[PATCH v2 6/9] xen/gntdev: Add initial support for dma-buf UAPI

Oleksandr Andrushchenko
2018-06-01T11:41:29Z

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

Add UAPI and IOCTLs for dma-buf grant device driver extension:
the extension allows userspace processes and kernel modules to
use Xen backed dma-buf implementation. With this extension grant
references to the pages of an imported dma-buf can be exported
for other domain use and grant references coming from a foreign
domain can be converted into a local dma-buf for local export.
Implement basic initialization and stubs for Xen DMA buffers'
support.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
---
drivers/xen/Kconfig | 10 +++
drivers/xen/Makefile | 1 +
drivers/xen/gntdev-dmabuf.c | 75 +++++++++++++++++++
drivers/xen/gntdev-dmabuf.h | 41 +++++++++++
drivers/xen/gntdev.c | 142 ++++++++++++++++++++++++++++++++++++
include/uapi/xen/gntdev.h | 91 +++++++++++++++++++++++
6 files changed, 360 insertions(+)
create mode 100644 drivers/xen/gntdev-dmabuf.c
create mode 100644 drivers/xen/gntdev-dmabuf.h

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 39536ddfbce4..52d64e4b6b81 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -152,6 +152,16 @@ config XEN_GNTDEV
help
Allows userspace processes to use grants.

+config XEN_GNTDEV_DMABUF
+ bool "Add support for dma-buf grant access device driver extension"
+ depends on XEN_GNTDEV && XEN_GRANT_DMA_ALLOC && DMA_SHARED_BUFFER
+ help
+ Allows userspace processes and kernel modules to use Xen backed
+ dma-buf implementation. With this extension grant references to
+ the pages of an imported dma-buf can be exported for other domain
+ use and grant references coming from a foreign domain can be
+ converted into a local dma-buf for local export.
+
config XEN_GRANT_DEV_ALLOC
tristate "User-space grant reference allocator driver"
depends on XEN
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 3c87b0c3aca6..33afb7b2b227 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -41,5 +41,6 @@ obj-$(CONFIG_XEN_PVCALLS_BACKEND) += pvcalls-back.o
obj-$(CONFIG_XEN_PVCALLS_FRONTEND) += pvcalls-front.o
xen-evtchn-y := evtchn.o
xen-gntdev-y := gntdev.o
+xen-gntdev-$(CONFIG_XEN_GNTDEV_DMABUF) += gntdev-dmabuf.o
xen-gntalloc-y := gntalloc.o
xen-privcmd-y := privcmd.o
diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
new file mode 100644
index 000000000000..6bedd1387bd9
--- /dev/null
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Xen dma-buf functionality for gntdev.
+ *
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#include <linux/slab.h>
+
+#include "gntdev-dmabuf.h"
+
+struct gntdev_dmabuf_priv {
+ int dummy;
+};
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer export support. */
+/* ------------------------------------------------------------------ */
+
+/* ------------------------------------------------------------------ */
+/* Implementation of wait for exported DMA buffer to be released. */
+/* ------------------------------------------------------------------ */
+
+int gntdev_dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
+ int wait_to_ms)
+{
+ return -EINVAL;
+}
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer export support. */
+/* ------------------------------------------------------------------ */
+
+int gntdev_dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args)
+{
+ return -EINVAL;
+}
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer import support. */
+/* ------------------------------------------------------------------ */
+
+struct gntdev_dmabuf *
+gntdev_dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
+ int fd, int count, int domid)
+{
+ return ERR_PTR(-ENOMEM);
+}
+
+u32 *gntdev_dmabuf_imp_get_refs(struct gntdev_dmabuf *gntdev_dmabuf)
+{
+ return NULL;
+}
+
+int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd)
+{
+ return -EINVAL;
+}
+
+struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void)
+{
+ struct gntdev_dmabuf_priv *priv;
+
+ priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return ERR_PTR(-ENOMEM);
+
+ return priv;
+}
+
+void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv)
+{
+ kfree(priv);
+}
diff --git a/drivers/xen/gntdev-dmabuf.h b/drivers/xen/gntdev-dmabuf.h
new file mode 100644
index 000000000000..040b2de904ac
--- /dev/null
+++ b/drivers/xen/gntdev-dmabuf.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Xen dma-buf functionality for gntdev.
+ *
+ * Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
+ */
+
+#ifndef _GNTDEV_DMABUF_H
+#define _GNTDEV_DMABUF_H
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+
+struct gntdev_dmabuf_priv;
+struct gntdev_dmabuf;
+struct device;
+
+struct gntdev_dmabuf_export_args {
+ int dummy;
+};
+
+struct gntdev_dmabuf_priv *gntdev_dmabuf_init(void);
+
+void gntdev_dmabuf_fini(struct gntdev_dmabuf_priv *priv);
+
+int gntdev_dmabuf_exp_from_pages(struct gntdev_dmabuf_export_args *args);
+
+int gntdev_dmabuf_exp_wait_released(struct gntdev_dmabuf_priv *priv, int fd,
+ int wait_to_ms);
+
+struct gntdev_dmabuf *
+gntdev_dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
+ int fd, int count, int domid);
+
+u32 *gntdev_dmabuf_imp_get_refs(struct gntdev_dmabuf *gntdev_dmabuf);
+
+int gntdev_dmabuf_imp_release(struct gntdev_dmabuf_priv *priv, u32 fd);
+
+#endif
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 9813fc440c70..7d58dfb3e5e8 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -6,6 +6,7 @@
*
* Copyright (c) 2006-2007, D G Murray.
* (c) 2009 Gerd Hoffmann <kraxel@redhat.com>
+ * (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -50,6 +51,10 @@
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+#include "gntdev-dmabuf.h"
+#endif
+
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
"Gerd Hoffmann <kraxel@redhat.com>");
@@ -80,6 +85,10 @@ struct gntdev_priv {
/* Device for which DMA memory is allocated. */
struct device *dma_dev;
#endif
+
+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+ struct gntdev_dmabuf_priv *dmabuf_priv;
+#endif
};

struct unmap_notify {
@@ -615,6 +624,15 @@ static int gntdev_open(struct inode *inode, struct file *flip)
INIT_LIST_HEAD(&priv->freeable_maps);
mutex_init(&priv->lock);

+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+ priv->dmabuf_priv = gntdev_dmabuf_init();
+ if (IS_ERR(priv->dmabuf_priv)) {
+ ret = PTR_ERR(priv->dmabuf_priv);
+ kfree(priv);
+ return ret;
+ }
+#endif
+
if (use_ptemod) {
priv->mm = get_task_mm(current);
if (!priv->mm) {
@@ -664,8 +682,13 @@ static int gntdev_release(struct inode *inode, struct file *flip)
WARN_ON(!list_empty(&priv->freeable_maps));
mutex_unlock(&priv->lock);

+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+ gntdev_dmabuf_fini(priv->dmabuf_priv);
+#endif
+
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
+
kfree(priv);
return 0;
}
@@ -1035,6 +1058,111 @@ static long gntdev_ioctl_grant_copy(struct gntdev_priv *priv, void __user *u)
return ret;
}

+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+/* ------------------------------------------------------------------ */
+/* DMA buffer export support. */
+/* ------------------------------------------------------------------ */
+
+int gntdev_dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags,
+ int count, u32 domid, u32 *refs, u32 *fd)
+{
+ /* XXX: this will need to work with gntdev's map, so leave it here. */
+ *fd = -1;
+ return -EINVAL;
+}
+
+/* ------------------------------------------------------------------ */
+/* DMA buffer IOCTL support. */
+/* ------------------------------------------------------------------ */
+
+static long
+gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_exp_from_refs __user *u)
+{
+ struct ioctl_gntdev_dmabuf_exp_from_refs op;
+ u32 *refs;
+ long ret;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
+ if (!refs)
+ return -ENOMEM;
+
+ if (copy_from_user(refs, u->refs, sizeof(*refs) * op.count) != 0) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ ret = gntdev_dmabuf_exp_from_refs(priv, op.flags, op.count,
+ op.domid, refs, &op.fd);
+ if (ret)
+ goto out;
+
+ if (copy_to_user(u, &op, sizeof(op)) != 0)
+ ret = -EFAULT;
+
+out:
+ kfree(refs);
+ return ret;
+}
+
+static long
+gntdev_ioctl_dmabuf_exp_wait_released(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_exp_wait_released __user *u)
+{
+ struct ioctl_gntdev_dmabuf_exp_wait_released op;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ return gntdev_dmabuf_exp_wait_released(priv->dmabuf_priv, op.fd,
+ op.wait_to_ms);
+}
+
+static long
+gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_imp_to_refs __user *u)
+{
+ struct ioctl_gntdev_dmabuf_imp_to_refs op;
+ struct gntdev_dmabuf *gntdev_dmabuf;
+ long ret;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ gntdev_dmabuf = gntdev_dmabuf_imp_to_refs(priv->dmabuf_priv,
+ priv->dma_dev, op.fd,
+ op.count, op.domid);
+ if (IS_ERR(gntdev_dmabuf))
+ return PTR_ERR(gntdev_dmabuf);
+
+ if (copy_to_user(u->refs, gntdev_dmabuf_imp_get_refs(gntdev_dmabuf),
+ sizeof(*u->refs) * op.count) != 0) {
+ ret = -EFAULT;
+ goto out_release;
+ }
+ return 0;
+
+out_release:
+ gntdev_dmabuf_imp_release(priv->dmabuf_priv, op.fd);
+ return ret;
+}
+
+static long
+gntdev_ioctl_dmabuf_imp_release(struct gntdev_priv *priv,
+ struct ioctl_gntdev_dmabuf_imp_release __user *u)
+{
+ struct ioctl_gntdev_dmabuf_imp_release op;
+
+ if (copy_from_user(&op, u, sizeof(op)) != 0)
+ return -EFAULT;
+
+ return gntdev_dmabuf_imp_release(priv->dmabuf_priv, op.fd);
+}
+#endif
+
static long gntdev_ioctl(struct file *flip,
unsigned int cmd, unsigned long arg)
{
@@ -1057,6 +1185,20 @@ static long gntdev_ioctl(struct file *flip,
case IOCTL_GNTDEV_GRANT_COPY:
return gntdev_ioctl_grant_copy(priv, ptr);

+#ifdef CONFIG_XEN_GNTDEV_DMABUF
+ case IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS:
+ return gntdev_ioctl_dmabuf_exp_from_refs(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED:
+ return gntdev_ioctl_dmabuf_exp_wait_released(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_IMP_TO_REFS:
+ return gntdev_ioctl_dmabuf_imp_to_refs(priv, ptr);
+
+ case IOCTL_GNTDEV_DMABUF_IMP_RELEASE:
+ return gntdev_ioctl_dmabuf_imp_release(priv, ptr);
+#endif
+
default:
pr_debug("priv %p, unknown cmd %x\n", priv, cmd);
return -ENOIOCTLCMD;
diff --git a/include/uapi/xen/gntdev.h b/include/uapi/xen/gntdev.h
index 4b9d498a31d4..fe4423e518c6 100644
--- a/include/uapi/xen/gntdev.h
+++ b/include/uapi/xen/gntdev.h
@@ -5,6 +5,7 @@
* Interface to /dev/xen/gntdev.
*
* Copyright (c) 2007, D G Murray
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
@@ -215,4 +216,94 @@ struct ioctl_gntdev_grant_copy {
*/
#define GNTDEV_DMA_FLAG_COHERENT (1 << 1)

+/*
+ * Create a dma-buf [1] from grant references @refs of count @count provided
+ * by the foreign domain @domid with flags @flags.
+ *
+ * By default dma-buf is backed by system memory pages, but by providing
+ * one of the GNTDEV_DMA_FLAG_XXX flags it can also be created as
+ * a DMA write-combine or coherent buffer, e.g. allocated with dma_alloc_wc/
+ * dma_alloc_coherent.
+ *
+ * Returns 0 if dma-buf was successfully created and the corresponding
+ * dma-buf's file descriptor is returned in @fd.
+ *
+ * [1] Documentation/driver-api/dma-buf.rst
+ */
+
+#define IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS \
+ _IOC(_IOC_NONE, 'G', 9, \
+ sizeof(struct ioctl_gntdev_dmabuf_exp_from_refs))
+struct ioctl_gntdev_dmabuf_exp_from_refs {
+ /* IN parameters. */
+ /* Specific options for this dma-buf: see GNTDEV_DMA_FLAG_XXX. */
+ __u32 flags;
+ /* Number of grant references in @refs array. */
+ __u32 count;
+ /* OUT parameters. */
+ /* File descriptor of the dma-buf. */
+ __u32 fd;
+ /* The domain ID of the grant references to be mapped. */
+ __u32 domid;
+ /* Variable IN parameter. */
+ /* Array of grant references of size @count. */
+ __u32 refs[1];
+};
+
+/*
+ * This will block until the dma-buf with the file descriptor @fd is
+ * released. This is only valid for buffers created with
+ * IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS.
+ *
+ * If within @wait_to_ms milliseconds the buffer is not released
+ * then -ETIMEDOUT error is returned.
+ * If the buffer with the file descriptor @fd does not exist or has already
+ * been released, then -ENOENT is returned. For valid file descriptors
+ * this must not be treated as error.
+ */
+#define IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED \
+ _IOC(_IOC_NONE, 'G', 10, \
+ sizeof(struct ioctl_gntdev_dmabuf_exp_wait_released))
+struct ioctl_gntdev_dmabuf_exp_wait_released {
+ /* IN parameters */
+ __u32 fd;
+ __u32 wait_to_ms;
+};
+
+/*
+ * Import a dma-buf with file descriptor @fd and export granted references
+ * to the pages of that dma-buf into array @refs of size @count.
+ */
+#define IOCTL_GNTDEV_DMABUF_IMP_TO_REFS \
+ _IOC(_IOC_NONE, 'G', 11, \
+ sizeof(struct ioctl_gntdev_dmabuf_imp_to_refs))
+struct ioctl_gntdev_dmabuf_imp_to_refs {
+ /* IN parameters. */
+ /* File descriptor of the dma-buf. */
+ __u32 fd;
+ /* Number of grant references in @refs array. */
+ __u32 count;
+ /* The domain ID for which references to be granted. */
+ __u32 domid;
+ /* Reserved - must be zero. */
+ __u32 reserved;
+ /* OUT parameters. */
+ /* Array of grant references of size @count. */
+ __u32 refs[1];
+};
+
+/*
+ * This will close all references to the imported buffer with file descriptor
+ * @fd, so it can be released by the owner. This is only valid for buffers
+ * created with IOCTL_GNTDEV_DMABUF_IMP_TO_REFS.
+ */
+#define IOCTL_GNTDEV_DMABUF_IMP_RELEASE \
+ _IOC(_IOC_NONE, 'G', 12, \
+ sizeof(struct ioctl_gntdev_dmabuf_imp_release))
+struct ioctl_gntdev_dmabuf_imp_release {
+ /* IN parameters */
+ __u32 fd;
+ __u32 reserved;
+};
+
#endif /* __LINUX_PUBLIC_GNTDEV_H__ */
--
2.17.0