linux-kernel - Re: [RFC PATCH 2/4] x86/setup: parse acpi to get hotplug info before init_mem

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Date:   Mon, 7 Jan 2019 09:11:39 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Pingfan Liu <kernelfans@...il.com>, x86@...nel.org,
        linux-acpi@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/4] x86/setup: parse acpi to get hotplug info before
 init_mem_mapping()


On 1/7/19 12:24 AM, Pingfan Liu wrote:
> At present, memblock bottom-up allocation can help us against stamping over
> movable node in very high probability.

Is this what you are fixing?  Making a "high probability", a certainty?
 Is this the problem?

> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index acbcd62..df4132c 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -805,6 +805,20 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p)
>  	return 0;
>  }
>  
> +/* only need the effect of acpi_numa_memory_affinity_init()
> + * ->memblock_mark_hotplug()
> + */

CodingStyle, please.

> +static int early_detect_acpi_memhotplug(void)
> +{
> +#ifdef CONFIG_ACPI_NUMA
> +	acpi_table_upgrade(__va(get_ramdisk_image()), get_ramdisk_size());

This adds a new, early, call to acpi_table_upgrade(), and presumably all
the following functions.  However, it does not remove any of the later
calls.  How do they interact with each other now that they are
presumably called twice?

> +	acpi_table_init();
> +	acpi_numa_init();
> +	acpi_tb_terminate();
> +#endif
> +	return 0;
> +}

Why does this return an 'int' that is unconsumed by its lone caller?

There seems to be a lack of comments on this newly-added code.

>  /*
>   * Determine if we were loaded by an EFI loader.  If so, then we have also been
>   * passed the efi memmap, systab, etc., so we should use these data structures
> @@ -1131,6 +1145,7 @@ void __init setup_arch(char **cmdline_p)
>  	trim_platform_memory_ranges();
>  	trim_low_memory_range();
>  
> +	early_detect_acpi_memhotplug();

Comments, please.  Why is this call here, specifically?  What is it doing?