Re: [Xen-devel] [PATCH 6 of 9] x86/mm: New domctl: add a shared page to the physmap

["Jan Beulich" <JBeulich@xxxxxxxx>]

 >>> On 09.12.11 at 21:22, Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> wrote:
> This domctl is useful to, for example, populate parts of a domain's
> physmap with shared frames, directly.

As said before - there's no consumer of this new code within the series,
and hence you're asking to add dead code. That's no appropriate imo.

Jan

> Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
> 
> diff -r bfebf49b3eb6 -r bba44de8394a xen/arch/x86/mm/mem_sharing.c
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -851,6 +851,74 @@ err_out:
>      return ret;
>  }
>  
> +int mem_sharing_add_to_physmap(struct domain *sd, unsigned long sgfn, 
> shr_handle_t sh,
> +                            struct domain *cd, unsigned long cgfn) 
> +{
> +    struct page_info *spage;
> +    int ret = -EINVAL;
> +    mfn_t smfn, cmfn;
> +    p2m_type_t smfn_type, cmfn_type;
> +    struct gfn_info *gfn_info;
> +    struct p2m_domain *p2m = p2m_get_hostp2m(cd);
> +    p2m_access_t a;
> +    DECLARE_PG_LOCK_DATA(pld);
> +    
> +    /* XXX if sd == cd handle potential deadlock by ordering
> +     * the get_ and put_gfn's */
> +    smfn = get_gfn_query(sd, sgfn, &smfn_type);
> +    cmfn = get_gfn_type_access(p2m, cgfn, &cmfn_type, &a, p2m_query, NULL);
> +
> +    /* Get the source shared page, check and lock */
> +    ret = XEN_DOMCTL_MEM_SHARING_S_HANDLE_INVALID;
> +    spage = __grab_shared_page(smfn, &pld);
> +    if ( spage == NULL )
> +        goto err_out;
> +    ASSERT(smfn_type == p2m_ram_shared);
> +
> +    /* Check that the handles match */
> +    if ( spage->shared_info->handle != sh )
> +        goto err_unlock;
> +
> +    /* Make sure the target page is a hole in the physmap */
> +    if ( mfn_valid(cmfn) ||
> +         (!(p2m_is_ram(cmfn_type))) )
> +    {
> +        ret = XEN_DOMCTL_MEM_SHARING_C_HANDLE_INVALID;
> +        goto err_unlock;
> +    }
> +
> +    /* This is simpler than regular sharing */
> +    BUG_ON(!get_page_and_type(spage, dom_cow, PGT_shared_page));
> +    if ( (gfn_info = mem_sharing_gfn_alloc(spage, cd, cgfn)) == NULL )
> +    {
> +        put_page_and_type(spage);
> +        ret = -ENOMEM;
> +        goto err_unlock;
> +    }
> +
> +    p2m_lock(p2m);
> +    ret = set_p2m_entry(p2m, cgfn, smfn, PAGE_ORDER_4K, p2m_ram_shared, a);
> +    p2m_unlock(p2m);
> +
> +    /* Tempted to turn this into an assert */
> +    if ( !ret ) {
> +        ret = -ENOENT;
> +        mem_sharing_gfn_destroy(gfn_info, 0);
> +        put_page_and_type(spage);
> +    } else {
> +        atomic_inc(&cd->shr_pages);
> +        atomic_inc(&nr_shared_mfns);
> +        ret = 0;
> +    }
> +
> +err_unlock:
> +    mem_sharing_page_unlock(spage, &pld);
> +err_out:
> +    put_gfn(cd, cgfn);
> +    put_gfn(sd, sgfn);
> +    return ret;
> +}
> +
>  int mem_sharing_unshare_page(struct domain *d,
>                               unsigned long gfn, 
>                               uint16_t flags)
> @@ -1085,6 +1153,42 @@ int mem_sharing_domctl(struct domain *d,
>          }
>          break;
>  
> +        case XEN_DOMCTL_MEM_EVENT_OP_SHARING_ADD_PHYSMAP:
> +        {
> +            unsigned long sgfn, cgfn;
> +            struct domain *cd;
> +            shr_handle_t sh;
> +
> +            if ( !mem_sharing_enabled(d) )
> +                return -EINVAL;
> +
> +            cd = get_domain_by_id(mec->u.share.client_domain);
> +            if ( !cd )
> +                return -ESRCH;
> +
> +            if ( !mem_sharing_enabled(cd) )
> +            {
> +                put_domain(cd);
> +                return -EINVAL;
> +            }
> +
> +            if ( 
> XEN_DOMCTL_MEM_SHARING_FIELD_IS_GREF(mec->u.share.source_gfn) )
> +            {
> +                /* Cannot add a gref to the physmap */
> +                put_domain(cd);
> +                return -EINVAL;
> +            }
> +
> +            sgfn    = mec->u.share.source_gfn;
> +            sh      = mec->u.share.source_handle;
> +            cgfn    = mec->u.share.client_gfn;
> +
> +            rc = mem_sharing_add_to_physmap(d, sgfn, sh, cd, cgfn); 
> +
> +            put_domain(cd);
> +        }
> +        break;
> +
>          case XEN_DOMCTL_MEM_EVENT_OP_SHARING_RESUME:
>          {
>              if ( !mem_sharing_enabled(d) )
> diff -r bfebf49b3eb6 -r bba44de8394a xen/include/public/domctl.h
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -771,6 +771,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_domctl_mem_e
>  #define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_GFN      5
>  #define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_MFN      6
>  #define XEN_DOMCTL_MEM_EVENT_OP_SHARING_DEBUG_GREF     7
> +#define XEN_DOMCTL_MEM_EVENT_OP_SHARING_ADD_PHYSMAP    8
>  
>  #define XEN_DOMCTL_MEM_SHARING_S_HANDLE_INVALID  (-10)
>  #define XEN_DOMCTL_MEM_SHARING_C_HANDLE_INVALID  (-9)
> @@ -797,7 +798,7 @@ struct xen_domctl_mem_sharing_op {
>              } u;
>              uint64_aligned_t  handle;     /* OUT: the handle           */
>          } nominate;
> -        struct mem_sharing_op_share {     /* OP_SHARE */
> +        struct mem_sharing_op_share {     /* OP_SHARE/ADD_PHYSMAP */
>              uint64_aligned_t source_gfn;    /* IN: the gfn of the source 
> page */
>              uint64_aligned_t source_handle; /* IN: handle to the source 
> page */
>              uint64_aligned_t client_domain; /* IN: the client domain id */



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