Re: [RFC XEN PATCH 02/16] x86_64/mm: explicitly specify the location to place the M2P table

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Mon, Oct 10, 2016 at 08:32:21AM +0800, Haozhong Zhang wrote:
> A reserved area on each pmem region is used to place the M2P table.
> However, it's not at the beginning of the pmem region, so we need to
> specify the location explicitly when creating the M2P table.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> ---
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
>  xen/arch/x86/x86_64/mm.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
> index 33f226a..5c0f527 100644
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -317,7 +317,8 @@ void destroy_m2p_mapping(struct mem_hotadd_info *info)
>   * spfn/epfn: the pfn ranges to be setup
>   * free_s/free_e: the pfn ranges that is free still
>   */
> -static int setup_compat_m2p_table(struct mem_hotadd_info *info)
> +static int setup_compat_m2p_table(struct mem_hotadd_info *info,
> +                                  struct mem_hotadd_info *alloc_info)
>  {
>      unsigned long i, va, smap, emap, rwva, epfn = info->epfn, mfn;
>      unsigned int n;
> @@ -371,7 +372,7 @@ static int setup_compat_m2p_table(struct mem_hotadd_info *info)
>          if ( n == CNT )
>              continue;
>  
> -        mfn = alloc_hotadd_mfn(info);
> +        mfn = alloc_hotadd_mfn(alloc_info);
>          err = map_pages_to_xen(rwva, mfn, 1UL << PAGETABLE_ORDER,
>                                 PAGE_HYPERVISOR);
>          if ( err )
> @@ -391,7 +392,8 @@ static int setup_compat_m2p_table(struct mem_hotadd_info *info)
>   * Allocate and map the machine-to-phys table.
>   * The L3 for RO/RWRW MPT and the L2 for compatible MPT should be setup already
>   */
> -static int setup_m2p_table(struct mem_hotadd_info *info)
> +static int setup_m2p_table(struct mem_hotadd_info *info,
> +                           struct mem_hotadd_info *alloc_info)
>  {
>      unsigned long i, va, smap, emap;
>      unsigned int n;
> @@ -440,7 +442,7 @@ static int setup_m2p_table(struct mem_hotadd_info *info)
>                  break;
>          if ( n < CNT )
>          {
> -            unsigned long mfn = alloc_hotadd_mfn(info);
> +            unsigned long mfn = alloc_hotadd_mfn(alloc_info);
>  
>              ret = map_pages_to_xen(
>                          RDWR_MPT_VIRT_START + i * sizeof(unsigned long),
> @@ -485,7 +487,7 @@ static int setup_m2p_table(struct mem_hotadd_info *info)
>  #undef CNT
>  #undef MFN
>  
> -    ret = setup_compat_m2p_table(info);
> +    ret = setup_compat_m2p_table(info, alloc_info);
>  error:
>      return ret;
>  }
> @@ -1427,7 +1429,7 @@ int memory_add(unsigned long spfn, unsigned long epfn, unsigned int pxm)
>      total_pages += epfn - spfn;
>  
>      set_pdx_range(spfn, epfn);
> -    ret = setup_m2p_table(&info);
> +    ret = setup_m2p_table(&info, &info);

I am not sure I follow this logic. You are passing the same contents, it
is just that 'alloc_info' and 'info' are aliased together?


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