Re: [Xen-devel] [PATCH RFC 41/55] x86_64/mm: map and unmap page tables in m2p_mapped

["Nuernberger, Stefan" <snu@xxxxxxxxx>]

On Thu, 2019-02-07 at 16:44 +0000, Wei Liu wrote:
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/arch/x86/x86_64/mm.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
> index 216f97c95f..2b88a1af37 100644
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -130,28 +130,36 @@ static int m2p_mapped(unsigned long spfn)
>  {
>      unsigned long va;
>      l3_pgentry_t *l3_ro_mpt;
> -    l2_pgentry_t *l2_ro_mpt;
> +    l2_pgentry_t *l2_ro_mpt = NULL;
> +    int rc = M2P_NO_MAPPED;
>  
>      va = RO_MPT_VIRT_START + spfn *
> sizeof(*machine_to_phys_mapping);
> -    l3_ro_mpt = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]);
> +    l3_ro_mpt = map_xen_pagetable_new(
> +        l4e_get_mfn(idle_pg_table[l4_table_offset(va)]));
>  
>      switch ( l3e_get_flags(l3_ro_mpt[l3_table_offset(va)]) &
>               (_PAGE_PRESENT |_PAGE_PSE))
>      {
>          case _PAGE_PSE|_PAGE_PRESENT:
> -            return M2P_1G_MAPPED;
> +            rc = M2P_1G_MAPPED;
> +            goto out;
>          /* Check for next level */
>          case _PAGE_PRESENT:
>              break;
>          default:
> -            return M2P_NO_MAPPED;
> +            rc = M2P_NO_MAPPED;

nit: This assignment is redundant now, but it might stay for clarity.

- Stefan

> +            goto out;
>      }
> -    l2_ro_mpt = l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]);
> +    l2_ro_mpt = map_xen_pagetable_new(
> +        l3e_get_mfn(l3_ro_mpt[l3_table_offset(va)]));
>  
>      if (l2e_get_flags(l2_ro_mpt[l2_table_offset(va)]) &
> _PAGE_PRESENT)
> -        return M2P_2M_MAPPED;
> +        rc = M2P_2M_MAPPED;
>  
> -    return M2P_NO_MAPPED;
> + out:
> +    UNMAP_XEN_PAGETABLE_NEW(l2_ro_mpt);
> +    UNMAP_XEN_PAGETABLE_NEW(l3_ro_mpt);
> +    return rc;
>  }
>  
>  static int share_hotadd_m2p_table(struct mem_hotadd_info *info)



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