[Xen-devel] Re: [PATCH 2/3] xen-fbfront: Use grant references when requested

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

> +     int be_id = dev->otherend_id;
> +     int i, ref;
> +     unsigned long mfn;
> +     grant_ref_t gref_head;
> +     int allpages = info->nr_pages + ((info->nr_pages + epd - 1) / epd) + 1;
> +
> +     int grants = 0;
> +     xenbus_scanf(XBT_NIL, dev->otherend, "feature-grants", "%d", &grants);
> +
> +     if (grants) {
> +             int err = gnttab_alloc_grant_references(allpages, &gref_head);
> +             if (err < 0) {
> +                     xenbus_dev_fatal(dev, err, "fbdev grant refs");
> +                     info->page_gref = -ENOSPC;
> +             } else {
> +                     ref = gnttab_claim_grant_reference(&gref_head);
> +                     mfn = virt_to_mfn(info->page);
> +                     BUG_ON(ref == -ENOSPC);
> +                     gnttab_grant_foreign_access_ref(ref, be_id, mfn, 0);
> +                     info->page_gref = ref;
> +             }
> +     } else
> +             info->page_gref = -ENOENT;
>  
>       for (i = 0; i < info->nr_pages; i++)
> -             info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
> +     {
> +             mfn = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
> +             if (grants) {
> +                     ref = gnttab_claim_grant_reference(&gref_head);
> +                     BUG_ON(ref == -ENOSPC);
> +                     gnttab_grant_foreign_access_ref(ref, be_id, mfn, 1);
> +                     info->mfns[i] = ref;
> +             } else
> +                     info->mfns[i] = mfn;
> +     }
>  
>       for (i = 0; i * epd < info->nr_pages; i++)
> -             info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
> +     {
> +             mfn = vmalloc_to_mfn(&info->mfns[i * epd]);
> +             if (grants) {
> +                     ref = gnttab_claim_grant_reference(&gref_head);
> +                     BUG_ON(ref == -ENOSPC);
> +                     gnttab_grant_foreign_access_ref(ref, be_id, mfn, 1);
> +                     info->page->pd[i] = ref;
> +             } else
> +                     info->page->pd[i] = mfn;
> +     }

Shouldn't we in xenfb_remove also cleanup (unclaim and wholesale free the
grant reference lot?)

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