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

[John Dorminy]

On Thu, Dec 9, 2021 at 10:19 AM Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> + Hugh and Patrick.
>
> On Thu, Dec 09, 2021 at 09:38:10AM -0500, John Dorminy wrote:
> > 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.
>
> Yeah, people have been reporting boot failures with mem= on the cmdline.
>
> I think I see why, can you try this one:
>
> ---
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 6a190c7f4d71..6db971e61e4b 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -862,6 +862,8 @@ void __init setup_arch(char **cmdline_p)
>          */
>         x86_configure_nx();
>
> +       e820__memory_setup();
> +
>         /*
>          * This parses early params and it needs to run before
>          * early_reserve_memory() because latter relies on such settings
> @@ -884,7 +886,6 @@ void __init setup_arch(char **cmdline_p)
>         early_reserve_memory();
>
>         iomem_resource.end = (1ULL << boot_cpu_data.x86_phys_bits) - 1;
> -       e820__memory_setup();
>         parse_setup_data();
>
>         copy_edd();
> ---
>
Confirmed that that patch makes mem= work again:

[    0.000000] Command line:
BOOT_IMAGE=(hd0,msdos1)/boot/vmlinuz-5.16.0-rc4+ root=UUID=0e
750e61-b92e-4708-a974-c50a3fb7e969 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
...
[    0.025520] Memory: 1762976K/2061136K available (16394K kernel
code, 3568K rwdata, 10328K rodata, 2676K init, 4924K bss, 297900K
reserved, 0K cma-reserved)