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Re: [Xen-devel] [PATCH v4 16/19] mini-os: map page allocator's bitmap to virtual kernel area for ballooning



Juergen Gross, on Thu 11 Aug 2016 13:06:36 +0200, wrote:
> In case of CONFIG_BALLOON the page allocator's bitmap needs some space
> to be able to grow. Remap it to kernel virtual area if the preallocated
> area isn't large enough.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

> ---
> V4: - mm_bitmap* -> mm_alloc_bitmap* as requested by Samuel Thibault
> 
> V3: - add assertion as requested by Samuel Thibault
>     - rename functions to have mm_ prefix as requested by Samuel Thibault
> ---
>  balloon.c         | 18 ++++++++++++++++++
>  include/balloon.h |  2 ++
>  include/mm.h      |  6 ++++++
>  mm.c              | 44 +++++++++++++++++++++++---------------------
>  4 files changed, 49 insertions(+), 21 deletions(-)
> 
> diff --git a/balloon.c b/balloon.c
> index 1ec113d..0a3342c 100644
> --- a/balloon.c
> +++ b/balloon.c
> @@ -44,3 +44,21 @@ void get_max_pages(void)
>      nr_max_pages = ret;
>      printk("Maximum memory size: %ld pages\n", nr_max_pages);
>  }
> +
> +void mm_alloc_bitmap_remap(void)
> +{
> +    unsigned long i;
> +
> +    if ( mm_alloc_bitmap_size >= ((nr_max_pages + 1) >> (PAGE_SHIFT + 3)) )
> +        return;
> +
> +    for ( i = 0; i < mm_alloc_bitmap_size; i += PAGE_SIZE )
> +    {
> +        map_frame_rw(virt_kernel_area_end + i,
> +                     virt_to_mfn((unsigned long)(mm_alloc_bitmap) + i));
> +    }
> +
> +    mm_alloc_bitmap = (unsigned long *)virt_kernel_area_end;
> +    virt_kernel_area_end += round_pgup((nr_max_pages + 1) >> (PAGE_SHIFT + 
> 3));
> +    ASSERT(virt_kernel_area_end <= VIRT_DEMAND_AREA);
> +}
> diff --git a/include/balloon.h b/include/balloon.h
> index b0d0ebf..9154f44 100644
> --- a/include/balloon.h
> +++ b/include/balloon.h
> @@ -31,11 +31,13 @@ extern unsigned long virt_kernel_area_end;
>  
>  void get_max_pages(void);
>  void arch_remap_p2m(unsigned long max_pfn);
> +void mm_alloc_bitmap_remap(void);
>  
>  #else /* CONFIG_BALLOON */
>  
>  static inline void get_max_pages(void) { }
>  static inline void arch_remap_p2m(unsigned long max_pfn) { }
> +static inline void mm_alloc_bitmap_remap(void) { }
>  
>  #endif /* CONFIG_BALLOON */
>  #endif /* _BALLOON_H_ */
> diff --git a/include/mm.h b/include/mm.h
> index 6add683..fc3128b 100644
> --- a/include/mm.h
> +++ b/include/mm.h
> @@ -42,8 +42,14 @@
>  #define STACK_SIZE_PAGE_ORDER __STACK_SIZE_PAGE_ORDER
>  #define STACK_SIZE __STACK_SIZE
>  
> +#define round_pgdown(_p)  ((_p) & PAGE_MASK)
> +#define round_pgup(_p)    (((_p) + (PAGE_SIZE - 1)) & PAGE_MASK)
> +
>  extern unsigned long nr_free_pages;
>  
> +extern unsigned long *mm_alloc_bitmap;
> +extern unsigned long mm_alloc_bitmap_size;
> +
>  void init_mm(void);
>  unsigned long alloc_pages(int order);
>  #define alloc_page()    alloc_pages(0)
> diff --git a/mm.c b/mm.c
> index 707a3e0..9e3a479 100644
> --- a/mm.c
> +++ b/mm.c
> @@ -48,11 +48,14 @@
>   *  One bit per page of memory. Bit set => page is allocated.
>   */
>  
> -static unsigned long *alloc_bitmap;
> +unsigned long *mm_alloc_bitmap;
> +unsigned long mm_alloc_bitmap_size;
> +
>  #define PAGES_PER_MAPWORD (sizeof(unsigned long) * 8)
>  
>  #define allocated_in_map(_pn) \
> -(alloc_bitmap[(_pn)/PAGES_PER_MAPWORD] & 
> (1UL<<((_pn)&(PAGES_PER_MAPWORD-1))))
> +    (mm_alloc_bitmap[(_pn) / PAGES_PER_MAPWORD] & \
> +     (1UL << ((_pn) & (PAGES_PER_MAPWORD - 1))))
>  
>  unsigned long nr_free_pages;
>  
> @@ -61,8 +64,8 @@ unsigned long nr_free_pages;
>   *  -(1<<n)  sets all bits >= n. 
>   *  (1<<n)-1 sets all bits <  n.
>   * Variable names in map_{alloc,free}:
> - *  *_idx == Index into `alloc_bitmap' array.
> - *  *_off == Bit offset within an element of the `alloc_bitmap' array.
> + *  *_idx == Index into `mm_alloc_bitmap' array.
> + *  *_off == Bit offset within an element of the `mm_alloc_bitmap' array.
>   */
>  
>  static void map_alloc(unsigned long first_page, unsigned long nr_pages)
> @@ -76,13 +79,13 @@ static void map_alloc(unsigned long first_page, unsigned 
> long nr_pages)
>  
>      if ( curr_idx == end_idx )
>      {
> -        alloc_bitmap[curr_idx] |= ((1UL<<end_off)-1) & -(1UL<<start_off);
> +        mm_alloc_bitmap[curr_idx] |= ((1UL<<end_off)-1) & -(1UL<<start_off);
>      }
>      else 
>      {
> -        alloc_bitmap[curr_idx] |= -(1UL<<start_off);
> -        while ( ++curr_idx < end_idx ) alloc_bitmap[curr_idx] = ~0UL;
> -        alloc_bitmap[curr_idx] |= (1UL<<end_off)-1;
> +        mm_alloc_bitmap[curr_idx] |= -(1UL<<start_off);
> +        while ( ++curr_idx < end_idx ) mm_alloc_bitmap[curr_idx] = ~0UL;
> +        mm_alloc_bitmap[curr_idx] |= (1UL<<end_off)-1;
>      }
>  
>      nr_free_pages -= nr_pages;
> @@ -102,13 +105,13 @@ static void map_free(unsigned long first_page, unsigned 
> long nr_pages)
>  
>      if ( curr_idx == end_idx )
>      {
> -        alloc_bitmap[curr_idx] &= -(1UL<<end_off) | ((1UL<<start_off)-1);
> +        mm_alloc_bitmap[curr_idx] &= -(1UL<<end_off) | ((1UL<<start_off)-1);
>      }
>      else 
>      {
> -        alloc_bitmap[curr_idx] &= (1UL<<start_off)-1;
> -        while ( ++curr_idx != end_idx ) alloc_bitmap[curr_idx] = 0;
> -        alloc_bitmap[curr_idx] &= -(1UL<<end_off);
> +        mm_alloc_bitmap[curr_idx] &= (1UL<<start_off)-1;
> +        while ( ++curr_idx != end_idx ) mm_alloc_bitmap[curr_idx] = 0;
> +        mm_alloc_bitmap[curr_idx] &= -(1UL<<end_off);
>      }
>  }
>  
> @@ -137,9 +140,6 @@ static chunk_head_t *free_head[FREELIST_SIZE];
>  static chunk_head_t  free_tail[FREELIST_SIZE];
>  #define FREELIST_EMPTY(_l) ((_l)->next == NULL)
>  
> -#define round_pgdown(_p)  ((_p)&PAGE_MASK)
> -#define round_pgup(_p)    (((_p)+(PAGE_SIZE-1))&PAGE_MASK)
> -
>  /*
>   * Initialise allocator, placing addresses [@min,@max] in free pool.
>   * @min and @max are PHYSICAL addresses.
> @@ -147,7 +147,7 @@ static chunk_head_t  free_tail[FREELIST_SIZE];
>  static void init_page_allocator(unsigned long min, unsigned long max)
>  {
>      int i;
> -    unsigned long range, bitmap_size;
> +    unsigned long range;
>      chunk_head_t *ch;
>      chunk_tail_t *ct;
>      for ( i = 0; i < FREELIST_SIZE; i++ )
> @@ -161,14 +161,14 @@ static void init_page_allocator(unsigned long min, 
> unsigned long max)
>      max = round_pgdown(max);
>  
>      /* Allocate space for the allocation bitmap. */
> -    bitmap_size  = (max+1) >> (PAGE_SHIFT+3);
> -    bitmap_size  = round_pgup(bitmap_size);
> -    alloc_bitmap = (unsigned long *)to_virt(min);
> -    min         += bitmap_size;
> +    mm_alloc_bitmap_size  = (max + 1) >> (PAGE_SHIFT + 3);
> +    mm_alloc_bitmap_size  = round_pgup(mm_alloc_bitmap_size);
> +    mm_alloc_bitmap = (unsigned long *)to_virt(min);
> +    min         += mm_alloc_bitmap_size;
>      range        = max - min;
>  
>      /* All allocated by default. */
> -    memset(alloc_bitmap, ~0, bitmap_size);
> +    memset(mm_alloc_bitmap, ~0, mm_alloc_bitmap_size);
>      /* Free up the memory we've been given to play with. */
>      map_free(PHYS_PFN(min), range>>PAGE_SHIFT);
>  
> @@ -198,6 +198,8 @@ static void init_page_allocator(unsigned long min, 
> unsigned long max)
>          free_head[i]    = ch;
>          ct->level       = i;
>      }
> +
> +    mm_alloc_bitmap_remap();
>  }
>  
>  
> -- 
> 2.6.6
> 

-- 
Samuel
"...Deep Hack Mode--that mysterious and frightening state of
consciousness where Mortal Users fear to tread."
(By Matt Welsh)

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