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

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Date:   Thu, 17 Dec 2020 18:31:24 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org, hca@...ux.ibm.com,
        catalin.marinas@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH V2 0/3] mm/hotplug: Pre-validate the address range with
 platform

On 17.12.20 16:28, 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 and has been tested on arm64. But only
> build tested on s390.
> 
> Changes in V2:
> 
> - Changed s390 version per Heiko and updated the commit message
> - Called memhp_range_allowed() only for arch_add_memory() in pagemap_range()
> - Exported the symbol memhp_get_pluggable_range() 
> 
> Changes in V1:
> 
> https://lore.kernel.org/linux-mm/1607400978-31595-1-git-send-email-anshuman.khandual@arm.com/
> 
> - Fixed build problems with (MEMORY_HOTPLUG & !MEMORY_HOTREMOVE)
> - Added missing prototype for arch_get_mappable_range()
> - Added VM_BUG_ON() check for memhp_range_allowed() in arch_add_memory() per David
> 
> Changes in RFC V2:
> 
> https://lore.kernel.org/linux-mm/1606706992-26656-1-git-send-email-anshuman.khandual@arm.com/
> 
> 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
> 
> Anshuman Khandual (3):
>   mm/hotplug: Prevalidate the address range being added with platform
>   arm64/mm: Define arch_get_mappable_range()
>   s390/mm: Define arch_get_mappable_range()

Thanks, I'm planning on reviewing + sending a virtio-mem patch to use
memhp_get_mappable_range() in the new year. I assume we also have
restrictions when it comes to x86-64, will have a look.


-- 
Thanks,

David / dhildenb