linux-kernel - Re: [PATCH v4 03/22] x86, ACPI, mm: Kill max_low_pfn

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Date:	Wed, 05 Jun 2013 16:36:40 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Thomas Renninger <trenn@...e.de>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Jacob Shin <jacob.shin@....com>,
	Pekka Enberg <penberg@...nel.org>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v4 03/22] x86, ACPI, mm: Kill max_low_pfn_mapped

Hi yinghai, HPA,

On 04/12/2013 08:55 AM, Yinghai Lu wrote:
> Now we have arch_pfn_mapped array, and max_low_pfn_mapped should not
> be used anymore.

I'm rebasing this patch-set to the latest kernel, and improving the
comment. But I didn't find any "arch_pfn_mapped array" in the kernel.

Would you please tell me what "arch_pfn_mapped array" is ?

Is it the "struct range pfn_mapped[E820_X_MAX];" in arch/x86/mm/init.c ?

Thanks. :)

>
> User should use arch_pfn_mapped or just 1UL<<(32-PAGE_SHIFT) instead.
>
> Only user is ACPI_INITRD_TABLE_OVERRIDE, and it should not use that,
> as later accessing is using early_ioremap(). We could change to use
> 1U<<(32_PAGE_SHIFT) with it, aka under 4G.
>
> -v2: Leave alone max_low_pfn_mapped in i915 code according to tj.
>
> Suggested-by: H. Peter Anvin<hpa@...or.com>
> Signed-off-by: Yinghai Lu<yinghai@...nel.org>
> Cc: "Rafael J. Wysocki"<rjw@...k.pl>
> Cc: Jacob Shin<jacob.shin@....com>
> Cc: Pekka Enberg<penberg@...nel.org>
> Cc: linux-acpi@...r.kernel.org
> Tested-by: Thomas Renninger<trenn@...e.de>
> ---
>   arch/x86/include/asm/page_types.h | 1 -
>   arch/x86/kernel/setup.c           | 4 +---
>   arch/x86/mm/init.c                | 4 ----
>   drivers/acpi/osl.c                | 6 +++---
>   4 files changed, 4 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
> index 54c9787..b012b82 100644
> --- a/arch/x86/include/asm/page_types.h
> +++ b/arch/x86/include/asm/page_types.h
> @@ -43,7 +43,6 @@
>
>   extern int devmem_is_allowed(unsigned long pagenr);
>
> -extern unsigned long max_low_pfn_mapped;
>   extern unsigned long max_pfn_mapped;
>
>   static inline phys_addr_t get_max_mapped(void)
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 1629577..e75c6e6 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -113,13 +113,11 @@
>   #include<asm/prom.h>
>
>   /*
> - * max_low_pfn_mapped: highest direct mapped pfn under 4GB
> - * max_pfn_mapped:     highest direct mapped pfn over 4GB
> + * max_pfn_mapped:     highest direct mapped pfn
>    *
>    * The direct mapping only covers E820_RAM regions, so the ranges and gaps are
>    * represented by pfn_mapped
>    */
> -unsigned long max_low_pfn_mapped;
>   unsigned long max_pfn_mapped;
>
>   #ifdef CONFIG_DMI
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 59b7fc4..abcc241 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -313,10 +313,6 @@ static void add_pfn_range_mapped(unsigned long start_pfn, unsigned long end_pfn)
>   	nr_pfn_mapped = clean_sort_range(pfn_mapped, E820_X_MAX);
>
>   	max_pfn_mapped = max(max_pfn_mapped, end_pfn);
> -
> -	if (start_pfn<  (1UL<<(32-PAGE_SHIFT)))
> -		max_low_pfn_mapped = max(max_low_pfn_mapped,
> -					 min(end_pfn, 1UL<<(32-PAGE_SHIFT)));
>   }
>
>   bool pfn_range_is_mapped(unsigned long start_pfn, unsigned long end_pfn)
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 586e7e9..313d14d 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -624,9 +624,9 @@ void __init acpi_initrd_override(void *data, size_t size)
>   	if (table_nr == 0)
>   		return;
>
> -	acpi_tables_addr =
> -		memblock_find_in_range(0, max_low_pfn_mapped<<  PAGE_SHIFT,
> -				       all_tables_size, PAGE_SIZE);
> +	/* under 4G at first, then above 4G */
> +	acpi_tables_addr = memblock_find_in_range(0, (1ULL<<32) - 1,
> +					all_tables_size, PAGE_SIZE);
>   	if (!acpi_tables_addr) {
>   		WARN_ON(1);
>   		return;
--
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