Messages in this thread | | | Subject | Re: [Xen-devel][PATCH 1/3] xen: Introduce shared buffer helpers for page directory... | From | Oleksandr Andrushchenko <> | Date | Thu, 29 Nov 2018 13:22:01 +0200 |
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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_ */
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