Re: [Xen-devel] [PATCH 7/8] x86/mm: handle foreign mappings in p2m_entry_modify

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.01.19 at 11:36, <roger.pau@xxxxxxxxxx> wrote:
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -933,9 +933,12 @@ struct hvm_ioreq_server *p2m_get_ioreq_server(struct 
> domain *d,
>                                                unsigned int *flags);
>  
>  static inline void p2m_entry_modify(struct p2m_domain *p2m, p2m_type_t nt,
> -                                    p2m_type_t ot, unsigned int level)
> +                                    p2m_type_t ot, mfn_t nfn, mfn_t ofn,
> +                                    unsigned int level)
>  {
> -    if ( level != 1 || nt == ot )
> +    struct page_info *pg;
> +
> +    if ( level != 1 || (nt == ot && mfn_eq(nfn, ofn)) )
>          return;
>  
>      switch ( nt )
> @@ -948,6 +951,17 @@ static inline void p2m_entry_modify(struct p2m_domain 
> *p2m, p2m_type_t nt,
>          p2m->ioreq.entry_count++;
>          break;
>  
> +    case p2m_map_foreign:
> +        pg = mfn_to_page(nfn);
> +
> +        if ( !pg || !page_get_owner_and_reference(pg) )

mfn_to_page() can't return NULL, can it? You may want to ASSERT()
beforehand that the MFN is not INVALID_MFN, though.

Jan



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