Re: [Xen-devel] [PATCH 2/3] Grant tables v2 implementation.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-11-09 at 08:15 +0000, annie.li@xxxxxxxxxx wrote:
> From: Annie Li <annie.li@xxxxxxxxxx>
> 
> Receiver-side copying of packets is based on this implementation, it gives
> better performance and better CPU accounting. It totally supports three types:
> full-page, sub-page and transitive grants.
> 
> However this patch does not cover sub-page and transitive grants, it mainly
> focus on Full-page part and implements grant table V2 interfaces corresponding
> to what already exists in grant table V1, such as: grant table V2
> initialization, mapping, releasing and exported interfaces.
> 
> Each guest can only supports one type of grant table type, every entry in 
> grant
> table should be the same version. It is necessary to set V1 or V2 version 
> before
> initializing the grant table.
> 
> Grant table exported interfaces of V2 are same with those of V1, Xen is
> responsible to judge what grant table version guests are using in every grant
> operation.
> 
> V2 fulfills the same role of V1, and it is totally backwards compitable with 
> V1.
> If dom0 support grant table V2, the guests runing on it can run with either V1
> or V2.
> 
> Signed-off-by: Annie Li <annie.li@xxxxxxxxxx>
> ---
>  arch/x86/xen/grant-table.c |   34 ++++++++-
>  drivers/xen/grant-table.c  |  194 
> +++++++++++++++++++++++++++++++++++++++++---
>  include/xen/grant_table.h  |    6 +-
>  3 files changed, 220 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 65ce508..3e9f936 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -54,6 +54,17 @@ static int map_pte_fn(pte_t *pte, struct page *pmd_page,
>         return 0;
>  }
> 
> +/*32bits is not enough since Xen supports sparse physical memory*/

What does this mean?

> +static int map_pte_fn_status(pte_t *pte, struct page *pmd_page,
> +                            unsigned long addr, void *data)
> +{
> +       uint64_t **frames = (uint64_t **)data;
> +
> +       set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
> +       (*frames)++;
> +       return 0;
> +}

Isn't this function identical to map_pte_fn?

> +
>  static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,
>                         unsigned long addr, void *data)
>  {

> @@ -630,6 +756,44 @@ static int gnttab_map_status_v1(unsigned int nr_gframes)
>         return 0;
>  }
> 
> +static int gnttab_map_status_v2(unsigned int nr_gframes)
> +{
> +       uint64_t *sframes;
> +       unsigned int nr_sframes;
> +       struct gnttab_get_status_frames getframes;
> +       int rc;
> +
> +       nr_sframes = nr_status_frames(nr_gframes);
> +
> +       /* No need for kzalloc as it is initialized in following hyercall

                                                                   hypercall

> +        * GNTTABOP_get_status_frames.
> +        */
> +       sframes = kmalloc(nr_sframes  * sizeof(uint64_t), GFP_ATOMIC);
> +       if (!sframes)
> +               return -ENOMEM;
> +
> +       getframes.dom        = DOMID_SELF;
> +       getframes.nr_frames  = nr_sframes;
> +       set_xen_guest_handle(getframes.frame_list, sframes);
> +
> +       rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
> +                                      &getframes, 1);
> +       if (rc == -ENOSYS) {
> +               kfree(sframes);
> +               return -ENOSYS;
> +       }
> +
> +       BUG_ON(rc || getframes.status);
> +
> +       rc = arch_gnttab_map_status(sframes, nr_sframes,
> +                                   
> nr_status_frames(gnttab_max_grant_frames()),
> +                                   &grstatus);
> +       BUG_ON(rc);
> +       kfree(sframes);
> +
> +       return 0;
> +}
> +
>  static int gnttab_map_status(unsigned int nr_gframes)
>  {
>         return gnttab_interface._gnttab_map_status(nr_gframes);
> @@ -666,6 +830,9 @@ static int gnttab_map(unsigned int start_idx, unsigned 
> int end_idx)
>                 return rc;
>         }
> 
> +       /* No need for kzalloc as it is initialized in following hyercall

"hypercall" again

Ian.



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