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Date:   Sat, 23 Mar 2019 10:24:21 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Mike Rapoport <rppt@linux.ibm.com>
Cc:     Anup Patel <Anup.Patel@wdc.com>, Albert Ou <aou@eecs.berkeley.edu>,
        Palmer Dabbelt <palmer@sifive.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Atish Patra <Atish.Patra@wdc.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>
Subject: Re: [PATCH v2 3/5] RISC-V: Allow booting kernel from any 4KB aligned
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Message-ID: <20190323172421.GA14080@infradead.org>
References: <20190321094710.16552-1-anup.patel@wdc.com>
 <20190321094710.16552-4-anup.patel@wdc.com>
 <20190323154012.GA25149@rapoport-lnx>
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On Sat, Mar 23, 2019 at 05:40:12PM +0200, Mike Rapoport wrote:
> I have no general objection, but I presume the patch will be significantly
> simplified if the addition of 4K pages support will follow the removal of
> the trampoline_pd_dir. 
> 
> That said, I didn't look into the details, since they will change
> substantially, only some comments on the Kconfig part.
> 
> On the high level, have you considered using large pages in setup_vm() and
> the remapping everything with 4K pages in setup_vm_final()?  This might
> save you the whole ops-> churn.

That would be a great start.  That being said the current tiny memory
RISC-V devices don't even have a MMU, so the kernel pagetable mapping
isn't even relevant for them.  I'm just not sure adding more complexity
in the early boot path for a borderline case (MMU and tiny memory
with a tiny kernel image) is reall worth all the complexity.