linux-kernel - Re: [PATCH v7] RISC-V: enable XIP

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Date:   Fri, 9 Apr 2021 14:46:17 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>, Alex Ghiti <alex@...ti.fr>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        Vitaly Wool <vitaly.wool@...sulko.com>
Subject: Re: [PATCH v7] RISC-V: enable XIP

>>> Also, will that memory properly be exposed in the resource tree as
>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>>> won't work as expected - the kernel won't be included in a dump.
>   
> Do we really need a XIP kernel to included in kdump?
> And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)

See my other mail, maybe we actually want something different.

> 
>> I have just checked and it does not appear in /proc/iomem.
>>
>> Ok your conclusion would be to have struct page, I'm going to implement this
>> version then using memblock as you described.
> 
> I'm not sure this is required. With XIP kernel text never gets into RAM, so
> it does not seem to require struct page.
> 
> XIP by definition has some limitations relatively to "normal" operation,
> so lack of kdump could be one of them.

I agree.

> 
> I might be wrong, but IMHO, artificially creating a memory map for part of
> flash would cause more problems in the long run.

Can you elaborate?

> 
> BTW, how does XIP account the kernel text on other architectures that
> implement it?

Interesting point, I thought XIP would be something new on RISC-V (well, 
at least to me :) ). If that concept exists already, we better mimic 
what existing implementations do.

-- 
Thanks,

David / dhildenb