Re: [PATCH] gnttab: cleanup of number-of-active-frames calculations

[Keir Fraser <keir@xen.org>]

On 11/09/2012 12:58, "Jan Beulich" <JBeulich@suse.com> wrote:

> max_nr_active_grant_frames() is merly is special case of
> num_act_frames_from_sha_frames(), so there's no need to have a special
> case implementation for it.
> 
> Further, some of the related definitions (including the "struct
> active_grant_entry" definition itself) can (and hence should) really be
> private to grant_table.c.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Keir Fraser <keir@xen.org>

> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -127,10 +127,45 @@ shared_entry_header(struct grant_table *
>      else
>          return &shared_entry_v2(t, ref).hdr;
>  }
> +
> +/* Active grant entry - used for shadowing GTF_permit_access grants. */
> +struct active_grant_entry {
> +    u32           pin;    /* Reference count information.             */
> +    domid_t       domid;  /* Domain being granted access.             */
> +    struct domain *trans_domain;
> +    uint32_t      trans_gref;
> +    unsigned long frame;  /* Frame being granted.                     */
> +    unsigned long gfn;    /* Guest's idea of the frame being granted. */
> +    unsigned      is_sub_page:1; /* True if this is a sub-page grant. */
> +    unsigned      start:15; /* For sub-page grants, the start offset
> +                               in the page.                           */
> +    unsigned      length:16; /* For sub-page grants, the length of the
> +                                grant.                                */
> +};
> +
>  #define ACGNT_PER_PAGE (PAGE_SIZE / sizeof(struct active_grant_entry))
>  #define active_entry(t, e) \
>      ((t)->active[(e)/ACGNT_PER_PAGE][(e)%ACGNT_PER_PAGE])
>  
> +static inline unsigned int
> +num_act_frames_from_sha_frames(const unsigned int num)
> +{
> +    /* How many frames are needed for the active grant table,
> +     * given the size of the shared grant table? */
> +    unsigned int sha_per_page = PAGE_SIZE / sizeof(grant_entry_v1_t);
> +    unsigned int num_sha_entries = num * sha_per_page;
> +    return (num_sha_entries + (ACGNT_PER_PAGE - 1)) / ACGNT_PER_PAGE;
> +}
> +
> +#define max_nr_active_grant_frames \
> +    num_act_frames_from_sha_frames(max_nr_grant_frames)
> +
> +static inline unsigned int
> +nr_active_grant_frames(struct grant_table *gt)
> +{
> +    return num_act_frames_from_sha_frames(nr_grant_frames(gt));
> +}
> +
>  /* Check if the page has been paged out, or needs unsharing.
>     If rc == GNTST_okay, *page contains the page struct with a ref taken.
>     Caller must do put_page(*page).
> @@ -2542,13 +2577,6 @@ do_grant_table_op(
>  #include "compat/grant_table.c"
>  #endif
>  
> -static unsigned int max_nr_active_grant_frames(void)
> -{
> -    return (((max_nr_grant_frames * (PAGE_SIZE / sizeof(grant_entry_v1_t))) +
> -                    ((PAGE_SIZE / sizeof(struct active_grant_entry))-1))
> -                   / (PAGE_SIZE / sizeof(struct active_grant_entry)));
> -}
> -
>  int 
>  grant_table_create(
>      struct domain *d)
> @@ -2565,7 +2593,7 @@ grant_table_create(
>  
>      /* Active grant table. */
>      if ( (t->active = xzalloc_array(struct active_grant_entry *,
> -                                    max_nr_active_grant_frames())) == NULL )
> +                                    max_nr_active_grant_frames)) == NULL )
>          goto no_mem_1;
>      for ( i = 0;
>            i < num_act_frames_from_sha_frames(INITIAL_NR_GRANT_FRAMES); i++ )
> --- a/xen/include/xen/grant_table.h
> +++ b/xen/include/xen/grant_table.h
> @@ -28,21 +28,6 @@
>  #include <asm/page.h>
>  #include <asm/grant_table.h>
>  
> -/* Active grant entry - used for shadowing GTF_permit_access grants. */
> -struct active_grant_entry {
> -    u32           pin;    /* Reference count information.             */
> -    domid_t       domid;  /* Domain being granted access.             */
> -    struct domain *trans_domain;
> -    uint32_t      trans_gref;
> -    unsigned long frame;  /* Frame being granted.                     */
> -    unsigned long gfn;    /* Guest's idea of the frame being granted. */
> -    unsigned      is_sub_page:1; /* True if this is a sub-page grant. */
> -    unsigned      start:15; /* For sub-page grants, the start offset
> -                               in the page.                           */
> -    unsigned      length:16; /* For sub-page grants, the length of the
> -                                grant.                                */
> -};
> -
>   /* Count of writable host-CPU mappings. */
>  #define GNTPIN_hstw_shift    (0)
>  #define GNTPIN_hstw_inc      (1 << GNTPIN_hstw_shift)
> @@ -147,23 +132,4 @@ static inline unsigned int grant_to_stat
>          GRANT_STATUS_PER_PAGE;
>  }
>  
> -static inline unsigned int
> -num_act_frames_from_sha_frames(const unsigned int num)
> -{
> -    /* How many frames are needed for the active grant table,
> -     * given the size of the shared grant table? */
> -    unsigned act_per_page = PAGE_SIZE / sizeof(struct active_grant_entry);
> -    unsigned sha_per_page = PAGE_SIZE / sizeof(grant_entry_v1_t);
> -    unsigned num_sha_entries = num * sha_per_page;
> -    unsigned num_act_frames =
> -        (num_sha_entries + (act_per_page-1)) / act_per_page;
> -    return num_act_frames;
> -}
> -
> -static inline unsigned int
> -nr_active_grant_frames(struct grant_table *gt)
> -{
> -    return num_act_frames_from_sha_frames(nr_grant_frames(gt));
> -}
> -
>  #endif /* __XEN_GRANT_TABLE_H__ */
> 
> 
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