linux-kernel - Re: [tip: x86/urgent] x86/boot: Pull up cmdline preparation and early param parsing

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Date:   Thu,  9 Dec 2021 09:38:10 -0500
From:   John Dorminy <jdorminy@...hat.com>
To:     tip-bot2@...utronix.de
Cc:     anjaneya.chagam@...el.com, bp@...e.de, dan.j.williams@...el.com,
        linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        stable@...r.kernel.org, x86@...nel.org
Subject: Re: [tip: x86/urgent] x86/boot: Pull up cmdline preparation and early param parsing

Greetings;

It seems that this patch causes a mem= parameter to the kernel to have no effect, unfortunately... 

As far as I understand, the x86 mem parameter handler parse_memopt() (called by parse_early_param()) relies on being called after e820__memory_setup(): it simply removes any memory above the specified limit at that moment, allowing memory to later be hotplugged without regard for the initial limit. However, the initial non-hotplugged memory must already have been set up, in e820__memory_setup(), so that it can be removed in parse_memopt(); if parse_early_param() is called before e820__memory_setup(), as this change does, the parameter ends up having no effect.

I apologize that I don't know how to fix this, but I'm happy to test patches.

Typical dmesg output showing the lack of effect, built from the prior change and this change:

With a git tree synced to 8d48bf8206f77aa8687f0e241e901e5197e52423^ (working):
[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/boot/vmlinuz-5.16.0-rc1 root=UUID=a4f7bd84-4f29-40bc-8c98-f4a72d0856c4 ro net.ifnames=0 crashkernel=128M mem=4G
...
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009abff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009ac00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007dd3afff] usable
[    0.000000] BIOS-e820: [mem 0x000000007dd3b000-0x000000007deeffff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007def0000-0x000000007e0d3fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007e0d4000-0x000000007f367fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007f368000-0x000000007f7fffff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x0000000080000000-0x000000008fffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed3ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000207fffffff] usable
[    0.000000] e820: remove [mem 0x100000000-0xfffffffffffffffe] usable
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] user-defined physical RAM map:
[    0.000000] user: [mem 0x0000000000000000-0x000000000009abff] usable
[    0.000000] user: [mem 0x000000000009ac00-0x000000000009ffff] reserved
[    0.000000] user: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] user: [mem 0x0000000000100000-0x000000007dd3afff] usable
[    0.000000] user: [mem 0x000000007dd3b000-0x000000007deeffff] reserved
[    0.000000] user: [mem 0x000000007def0000-0x000000007e0d3fff] ACPI NVS
[    0.000000] user: [mem 0x000000007e0d4000-0x000000007f367fff] reserved
[    0.000000] user: [mem 0x000000007f368000-0x000000007f7fffff] ACPI NVS
[    0.000000] user: [mem 0x0000000080000000-0x000000008fffffff] reserved
[    0.000000] user: [mem 0x00000000fed1c000-0x00000000fed3ffff] reserved
[    0.000000] user: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
...
[    0.025617] Memory: 1762876K/2061136K available (16394K kernel code, 3568K rwdata, 10324K rodata, 2676K init, 4924K bss, 298000K reserved, 0K cma-reserved)

Synced 8d48bf8206f77aa8687f0e241e901e5197e52423 (not working):

[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/boot/vmlinuz-5.16.0-rc4+ root=UUID=0e750e61-b92e-4708-a974-c50a3fb7e969 ro net.ifnames=0 crashkernel=128M mem=4G
[    0.000000] e820: remove [mem 0x100000000-0xfffffffffffffffe] usable
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009abff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009ac00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007dd3afff] usable
[    0.000000] BIOS-e820: [mem 0x000000007dd3b000-0x000000007deeffff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007def0000-0x000000007e0d3fff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007e0d4000-0x000000007f367fff] reserved
[    0.000000] BIOS-e820: [mem 0x000000007f368000-0x000000007f7fffff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x0000000080000000-0x000000008fffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed3ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000207fffffff] usable
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] user-defined physical RAM map:
[    0.000000] user: [mem 0x0000000000000000-0x000000000009abff] usable
[    0.000000] user: [mem 0x000000000009ac00-0x000000000009ffff] reserved
[    0.000000] user: [mem 0x00000000000e0000-0x00000000000fffff] reserved
[    0.000000] user: [mem 0x0000000000100000-0x000000007dd3afff] usable
[    0.000000] user: [mem 0x000000007dd3b000-0x000000007deeffff] reserved
[    0.000000] user: [mem 0x000000007def0000-0x000000007e0d3fff] ACPI NVS
[    0.000000] user: [mem 0x000000007e0d4000-0x000000007f367fff] reserved
[    0.000000] user: [mem 0x000000007f368000-0x000000007f7fffff] ACPI NVS
[    0.000000] user: [mem 0x0000000080000000-0x000000008fffffff] reserved
[    0.000000] user: [mem 0x00000000fed1c000-0x00000000fed3ffff] reserved
[    0.000000] user: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
[    0.000000] user: [mem 0x0000000100000000-0x000000207fffffff] usable
...
[    0.695267] Memory: 131657608K/134181712K available (16394K kernel code, 3568K rwdata, 10328K rodata, 2676K init, 4924K bss, 2523844K reserved, 0K cma-reserved)