linux-kernel - Re: [PATCH 3/7] RISC-V: Rework kernel's virtual address space mapping

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Date:   Thu, 28 Mar 2019 09:54:01 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Anup Patel <anup@...infault.org>,
        Palmer Dabbelt <palmer@...ive.com>
Cc:     sorear2@...il.com, Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup.patel@....com>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        sbates@...thlin.com, antonynpavlov@...il.com,
        linux-riscv@...ts.infradead.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH 3/7] RISC-V: Rework kernel's virtual address space mapping



On 2019-03-28 12:28 a.m., Anup Patel wrote:
>>> For the MAXPHYSMEM_2GB case, the physical memory must be in the highest
>>> 2GB of address space, so we cannot cover the any of the I/O regions
>>> that are higher than it but we do cover the lower I/O TileLink range.
>>
>> IIRC there was another patch floating around to fix an issue with overlapping
>> regions in the 32-bit port, did you also fix that issue?  It's somewhere in my
>> email queue...
> 
> That was a patch I submitted to fix overlapping FIXMAP and VMALLOC
> regions.
> 
> This patch does not consider FIXMAP region.

Correct.

> I suggest we introduce asm/memory.h where we have all critical defines
> related to virtual memory layout. Also, this header should have detailed
> comments about virtual memory layout.

Seems like a sensible cleanup. It did seem like the defines for this
stuff were all over the place. I'm not really clear on all the stuff
that would belong in asm/memory.h so I think I'll leave such a cleanup
to you.

The second patch in this series added documentation to describe the
virtual memory layout which matches how it was done in x86.

Logan