linux-kernel - Re: [PATCH V3 0/3] mm/memory_hotplug: Pre-validate the address range with platform

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Date:   Tue, 19 Jan 2021 14:33:03 +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:     Oscar Salvador <osalvador@...e.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 0/3] mm/memory_hotplug: Pre-validate the address range
 with platform

On 18.01.21 14:12, 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 v5.11-rc4 and has been tested on arm64. But only
> build tested on s390.
> 
> Changes in V3
> 
> - Updated the commit message in [PATCH 1/3]
> - Replaced 1 with 'true' and 0 with 'false' in memhp_range_allowed()
> - Updated memhp_range.end as VMEM_MAX_PHYS - 1 and updated vmem_add_mapping() on s390
> - Changed memhp_range_allowed() behaviour in __add_pages()
> - Updated __add_pages() to return E2BIG when memhp_range_allowed() fails for non-linear mapping based requests

Minor thing, we should make up our mind if we want to call stuff
internally "memhp_" or "mhp". I prefer the latter, because it is shorter.


-- 
Thanks,

David / dhildenb