>> - Added additional range check in __segment_load() on s390 which was lost
>> - Changed is_private init in pagemap_range()
>> - Moved the framework into mm/memory_hotplug.c
>> - Made arch_get_addressable_range() a __weak function
>> - Renamed arch_get_addressable_range() as arch_get_mappable_range()
>> - Callback arch_get_mappable_range() only handles range requiring linear mapping
>> - Merged multiple memhp_range_allowed() checks in register_memory_resource()
>> - Replaced WARN() with pr_warn() in memhp_range_allowed()
>> - Replaced error return code ERANGE with E2BIG
>>
>> Changes in RFC V1:
>>
>> https://lore.kernel.org/linux-mm/1606098529-7907-1-git-send-email-anshuman.khandual@arm.com/
>>
>> Cc: Heiko Carstens <hca@...ux.ibm.com>
>> Cc: Vasily Gorbik <gor@...ux.ibm.com>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Ard Biesheuvel <ardb@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-s390@...r.kernel.org
>> Cc: linux-mm@...ck.org
>> Cc: linux-kernel@...r.kernel.org
> 
> Btw. please use git send-email's --cc-cover option to make sure that
> all patches of this series will be sent to all listed cc's.
> I really dislike to receive only the cover-letter and maybe on patch
> and then have to figure out where to find the rest.

Okay, will ensure that.

> 
> Thanks :)
>