ping
On 11/22/18 12:02 PM, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
based frontends. Currently the frontends which implement similar code for sharing big buffers between frontend and backend are para-virtualized DRM and sound drivers. Both define the same way to share grant references of a data buffer with the corresponding backend with little differences.
Move shared code into a helper module, so there is a single implementation of the same functionality for all.
Signed-off-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
drivers/xen/Kconfig | 3 + drivers/xen/Makefile | 1 + drivers/xen/xen-front-pgdir-shbuf.c | 553 ++++++++++++++++++++++++++++ include/xen/xen-front-pgdir-shbuf.h | 89 +++++ 4 files changed, 646 insertions(+) create mode 100644 drivers/xen/xen-front-pgdir-shbuf.c create mode 100644 include/xen/xen-front-pgdir-shbuf.h
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index 815b9e9bb975..838b66a9a0e7 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -340,4 +340,7 @@ config XEN_SYMS config XEN_HAVE_VPMU bool
+config XEN_FRONT_PGDIR_SHBUF
- tristate
- endmenu
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile index 3e542f60f29f..c48927a58e10 100644 --- a/drivers/xen/Makefile +++ b/drivers/xen/Makefile @@ -44,3 +44,4 @@ xen-gntdev-y := gntdev.o xen-gntdev-$(CONFIG_XEN_GNTDEV_DMABUF) += gntdev-dmabuf.o xen-gntalloc-y := gntalloc.o xen-privcmd-y := privcmd.o privcmd-buf.o +obj-$(CONFIG_XEN_FRONT_PGDIR_SHBUF) += xen-front-pgdir-shbuf.o diff --git a/drivers/xen/xen-front-pgdir-shbuf.c b/drivers/xen/xen-front-pgdir-shbuf.c new file mode 100644 index 000000000000..48a658dc7ccf --- /dev/null +++ b/drivers/xen/xen-front-pgdir-shbuf.c @@ -0,0 +1,553 @@ +// 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>
+#ifndef GRANT_INVALID_REF +/*
- FIXME: usage of grant reference 0 as invalid grant reference:
- grant reference 0 is valid, but never exposed to a PV driver,
- because of the fact it is already in use/reserved by the PV console.
- */
+#define GRANT_INVALID_REF 0 +#endif
+/**
- 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;
- 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 GRANT_INVALID_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 maped.
- \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 unmaped.
- \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] != GRANT_INVALID_REF)gnttab_end_foreign_access(buf->grefs[i],0, 0UL);- }
- 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++) {
buf->backend_map_handles[cur_page] = map_ops[cur_page].handle;if (unlikely(map_ops[cur_page].status != GNTST_okay))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 = GRANT_INVALID_REF;
+}
+/**
- 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 = GRANT_INVALID_REF;} 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"); diff --git a/include/xen/xen-front-pgdir-shbuf.h b/include/xen/xen-front-pgdir-shbuf.h new file mode 100644 index 000000000000..150ef7ec51ec --- /dev/null +++ b/include/xen/xen-front-pgdir-shbuf.h @@ -0,0 +1,89 @@ +/* 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
- */
+#ifndef __XEN_FRONT_PGDIR_SHBUF_H_ +#define __XEN_FRONT_PGDIR_SHBUF_H_
+#include <linux/kernel.h>
+#include <xen/grant_table.h>
+struct xen_front_pgdir_shbuf_ops;
+struct xen_front_pgdir_shbuf {
- /*
* Number of references granted for the backend use:** - for frontend allocated/imported buffers this holds the number* of grant references for the page directory and the pages* of the buffer** - for the buffer provided by the backend this only holds the number* of grant references for the page directory itself as grant* references for the buffer will be provided by the backend.*/- int num_grefs;
- grant_ref_t *grefs;
- /* Page directory backing storage. */
- u8 *directory;
- /*
* Number of pages for the shared buffer itself (excluding the page* directory).*/- int num_pages;
- /*
* Backing storage of the shared buffer: these are the pages being* shared.*/- struct page **pages;
- struct xenbus_device *xb_dev;
- /* These are the ops used internally depending on be_alloc mode. */
- const struct xen_front_pgdir_shbuf_ops *ops;
- /* Xen map handles for the buffer allocated by the backend. */
- grant_handle_t *backend_map_handles;
+};
+struct xen_front_pgdir_shbuf_cfg {
- struct xenbus_device *xb_dev;
- /* Number of pages of the buffer backing storage. */
- int num_pages;
- /* Pages of the buffer to be shared. */
- struct page **pages;
- /*
* This is allocated outside because there are use-cases when* the buffer structure is allocated as a part of a bigger one.*/- struct xen_front_pgdir_shbuf *pgdir;
- /*
* Mode of grant reference sharing: if set then backend will share* grant references to the buffer with the frontend.*/- int be_alloc;
+};
+int xen_front_pgdir_shbuf_alloc(struct xen_front_pgdir_shbuf_cfg *cfg);
+grant_ref_t +xen_front_pgdir_shbuf_get_dir_start(struct xen_front_pgdir_shbuf *buf);
+int xen_front_pgdir_shbuf_map(struct xen_front_pgdir_shbuf *buf);
+int xen_front_pgdir_shbuf_unmap(struct xen_front_pgdir_shbuf *buf);
+void xen_front_pgdir_shbuf_free(struct xen_front_pgdir_shbuf *buf);
+#endif /* __XEN_FRONT_PGDIR_SHBUF_H_ */