OSCL-LXR linux-6.0.1/​drivers/​xen/​xen-front-pgdir-shbuf.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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[1]; /* 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");

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