Re: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32 CPUs

[Nicolas Pitre]

On Fri, 11 Apr 2014, Liu Hua wrote:

> In 32-bit ARM systems, the fixmap mapping region can support
> no more than 14 CPUs(total: 896k; one CPU: 64K). And we can
> configure NR_CPUS up to 32. So there is a mismatch.
> 
> This patch moves fixmapping region downwards to region
> 0xffc00000-0xffe00000 . Then the fixmap mapping region can
> support up to 32 CPUs.
> 
> Signed-off-by: Liu Hua <sdu.liu@xxxxxxxxxx>

Comments below.

> ---
>  Documentation/arm/memory.txt   |  2 +-
>  arch/arm/include/asm/fixmap.h  |  4 ++--
>  arch/arm/include/asm/highmem.h |  1 +
>  arch/arm/mm/highmem.c          | 10 +++++-----
>  arch/arm/mm/mm.h               |  7 +++++++
>  arch/arm/mm/mmu.c              |  4 ++++
>  mm/highmem.c                   |  1 +
>  7 files changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/arm/memory.txt b/Documentation/arm/memory.txt
> index 8a361c0..4bca737 100644
> --- a/Documentation/arm/memory.txt
> +++ b/Documentation/arm/memory.txt
> @@ -41,7 +41,7 @@ fffe8000	fffeffff	DTCM mapping area for platforms with
>  fffe0000	fffe7fff	ITCM mapping area for platforms with
>  				ITCM mounted inside the CPU.
>  
> -fff00000	fffdffff	Fixmap mapping region.  Addresses provided
> +ffc00000	ffdfffff	Fixmap mapping region.  Addresses provided
>  				by fix_to_virt() will be located here.
>  
>  ff000000	ffbfffff	Reserved for future expansion of DMA
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index bbae919..014a70d 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -13,8 +13,8 @@
>   * 0xfffe0000 and 0xfffeffff.
>   */
>  
> -#define FIXADDR_START		0xfff00000UL
> -#define FIXADDR_TOP		0xfffe0000UL
> +#define FIXADDR_START		0xffc00000UL
> +#define FIXADDR_TOP		0xffe00000UL
>  #define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)
>  
>  #define FIX_KMAP_BEGIN		0
> diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
> index 91b99ab..5355795 100644
> --- a/arch/arm/include/asm/highmem.h
> +++ b/arch/arm/include/asm/highmem.h
> @@ -18,6 +18,7 @@
>  	} while (0)
>  
>  extern pte_t *pkmap_page_table;
> +extern pte_t *fixmap_page_table;
>  
>  extern void *kmap_high(struct page *page);
>  extern void kunmap_high(struct page *page);
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index 21b9e1b..9bc8988 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -69,14 +69,14 @@ void *kmap_atomic(struct page *page)
>  	 * With debugging enabled, kunmap_atomic forces that entry to 0.
>  	 * Make sure it was indeed properly unmapped.
>  	 */
> -	BUG_ON(!pte_none(get_top_pte(vaddr)));
> +	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
>  #endif
>  	/*
>  	 * When debugging is off, kunmap_atomic leaves the previous mapping
>  	 * in place, so the contained TLB flush ensures the TLB is updated
>  	 * with the new mapping.
>  	 */
> -	set_top_pte(vaddr, mk_pte(page, kmap_prot));
> +	set_fixmap_pte(idx, mk_pte(page, kmap_prot));
>  
>  	return (void *)vaddr;
>  }
> @@ -95,7 +95,7 @@ void __kunmap_atomic(void *kvaddr)
>  			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
>  #ifdef CONFIG_DEBUG_HIGHMEM
>  		BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
> -		set_top_pte(vaddr, __pte(0));
> +		set_fixmap_pte(idx, __pte(0));
>  #else
>  		(void) idx;  /* to kill a warning */
>  #endif
> @@ -119,9 +119,9 @@ void *kmap_atomic_pfn(unsigned long pfn)
>  	idx = type + KM_TYPE_NR * smp_processor_id();
>  	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
>  #ifdef CONFIG_DEBUG_HIGHMEM
> -	BUG_ON(!pte_none(get_top_pte(vaddr)));
> +	BUG_ON(!pte_none(*(fixmap_page_table + idx)));
>  #endif
> -	set_top_pte(vaddr, pfn_pte(pfn, kmap_prot));
> +	set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));
>  
>  	return (void *)vaddr;
>  }
> diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
> index 7ea641b..3460d73 100644
> --- a/arch/arm/mm/mm.h
> +++ b/arch/arm/mm/mm.h
> @@ -1,6 +1,7 @@
>  #ifdef CONFIG_MMU
>  #include <linux/list.h>
>  #include <linux/vmalloc.h>
> +#include <asm/fixmap.h>
>  
>  /* the upper-most page table pointer */
>  extern pmd_t *top_pmd;
> @@ -25,6 +26,12 @@ static inline void set_top_pte(unsigned long va, pte_t pte)
>  	local_flush_tlb_kernel_page(va);
>  }
>  
> +static inline void set_fixmap_pte(int idx, pte_t pte)
> +{
> +	unsigned long vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
> +	set_pte_ext(fixmap_page_table + idx, pte, 0);
> +	local_flush_tlb_kernel_page(vaddr);
> +}

This has no other users than the code in highmem.c so it probably should 
live there.

Other than that...

Acked-by: Nicolas Pitre <nico@xxxxxxxxxx>

>  static inline pte_t get_top_pte(unsigned long va)
>  {
>  	pte_t *ptep = pte_offset_kernel(top_pmd, va);
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index b68c6b2..09c0a16 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -35,6 +35,7 @@
>  #include <asm/mach/arch.h>
>  #include <asm/mach/map.h>
>  #include <asm/mach/pci.h>
> +#include <asm/fixmap.h>
>  
>  #include "mm.h"
>  #include "tcm.h"
> @@ -1359,6 +1360,9 @@ static void __init kmap_init(void)
>  #ifdef CONFIG_HIGHMEM
>  	pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
>  		PKMAP_BASE, _PAGE_KERNEL_TABLE);
> +
> +	fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
> +		FIXADDR_START, _PAGE_KERNEL_TABLE);
>  #endif
>  }
>  
> diff --git a/mm/highmem.c b/mm/highmem.c
> index b32b70c..d0094ba 100644
> --- a/mm/highmem.c
> +++ b/mm/highmem.c
> @@ -72,6 +72,7 @@ static unsigned int last_pkmap_nr;
>  static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
>  
>  pte_t * pkmap_page_table;
> +pte_t *fixmap_page_table;
>  
>  static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
>  
> -- 
> 1.9.0
> 
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