Re: [Minios-devel] [UNIKRAFT PATCH v3 16/17] plat/xen/drivers/blk: Grant references support

[Costin Lupu <costin.lupu@xxxxxxxxx>]

Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>

On 10/30/19 5:55 PM, Roxana Nicolescu wrote:
> This patch introduces the functions used for allocating
> new grant references in order to share data for requests.
> 
> Signed-off-by: Roxana Nicolescu <nicolescu.roxana1996@xxxxxxxxx>
> ---
>  plat/xen/drivers/blk/blkfront.c | 92 +++++++++++++++++++++++++++++++++
>  plat/xen/drivers/blk/blkfront.h | 10 ++++
>  2 files changed, 102 insertions(+)
> 
> diff --git a/plat/xen/drivers/blk/blkfront.c b/plat/xen/drivers/blk/blkfront.c
> index 1b4d2938..d233dac8 100644
> --- a/plat/xen/drivers/blk/blkfront.c
> +++ b/plat/xen/drivers/blk/blkfront.c
> @@ -65,6 +65,87 @@
>  
>  static struct uk_alloc *drv_allocator;
>  
> +static int blkfront_request_set_grefs(struct blkfront_request *blkfront_req)
> +{
> +     struct blkfront_gref *ref_elem;
> +     uint16_t nb_segments;
> +     int grefi = 0, grefj;
> +     int err = 0;
> +
> +     UK_ASSERT(blkfront_req != NULL);
> +     nb_segments = blkfront_req->nb_segments;
> +
> +     /* we allocate new ones */
> +     for (; grefi < nb_segments; ++grefi) {
> +             ref_elem = uk_malloc(drv_allocator, sizeof(*ref_elem));
> +             if (!ref_elem) {
> +                     err = -ENOMEM;
> +                     goto err;
> +             }
> +
> +             blkfront_req->gref[grefi] = ref_elem;
> +     }
> +
> +out:
> +     return err;
> +err:
> +     /* Free all the elements from 0 index to where the error happens */
> +     for (grefj = 0; grefj < grefi; ++grefj) {
> +             ref_elem = blkfront_req->gref[grefj];
> +             uk_free(drv_allocator, ref_elem);
> +     }
> +     goto out;
> +}
> +
> +static void blkfront_request_reset_grefs(struct blkfront_request *req)
> +{
> +     uint16_t gref_id = 0;
> +     struct blkfront_gref *gref_elem;
> +     uint16_t nb_segments;
> +     int rc;
> +
> +     UK_ASSERT(req);
> +     nb_segments = req->nb_segments;
> +
> +     for (; gref_id < nb_segments; ++gref_id) {
> +             gref_elem = req->gref[gref_id];
> +             if (gref_elem->ref != GRANT_INVALID_REF) {
> +                     rc = gnttab_end_access(gref_elem->ref);
> +                     UK_ASSERT(rc);
> +             }
> +
> +             uk_free(drv_allocator, gref_elem);
> +     }
> +}
> +
> +static void blkfront_request_map_grefs(struct blkif_request *ring_req,
> +             domid_t otherend_id)
> +{
> +     uint16_t gref_index;
> +     struct blkfront_request *blkfront_req;
> +     struct uk_blkreq *req;
> +     uint16_t nb_segments;
> +     uintptr_t data;
> +     uintptr_t start_sector;
> +     struct blkfront_gref *ref_elem;
> +
> +     UK_ASSERT(ring_req);
> +
> +     blkfront_req = (struct blkfront_request *)ring_req->id;
> +     req = blkfront_req->req;
> +     start_sector = round_pgdown((uintptr_t)req->aio_buf);
> +     nb_segments = blkfront_req->nb_segments;
> +
> +     for (gref_index = 0; gref_index < nb_segments; ++gref_index) {
> +             data = start_sector + gref_index * PAGE_SIZE;
> +             ref_elem = blkfront_req->gref[gref_index];
> +             ref_elem->ref = gnttab_grant_access(otherend_id,
> +                             virtual_to_mfn(data), ring_req->operation);
> +
> +             UK_ASSERT(ref_elem->ref != GRANT_INVALID_REF);
> +             ring_req->seg[gref_index].gref = ref_elem->ref;
> +     }
> +}
>  
>  static void blkif_request_init(struct blkif_request *ring_req,
>               __sector sector_size)
> @@ -147,6 +228,15 @@ static int blkfront_request_write(struct 
> blkfront_request *blkfront_req,
>       blkif_request_init(ring_req, sector_size);
>       blkfront_req->nb_segments = ring_req->nr_segments;
>  
> +     /* Get blkfront_grefs from pool or allocate new ones */
> +     rc = blkfront_request_set_grefs(blkfront_req);
> +     if (rc)
> +             goto out;
> +
> +     /* Map grant references to ring_req */
> +     blkfront_request_map_grefs(ring_req, dev->xendev->otherend_id);
> +
> +out:
>       return rc;
>  }
>  
> @@ -318,9 +408,11 @@ static int blkfront_queue_dequeue(struct uk_blkdev_queue 
> *queue,
>       switch (rsp->operation) {
>       case BLKIF_OP_READ:
>               CHECK_STATUS(req_from_q, status, "read");
> +             blkfront_request_reset_grefs(blkfront_req);
>               break;
>       case BLKIF_OP_WRITE:
>               CHECK_STATUS(req_from_q, status, "write");
> +             blkfront_request_reset_grefs(blkfront_req);
>               break;
>       case BLKIF_OP_WRITE_BARRIER:
>               if (status != BLKIF_RSP_OKAY)
> diff --git a/plat/xen/drivers/blk/blkfront.h b/plat/xen/drivers/blk/blkfront.h
> index 93d2905d..9620a8d6 100644
> --- a/plat/xen/drivers/blk/blkfront.h
> +++ b/plat/xen/drivers/blk/blkfront.h
> @@ -47,12 +47,22 @@
>  #include <common/events.h>
>  
>  
> +/**
> + * Structure used to describe a grant ref element.
> + */
> +struct blkfront_gref {
> +     /* Grant ref number. */
> +     grant_ref_t ref;
> +};
> +
>  /**
>   * Structure used to describe a front device request.
>   */
>  struct blkfront_request {
>       /* Request from the API. */
>       struct uk_blkreq *req;
> +     /* List with maximum number of blkfront_grefs for a request. */
> +     struct blkfront_gref *gref[BLKIF_MAX_SEGMENTS_PER_REQUEST];
>       /* Number of segments. */
>       uint16_t nb_segments;
>       /* Queue in which the request will be stored */
> 

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