linux-kernel - Re: [RFC] depopulate_range_driver_managed() for removing page-table mappings for hot-added memory blocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <f1ff619d-5190-1181-6514-41f0c69ffe54@redhat.com>
Date:   Tue, 17 Nov 2020 15:58:49 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Sudarshan Rajagopalan <sudaraja@...eaurora.org>
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Mark Rutland <mark.rutland@....com>,
        Steven Price <steven.price@....com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Suren Baghdasaryan <surenb@...gle.com>,
        Pratik Patel <pratikp@...eaurora.org>
Subject: Re: [RFC] depopulate_range_driver_managed() for removing page-table
 mappings for hot-added memory blocks

On 14.11.20 11:28, Christoph Hellwig wrote:
> On Fri, Nov 13, 2020 at 06:41:22PM -0800, Sudarshan Rajagopalan wrote:
>>
>> Hello,
>>
>> When memory blocks are removed, along with removing the memmap entries,
>> memory resource and memory block devices, the arch specific
>> arch_remove_memory() is called which takes care of tearing down the
>> page-tables.
>>
>> Suppose there???s a usecase where the removed memory blocks will be added
>> back into the system at later point,
> 
> Stop this crap.  If you have a use case post the actual use here,
> including code and specs.  If you don't have that don't waste peoples
> time on your pipe dream.
> 

Adding to that, we (upstream people) are not interested in introducing 
and maintaining kernel interfaces/infrastructure only relevant to 
out-of-tree / proprietary drivers. If you're planning on upstreaming, 
then please share the actual problem you are trying to solve and the 
issues you see with the current interfaces/infrastructure, best along 
with an RFC that shows the bigger picture.

Having that said, what you describe sounds more like a special kind of 
allocation, whereby the linear mapping is removed, similar to [1].

[1] https://lkml.kernel.org/r/20201111145322.15793-1-david@redhat.com


-- 
Thanks,

David / dhildenb