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Message-ID: <0d5ae87a-be43-ce7c-57b2-4567bb7e9f4d@oracle.com>
Date: Wed, 20 Apr 2022 14:44:31 -0400
From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
To: Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
linux-kernel@...r.kernel.org
Cc: Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH 09/18] xen/xenbus: add xenbus_setup_ring() service
function
On 4/20/22 11:09 AM, Juergen Gross wrote:
>
> +/*
> + * xenbus_setup_ring
> + * @dev: xenbus device
> + * @vaddr: pointer to starting virtual address of the ring
> + * @nr_pages: number of pages to be granted
> + * @grefs: grant reference array to be filled in
> + *
> + * Allocate physically contiguous pages for a shared ring buffer and grant it
> + * to the peer of the given device. The ring buffer is initially filled with
> + * zeroes. The virtual address of the ring is stored at @vaddr and the
> + * grant references are stored in the @grefs array. In case of error @vaddr
> + * will be set to NULL and @grefs will be filled with INVALID_GRANT_REF.
> + */
> +int xenbus_setup_ring(struct xenbus_device *dev, gfp_t gfp, void **vaddr,
> + unsigned int nr_pages, grant_ref_t *grefs)
> +{
> + unsigned long ring_size = nr_pages * XEN_PAGE_SIZE;
> + unsigned int i;
> + int ret;
> +
> + *vaddr = alloc_pages_exact(ring_size, gfp | __GFP_ZERO);
> + if (!*vaddr) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + ret = xenbus_grant_ring(dev, *vaddr, nr_pages, grefs);
> + if (ret)
> + goto err;
> +
> + return 0;
> +
> + err:
> + if (*vaddr)
> + free_pages_exact(*vaddr, ring_size);
> + for (i = 0; i < nr_pages; i++)
> + grefs[i] = INVALID_GRANT_REF;
> + *vaddr = NULL;
> +
> + return ret;
> +}
We can create a wrapper around this function that will also call SHARED_RING_INIT() and FRONT_RING_INIT(). A bunch of drivers do that.
-boris
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