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