Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 551 insertions, 0 deletions

diff --git a/drivers/xen/xen-front-pgdir-shbuf.c b/drivers/xen/xen-front-pgdir-shbuf.c
new file mode 100644
index 000000000..b52e0fa59
--- /dev/null
+++ b/drivers/xen/xen-front-pgdir-shbuf.c
@@ -0,0 +1,551 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ * Xen frontend/backend page directory based shared buffer
+ * helper module.
+ *
+ * Copyright (C) 2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+
+#include <asm/xen/hypervisor.h>
+#include <xen/balloon.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/interface/io/ring.h>
+
+#include <xen/xen-front-pgdir-shbuf.h>
+
+/**
+ * This structure represents the structure of a shared page
+ * that contains grant references to the pages of the shared
+ * buffer. This structure is common to many Xen para-virtualized
+ * protocols at include/xen/interface/io/
+ */
+struct xen_page_directory {
+	grant_ref_t gref_dir_next_page;
+#define XEN_GREF_LIST_END	0
+	grant_ref_t gref[]; /* Variable length */
+};
+
+/**
+ * Shared buffer ops which are differently implemented
+ * depending on the allocation mode, e.g. if the buffer
+ * is allocated by the corresponding backend or frontend.
+ * Some of the operations.
+ */
+struct xen_front_pgdir_shbuf_ops {
+	/*
+	 * Calculate number of grefs required to handle this buffer,
+	 * e.g. if grefs are required for page directory only or the buffer
+	 * pages as well.
+	 */
+	void (*calc_num_grefs)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Fill page directory according to para-virtual display protocol. */
+	void (*fill_page_dir)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Claim grant references for the pages of the buffer. */
+	int (*grant_refs_for_buffer)(struct xen_front_pgdir_shbuf *buf,
+				     grant_ref_t *priv_gref_head, int gref_idx);
+
+	/* Map grant references of the buffer. */
+	int (*map)(struct xen_front_pgdir_shbuf *buf);
+
+	/* Unmap grant references of the buffer. */
+	int (*unmap)(struct xen_front_pgdir_shbuf *buf);
+};
+
+/**
+ * Get granted reference to the very first page of the
+ * page directory. Usually this is passed to the backend,
+ * so it can find/fill the grant references to the buffer's
+ * pages.
+ *
+ * \param buf shared buffer which page directory is of interest.
+ * \return granted reference to the very first page of the
+ * page directory.
+ */
+grant_ref_t
+xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf)
+{
+	if (!buf->grefs)
+		return INVALID_GRANT_REF;
+
+	return buf->grefs[0];
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_get_dir_start);
+
+/**
+ * Map granted references of the shared buffer.
+ *
+ * Depending on the shared buffer mode of allocation
+ * (be_alloc flag) this can either do nothing (for buffers
+ * shared by the frontend itself) or map the provided granted
+ * references onto the backing storage (buf->pages).
+ *
+ * \param buf shared buffer which grants to be mapped.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->ops && buf->ops->map)
+		return buf->ops->map(buf);
+
+	/* No need to map own grant references. */
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_map);
+
+/**
+ * Unmap granted references of the shared buffer.
+ *
+ * Depending on the shared buffer mode of allocation
+ * (be_alloc flag) this can either do nothing (for buffers
+ * shared by the frontend itself) or unmap the provided granted
+ * references.
+ *
+ * \param buf shared buffer which grants to be unmapped.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->ops && buf->ops->unmap)
+		return buf->ops->unmap(buf);
+
+	/* No need to unmap own grant references. */
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_unmap);
+
+/**
+ * Free all the resources of the shared buffer.
+ *
+ * \param buf shared buffer which resources to be freed.
+ */
+void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf)
+{
+	if (buf->grefs) {
+		int i;
+
+		for (i = 0; i < buf->num_grefs; i++)
+			if (buf->grefs[i] != INVALID_GRANT_REF)
+				gnttab_end_foreign_access(buf->grefs[i], NULL);
+	}
+	kfree(buf->grefs);
+	kfree(buf->directory);
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_free);
+
+/*
+ * Number of grefs a page can hold with respect to the
+ * struct xen_page_directory header.
+ */
+#define XEN_NUM_GREFS_PER_PAGE ((PAGE_SIZE - \
+				 offsetof(struct xen_page_directory, \
+					  gref)) / sizeof(grant_ref_t))
+
+/**
+ * Get the number of pages the page directory consumes itself.
+ *
+ * \param buf shared buffer.
+ */
+static int get_num_pages_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	return DIV_ROUND_UP(buf->num_pages, XEN_NUM_GREFS_PER_PAGE);
+}
+
+/**
+ * Calculate the number of grant references needed to share the buffer
+ * and its pages when backend allocates the buffer.
+ *
+ * \param buf shared buffer.
+ */
+static void backend_calc_num_grefs(struct xen_front_pgdir_shbuf *buf)
+{
+	/* Only for pages the page directory consumes itself. */
+	buf->num_grefs = get_num_pages_dir(buf);
+}
+
+/**
+ * Calculate the number of grant references needed to share the buffer
+ * and its pages when frontend allocates the buffer.
+ *
+ * \param buf shared buffer.
+ */
+static void guest_calc_num_grefs(struct xen_front_pgdir_shbuf *buf)
+{
+	/*
+	 * Number of pages the page directory consumes itself
+	 * plus grefs for the buffer pages.
+	 */
+	buf->num_grefs = get_num_pages_dir(buf) + buf->num_pages;
+}
+
+#define xen_page_to_vaddr(page) \
+	((uintptr_t)pfn_to_kaddr(page_to_xen_pfn(page)))
+
+/**
+ * Unmap the buffer previously mapped with grant references
+ * provided by the backend.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int backend_unmap(struct xen_front_pgdir_shbuf *buf)
+{
+	struct gnttab_unmap_grant_ref *unmap_ops;
+	int i, ret;
+
+	if (!buf->pages || !buf->backend_map_handles || !buf->grefs)
+		return 0;
+
+	unmap_ops = kcalloc(buf->num_pages, sizeof(*unmap_ops),
+			    GFP_KERNEL);
+	if (!unmap_ops)
+		return -ENOMEM;
+
+	for (i = 0; i < buf->num_pages; i++) {
+		phys_addr_t addr;
+
+		addr = xen_page_to_vaddr(buf->pages[i]);
+		gnttab_set_unmap_op(&unmap_ops[i], addr, GNTMAP_host_map,
+				    buf->backend_map_handles[i]);
+	}
+
+	ret = gnttab_unmap_refs(unmap_ops, NULL, buf->pages,
+				buf->num_pages);
+
+	for (i = 0; i < buf->num_pages; i++) {
+		if (unlikely(unmap_ops[i].status != GNTST_okay))
+			dev_err(&buf->xb_dev->dev,
+				"Failed to unmap page %d: %d\n",
+				i, unmap_ops[i].status);
+	}
+
+	if (ret)
+		dev_err(&buf->xb_dev->dev,
+			"Failed to unmap grant references, ret %d", ret);
+
+	kfree(unmap_ops);
+	kfree(buf->backend_map_handles);
+	buf->backend_map_handles = NULL;
+	return ret;
+}
+
+/**
+ * Map the buffer with grant references provided by the backend.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int backend_map(struct xen_front_pgdir_shbuf *buf)
+{
+	struct gnttab_map_grant_ref *map_ops = NULL;
+	unsigned char *ptr;
+	int ret, cur_gref, cur_dir_page, cur_page, grefs_left;
+
+	map_ops = kcalloc(buf->num_pages, sizeof(*map_ops), GFP_KERNEL);
+	if (!map_ops)
+		return -ENOMEM;
+
+	buf->backend_map_handles = kcalloc(buf->num_pages,
+					   sizeof(*buf->backend_map_handles),
+					   GFP_KERNEL);
+	if (!buf->backend_map_handles) {
+		kfree(map_ops);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Read page directory to get grefs from the backend: for external
+	 * buffer we only allocate buf->grefs for the page directory,
+	 * so buf->num_grefs has number of pages in the page directory itself.
+	 */
+	ptr = buf->directory;
+	grefs_left = buf->num_pages;
+	cur_page = 0;
+	for (cur_dir_page = 0; cur_dir_page < buf->num_grefs; cur_dir_page++) {
+		struct xen_page_directory *page_dir =
+			(struct xen_page_directory *)ptr;
+		int to_copy = XEN_NUM_GREFS_PER_PAGE;
+
+		if (to_copy > grefs_left)
+			to_copy = grefs_left;
+
+		for (cur_gref = 0; cur_gref < to_copy; cur_gref++) {
+			phys_addr_t addr;
+
+			addr = xen_page_to_vaddr(buf->pages[cur_page]);
+			gnttab_set_map_op(&map_ops[cur_page], addr,
+					  GNTMAP_host_map,
+					  page_dir->gref[cur_gref],
+					  buf->xb_dev->otherend_id);
+			cur_page++;
+		}
+
+		grefs_left -= to_copy;
+		ptr += PAGE_SIZE;
+	}
+	ret = gnttab_map_refs(map_ops, NULL, buf->pages, buf->num_pages);
+
+	/* Save handles even if error, so we can unmap. */
+	for (cur_page = 0; cur_page < buf->num_pages; cur_page++) {
+		if (likely(map_ops[cur_page].status == GNTST_okay)) {
+			buf->backend_map_handles[cur_page] =
+				map_ops[cur_page].handle;
+		} else {
+			buf->backend_map_handles[cur_page] =
+				INVALID_GRANT_HANDLE;
+			if (!ret)
+				ret = -ENXIO;
+			dev_err(&buf->xb_dev->dev,
+				"Failed to map page %d: %d\n",
+				cur_page, map_ops[cur_page].status);
+		}
+	}
+
+	if (ret) {
+		dev_err(&buf->xb_dev->dev,
+			"Failed to map grant references, ret %d", ret);
+		backend_unmap(buf);
+	}
+
+	kfree(map_ops);
+	return ret;
+}
+
+/**
+ * Fill page directory with grant references to the pages of the
+ * page directory itself.
+ *
+ * The grant references to the buffer pages are provided by the
+ * backend in this case.
+ *
+ * \param buf shared buffer.
+ */
+static void backend_fill_page_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	struct xen_page_directory *page_dir;
+	unsigned char *ptr;
+	int i, num_pages_dir;
+
+	ptr = buf->directory;
+	num_pages_dir = get_num_pages_dir(buf);
+
+	/* Fill only grefs for the page directory itself. */
+	for (i = 0; i < num_pages_dir - 1; i++) {
+		page_dir = (struct xen_page_directory *)ptr;
+
+		page_dir->gref_dir_next_page = buf->grefs[i + 1];
+		ptr += PAGE_SIZE;
+	}
+	/* Last page must say there is no more pages. */
+	page_dir = (struct xen_page_directory *)ptr;
+	page_dir->gref_dir_next_page = XEN_GREF_LIST_END;
+}
+
+/**
+ * Fill page directory with grant references to the pages of the
+ * page directory and the buffer we share with the backend.
+ *
+ * \param buf shared buffer.
+ */
+static void guest_fill_page_dir(struct xen_front_pgdir_shbuf *buf)
+{
+	unsigned char *ptr;
+	int cur_gref, grefs_left, to_copy, i, num_pages_dir;
+
+	ptr = buf->directory;
+	num_pages_dir = get_num_pages_dir(buf);
+
+	/*
+	 * While copying, skip grefs at start, they are for pages
+	 * granted for the page directory itself.
+	 */
+	cur_gref = num_pages_dir;
+	grefs_left = buf->num_pages;
+	for (i = 0; i < num_pages_dir; i++) {
+		struct xen_page_directory *page_dir =
+			(struct xen_page_directory *)ptr;
+
+		if (grefs_left <= XEN_NUM_GREFS_PER_PAGE) {
+			to_copy = grefs_left;
+			page_dir->gref_dir_next_page = XEN_GREF_LIST_END;
+		} else {
+			to_copy = XEN_NUM_GREFS_PER_PAGE;
+			page_dir->gref_dir_next_page = buf->grefs[i + 1];
+		}
+		memcpy(&page_dir->gref, &buf->grefs[cur_gref],
+		       to_copy * sizeof(grant_ref_t));
+		ptr += PAGE_SIZE;
+		grefs_left -= to_copy;
+		cur_gref += to_copy;
+	}
+}
+
+/**
+ * Grant references to the frontend's buffer pages.
+ *
+ * These will be shared with the backend, so it can
+ * access the buffer's data.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int guest_grant_refs_for_buffer(struct xen_front_pgdir_shbuf *buf,
+				       grant_ref_t *priv_gref_head,
+				       int gref_idx)
+{
+	int i, cur_ref, otherend_id;
+
+	otherend_id = buf->xb_dev->otherend_id;
+	for (i = 0; i < buf->num_pages; i++) {
+		cur_ref = gnttab_claim_grant_reference(priv_gref_head);
+		if (cur_ref < 0)
+			return cur_ref;
+
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id,
+						xen_page_to_gfn(buf->pages[i]),
+						0);
+		buf->grefs[gref_idx++] = cur_ref;
+	}
+	return 0;
+}
+
+/**
+ * Grant all the references needed to share the buffer.
+ *
+ * Grant references to the page directory pages and, if
+ * needed, also to the pages of the shared buffer data.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int grant_references(struct xen_front_pgdir_shbuf *buf)
+{
+	grant_ref_t priv_gref_head;
+	int ret, i, j, cur_ref;
+	int otherend_id, num_pages_dir;
+
+	ret = gnttab_alloc_grant_references(buf->num_grefs, &priv_gref_head);
+	if (ret < 0) {
+		dev_err(&buf->xb_dev->dev,
+			"Cannot allocate grant references\n");
+		return ret;
+	}
+
+	otherend_id = buf->xb_dev->otherend_id;
+	j = 0;
+	num_pages_dir = get_num_pages_dir(buf);
+	for (i = 0; i < num_pages_dir; i++) {
+		unsigned long frame;
+
+		cur_ref = gnttab_claim_grant_reference(&priv_gref_head);
+		if (cur_ref < 0)
+			return cur_ref;
+
+		frame = xen_page_to_gfn(virt_to_page(buf->directory +
+						     PAGE_SIZE * i));
+		gnttab_grant_foreign_access_ref(cur_ref, otherend_id, frame, 0);
+		buf->grefs[j++] = cur_ref;
+	}
+
+	if (buf->ops->grant_refs_for_buffer) {
+		ret = buf->ops->grant_refs_for_buffer(buf, &priv_gref_head, j);
+		if (ret)
+			return ret;
+	}
+
+	gnttab_free_grant_references(priv_gref_head);
+	return 0;
+}
+
+/**
+ * Allocate all required structures to mange shared buffer.
+ *
+ * \param buf shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+static int alloc_storage(struct xen_front_pgdir_shbuf *buf)
+{
+	buf->grefs = kcalloc(buf->num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
+	if (!buf->grefs)
+		return -ENOMEM;
+
+	buf->directory = kcalloc(get_num_pages_dir(buf), PAGE_SIZE, GFP_KERNEL);
+	if (!buf->directory)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/*
+ * For backend allocated buffers we don't need grant_refs_for_buffer
+ * as those grant references are allocated at backend side.
+ */
+static const struct xen_front_pgdir_shbuf_ops backend_ops = {
+	.calc_num_grefs = backend_calc_num_grefs,
+	.fill_page_dir = backend_fill_page_dir,
+	.map = backend_map,
+	.unmap = backend_unmap
+};
+
+/*
+ * For locally granted references we do not need to map/unmap
+ * the references.
+ */
+static const struct xen_front_pgdir_shbuf_ops local_ops = {
+	.calc_num_grefs = guest_calc_num_grefs,
+	.fill_page_dir = guest_fill_page_dir,
+	.grant_refs_for_buffer = guest_grant_refs_for_buffer,
+};
+
+/**
+ * Allocate a new instance of a shared buffer.
+ *
+ * \param cfg configuration to be used while allocating a new shared buffer.
+ * \return zero on success or a negative number on failure.
+ */
+int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg)
+{
+	struct xen_front_pgdir_shbuf *buf = cfg->pgdir;
+	int ret;
+
+	if (cfg->be_alloc)
+		buf->ops = &backend_ops;
+	else
+		buf->ops = &local_ops;
+	buf->xb_dev = cfg->xb_dev;
+	buf->num_pages = cfg->num_pages;
+	buf->pages = cfg->pages;
+
+	buf->ops->calc_num_grefs(buf);
+
+	ret = alloc_storage(buf);
+	if (ret)
+		goto fail;
+
+	ret = grant_references(buf);
+	if (ret)
+		goto fail;
+
+	buf->ops->fill_page_dir(buf);
+
+	return 0;
+
+fail:
+	xen_front_pgdir_shbuf_free(buf);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xen_front_pgdir_shbuf_alloc);
+
+MODULE_DESCRIPTION("Xen frontend/backend page directory based "
+		   "shared buffer handling");
+MODULE_AUTHOR("Oleksandr Andrushchenko");
+MODULE_LICENSE("GPL");