linux-kernel - Re: [PATCH] x86/e820: make e820 type string uniform

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Date:   Fri, 21 Oct 2022 02:52:09 +0000
From:   "Yajun Deng" <yajun.deng@...ux.dev>
To:     "Dave Hansen" <dave.hansen@...el.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com
Cc:     noodles@...com, ross.philipson@...cle.com, daniel.kiper@...cle.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/e820: make e820 type string uniform

October 20, 2022 11:44 PM, "Dave Hansen" <dave.hansen@...el.com> wrote:

> On 10/20/22 04:56, Yajun Deng wrote:
> 
>> /proc/iomem:
>> ...
>> 00000000-00000fff : Reserved
>> 00001000-0005efff : System RAM
>> 0005f000-0005ffff : Reserved
>> 00060000-0009ffff : System RAM
>> 000a0000-000fffff : Reserved
>> 000a0000-000bffff : PCI Bus 0000:00
>> 000c0000-000cddff : Video ROM
>> 000f0000-000fffff : System ROM
>> 00100000-80ff3017 : System RAM
>> 80ff3018-81003e57 : System RAM (kernel)
>> 81003e58-81004017 : System RAM
>> 81004018-81023c57 : System RAM (kernel)
>> 81023c58-87672fff : System RAM
> 
> I guess this is a pretty minimal change. It definitely makes
> /proc/iomem more human-readable.
> 
> Did you consider if this change might break any users of this file?

Yes, it may be.
I don't know how many users use this file, but I think the impact of this change is limited.

1st: This is not the first time this file has been changed. In commit 
     ad5fb870c486("e820, efi: add ACPI 6.0 persistent memory types"), the E820_PRAM changed 
     from "Persistent RAM" to "Persistent Memory (legacy)".

2nd: only super users can access the full information from /proc/iomem, which means the users
     of this file are limited.
     In commit 51d7b120418e("/proc/iomem: only expose physical resource addresses to privileged users")

3rd: The E820_TYPE_RESERVED_KERN changed from "System RAM" to "System RAM (kernel)" is a minimal change,
     and it also contains the "System RAM" string.