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Subject: Re: [PATCH v7] RISC-V: enable XIP
To:     Mike Rapoport <rppt@linux.ibm.com>, Alex Ghiti <alex@ghiti.fr>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-mm@kvack.org,
        Vitaly Wool <vitaly.wool@konsulko.com>
References: <20210409065115.11054-1-alex@ghiti.fr>
 <3500f3cb-b660-5bbc-ae8d-0c9770e4a573@ghiti.fr>
 <be575094-badf-bac7-1629-36808ca530cc@redhat.com>
 <c4e78916-7e4c-76db-47f6-4dda3f09c871@ghiti.fr>
 <YHBEsDuEvPAnL8Vb@linux.ibm.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <e7e87306-bb04-2d4f-7e7f-aabd40dccb3b@redhat.com>
Date:   Fri, 9 Apr 2021 14:46:17 +0200
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>>> 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