Re: [Xen-devel] [PATCH v2 12/18] mini-os: don't allocate new pages for level 1 p2m tree

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Juergen Gross, on Fri 05 Aug 2016 19:35:56 +0200, wrote:
> When constructing the 3 level p2m tree there is no need to allocate
> new pages for the level 1 containing the p2m info for all pages. The
> pages from the linear p2m list constructed by the hypervisor can be
> used for that purpose.
> 
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

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

> ---
>  arch/x86/mm.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/mm.c b/arch/x86/mm.c
> index 12f7fe4..e10c2c5 100644
> --- a/arch/x86/mm.c
> +++ b/arch/x86/mm.c
> @@ -625,11 +625,11 @@ void arch_init_p2m(unsigned long max_pfn)
>  #define L2_P2M_MASK     (L2_P2M_ENTRIES - 1)    
>  #define L3_P2M_MASK     (L3_P2M_ENTRIES - 1)    
>      
> -    unsigned long *l1_list = NULL, *l2_list = NULL, *l3_list;
> +    unsigned long *l2_list = NULL, *l3_list;
>      unsigned long pfn;
>      
>      l3_list = (unsigned long *)alloc_page(); 
> -    for ( pfn=0; pfn<max_pfn; pfn++ )
> +    for ( pfn = 0; pfn < max_pfn; pfn += L1_P2M_ENTRIES )
>      {
>          if ( !(pfn % (L1_P2M_ENTRIES * L2_P2M_ENTRIES)) )
>          {
> @@ -641,14 +641,8 @@ void arch_init_p2m(unsigned long max_pfn)
>              }
>              l3_list[(pfn >> L2_P2M_SHIFT)] = virt_to_mfn(l2_list);  
>          }
> -        if ( !(pfn % (L1_P2M_ENTRIES)) )
> -        {
> -            l1_list = (unsigned long*)alloc_page();
> -            l2_list[(pfn >> L1_P2M_SHIFT) & L2_P2M_MASK] = 
> -                virt_to_mfn(l1_list); 
> -        }
> -
> -        l1_list[pfn & L1_P2M_MASK] = pfn_to_mfn(pfn); 
> +        l2_list[(pfn >> L1_P2M_SHIFT) & L2_P2M_MASK] =
> +            virt_to_mfn(phys_to_machine_mapping + pfn);
>      }
>      HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = 
>          virt_to_mfn(l3_list);
> -- 
> 2.6.6
> 

-- 
Samuel
>Ever heard of .cshrc?
That's a city in Bosnia.  Right?
(Discussion in comp.os.linux.misc on the intuitiveness of commands.)

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