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

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Date:   Fri, 9 Apr 2021 16:16:50 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Alex Ghiti <alex@...ti.fr>,
        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

On 09.04.21 16:10, Mike Rapoport wrote:
> On Fri, Apr 09, 2021 at 02:07:24PM +0200, David Hildenbrand wrote:
>> On 09.04.21 13:39, Alex Ghiti wrote:
>>> Hi David,
>>
>> I assume you still somehow create the direct mapping for the kernel, right?
>> So it's really some memory region with a direct mapping but without a memmap
>> (and right now, without a resource), correct?
> 
> XIP kernel text is not a region in memory to begin with ;-)

I think that's the part that confused me. I thought it would be mapped 
somehow into physical address space and would be addressed like other 
memory -- just that reads would be rewired to go to flash.

> 
> It resides in a flash and it is executed directly from there without being
> relocated to RAM.
> 
> That's why it does not need neither direct mapping, nor struct pages.

Thanks for clarifying! :)

-- 
Thanks,

David / dhildenb