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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> +	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?)