Re: [Xen-devel] [PATCH RFC 27/55] x86_64/mm: drop lXe_to_lYe invocations from setup_m2p_table

["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 | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
> index 0b85961105..216f97c95f 100644
> --- a/xen/arch/x86/x86_64/mm.c
> +++ b/xen/arch/x86/x86_64/mm.c
> @@ -400,11 +400,13 @@ static int setup_m2p_table(struct
> mem_hotadd_info *info)
>      l2_pgentry_t *pl2e = NULL, *l2_ro_mpt = NULL;
>      l3_pgentry_t *l3_ro_mpt = NULL;
>      int ret = 0;
> -    mfn_t l2_ro_mpt_mfn;
> +    mfn_t l2_ro_mpt_mfn, l3_ro_mpt_mfn;
>  
>      ASSERT(l4e_get_flags(idle_pg_table[l4_table_offset(RO_MPT_VIRT_S
> TART)])
>              & _PAGE_PRESENT);
> -    l3_ro_mpt =
> l4e_to_l3e(idle_pg_table[l4_table_offset(RO_MPT_VIRT_START)]);
> +    l3_ro_mpt_mfn = l4e_get_mfn(idle_pg_table[l4_table_offset(
> +                                        RO_MPT_VIRT_START)]);
> +    l3_ro_mpt = map_xen_pagetable_new(l3_ro_mpt_mfn);
>  
>      smap = (info->spfn & (~((1UL << (L2_PAGETABLE_SHIFT - 3)) -1)));
>      emap = ((info->epfn + ((1UL << (L2_PAGETABLE_SHIFT - 3)) - 1 ))
> &
> @@ -459,8 +461,13 @@ static int setup_m2p_table(struct
> mem_hotadd_info *info)
>                    _PAGE_PSE));
>              if ( l3e_get_flags(l3_ro_mpt[l3_table_offset(va)]) &
>                _PAGE_PRESENT )
> -                pl2e = l3e_to_l2e(l3_ro_mpt[l3_table_offset(va)]) +
> -                  l2_table_offset(va);
> +            {
> +                UNMAP_XEN_PAGETABLE_NEW(l2_ro_mpt);
> +                l2_ro_mpt_mfn =
> l3e_get_mfn(l3_ro_mpt[l3_table_offset(va)]);
> +                l2_ro_mpt = map_xen_pagetable_new(l2_ro_mpt_mfn);
> +                ASSERT(l2_ro_mpt);

Do we need this assert here? What are the possibilities to recover from
that situation? I think this should be BUG_ON or it should at least
return through the error path.

- Stefan

> +                pl2e = l2_ro_mpt + l2_table_offset(va);
> +            }
>              else
>              {
>                  UNMAP_XEN_PAGETABLE_NEW(l2_ro_mpt);
> @@ -492,6 +499,7 @@ static int setup_m2p_table(struct mem_hotadd_info
> *info)
>      ret = setup_compat_m2p_table(info);
>  error:
>      UNMAP_XEN_PAGETABLE_NEW(l2_ro_mpt);
> +    UNMAP_XEN_PAGETABLE_NEW(l3_ro_mpt);
>      return ret;
>  }
>  



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