linux-kernel - Re: [PATCH v5 03/22] x86, ACPI, mm: Kill max_low_pfn

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Message-ID: <1371511164.27152.22.camel@misato.fc.hp.com>
Date:	Mon, 17 Jun 2013 17:19:24 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Thomas Renninger <trenn@...e.de>,
	Tang Chen <tangchen@...fujitsu.com>,
	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 v5 03/22] x86, ACPI, mm: Kill max_low_pfn_mapped

On Fri, 2013-06-14 at 17:56 -0700, Yinghai Lu wrote:
> Now we have arch_pfn_mapped array, and max_low_pfn_mapped should not
> be used anymore.

Can you describe why max_low_pfn_mapped should not be used?  Is this to
allow moving the code of acpi_initrd_override() up before
init_mem_mapping() in a succeeding patch, or is there also another
reason behind it?  Also, I think arch_pfn_mapped should be pfn_mapped[].

Thanks,
-Toshi


> 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>
> Reviewed-by: Tang Chen <tangchen@...fujitsu.com>
> Tested-by: Tang Chen <tangchen@...fujitsu.com>
> ---
>  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 66ab495..6ca5f2c 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -112,13 +112,11 @@
>  #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 eaac174..8554656 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 e721863..93e3194 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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