libgnttab: Add support for Linux dma-buf

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Bump gnttab library minor version to 3.

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Quoted 7 lines · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Quoted 3 lines

Bump gnttab library minor version to 3.

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Has the Linux side been merged yet?

Wei.

Quoted 8 lines · Wei Liu

Quoted 7 lines · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Quoted 4 lines

Quoted 3 lines

Bump gnttab library minor version to 3.

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Has the Linux side been merged yet?

It is going to be merged into Boris' staging for now and then eventually move into Xen tip's for-linus (Boris can tell more on that: Linux is already at rc6, so I think this can happen in the nearest future).

Given that Xen and Linux parts are actually independent, I decided to start upstreaming libgnttab changes now, allowing me to mature the code and address comments

Quoted 11 lines · Oleksandr Andrushchenko

Quoted 10 lines · Wei Liu

Quoted 9 lines · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Bump gnttab library minor version to 3.

Quoted 7 lines

Quoted 2 lines

Quoted 1 line

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Has the Linux side been merged yet?

It is going to be merged into Boris' staging for now and then eventually move into Xen tip's for-linus (Boris can tell more on that: Linux is already at rc6, so I think this can happen in the nearest future).

OK. So the interfaces on Linux's side are agreed.

Quoted 4 lines

Given that Xen and Linux parts are actually independent, I decided to start upstreaming libgnttab changes now, allowing me to mature the code and address comments

From my PoV this patch provides a bunch of wrappers around Linux ioctls
so I would like to be sure the underlying interfaces are agreed before reviewing.

Wei.

Quoted 15 lines · Wei Liu

Quoted 14 lines · Oleksandr Andrushchenko

Quoted 13 lines · Wei Liu

Quoted 11 lines · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Bump gnttab library minor version to 3.

Signed-off-by: Oleksandr Andrushchenko
<[email protected]>

Quoted 7 lines

Quoted 6 lines

Quoted 1 line

Has the Linux side been merged yet?

It is going to be merged into Boris' staging for now and then eventually move into Xen tip's for-linus (Boris can tell more on that: Linux is already at rc6, so I think this can happen in the nearest future).

OK. So the interfaces on Linux's side are agreed.

Yes

Quoted 4 lines

Quoted 4 lines

Given that Xen and Linux parts are actually independent, I decided to start upstreaming libgnttab changes now, allowing me to mature the code and address comments

Quoted 3 lines

 From my PoV this patch provides a bunch of wrappers around Linux ioctls so I would like to be sure the underlying interfaces are agreed before reviewing.

Fair enough,
Boris could you please estimate when the corresponding Linux changes have a chance to get into Xen tip Linux tree?

Quoted 7 lines · Oleksandr Andrushchenko

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Quoted 3 lines

Bump gnttab library minor version to 3.

Signed-off-by Oleksandr Andrushchenko <[email protected]>

Has the Linux side been merged yet?

Wei.

From: Oleksandr Andrushchenko <[email protected]>

Add support for Linux grant device driver extension which allows converting existing dma-buf's into an array of grant references and vise versa. This is only implemented for Linux as other OSes have no Linux dma-buf support.

Bump gnttab library minor version to 3.

Signed-off-by Oleksandr Andrushchenko <[email protected]>

---
  tools/include/xen-sys/Linux/gntdev.h  | 106 ++++++++++++++++++++++++
  tools/libs/gnttab/Makefile            |   2 +-
  tools/libs/gnttab/gnttab_core.c       |  26 ++++++
  tools/libs/gnttab/gnttab_unimp.c      |  26 ++++++
  tools/libs/gnttab/include/xengnttab.h |  61 ++++++++++++++
  tools/libs/gnttab/libxengnttab.map    |   8 ++
  tools/libs/gnttab/linux.c             | 113 ++++++++++++++++++++++++++
  tools/libs/gnttab/minios.c            |  26 ++++++
  tools/libs/gnttab/private.h           |  13 +++
  9 files changed, 380 insertions(+), 1 deletion(-)

tools/include/xen-sys/Linux/gntdev.h +106 -0

index 0ca07c92b21c..d16076044c71 100644
@@ -4,6 +4,7 @@
   * 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

@@ -168,4 +169,109 @@ struct ioctl_gntdev_grant_copy {
      struct ioctl_gntdev_grant_copy_segment *segments;
  };
 
+/*
+ * Flags to be used while requesting memory mapping's backing storage
+ * to be allocated with DMA API.
+ */
+
+/*
+ * The buffer is backed with memory allocated with dma_alloc_wc.
+ */
+#define GNTDEV_DMA_FLAG_WC		(1 << 0)
+
+/*
+ * The buffer is backed with memory allocated with dma_alloc_coherent.
+ */
+#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] https://elixir.bootlin.com/linux/latest/source/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_DMABUF_FLAG_XXX. */
+    uint32_t flags;
+    /* Number of grant references in @refs array. */
+    uint32_t count;
+    /* OUT parameters. */
+    /* File descriptor of the dma-buf. */
+    uint32_t fd;
+    /* The domain ID of the grant references to be mapped. */
+    uint32_t domid;
+    /* Variable IN parameter. */
+    /* Array of grant references of size @count. */
+    uint32_t 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 withing @wait_to_ms milliseconds the buffer is not released
+ * then -ETIMEDOUT error is returned.
+ * If the buffer with 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 */
+    uint32_t fd;
+    uint32_t 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. */
+    uint32_t fd;
+    /* Number of grant references in @refs array. */
+    uint32_t count;
+    /* The domain ID for which references to be granted. */
+    uint32_t domid;
+    /* Reserved - must be zero. */
+    uint32_t reserved;
+    /* OUT parameters. */
+    /* Array of grant references of size @count. */
+    uint32_t refs[1];
+};
+
+/*
+ * This will close all references to an imported buffer, 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 */
+    uint32_t fd;
+    uint32_t reserved;
+};
+
  #endif /* __LINUX_PUBLIC_GNTDEV_H__ */

tools/libs/gnttab/Makefile +1 -1

index 6c2e7e36a2c3..0befbd18f1af 100644
@@ -2,7 +2,7 @@ XEN_ROOT = $(CURDIR)/../../..
  include $(XEN_ROOT)/tools/Rules.mk
 
  MAJOR    = 1
-MINOR    = 2
+MINOR    = 3
  SHLIB_LDFLAGS += -Wl,--version-script=libxengnttab.map
 
  CFLAGS   += -Werror -Wmissing-prototypes

tools/libs/gnttab/gnttab_core.c +26 -0

index bd075f818aa6..92e7228a2671 100644
@@ -1,6 +1,7 @@
  /******************************************************************************
   *
   * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public

@@ -134,6 +135,31 @@ int xengnttab_grant_copy(xengnttab_handle *xgt,
  {
      return osdep_gnttab_grant_copy(xgt, count, segs);
  }
+
+int xengnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                   uint32_t flags, uint32_t count,
+                                   const uint32_t *refs, uint32_t *fd)
+{
+    return osdep_gnttab_dmabuf_exp_from_refs(xgt, domid, flags, count,
+                                             refs, fd);
+}
+
+int xengnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt, uint32_t fd,
+                                       uint32_t wait_to_ms)
+{
+    return osdep_gnttab_dmabuf_exp_wait_released(xgt, fd, wait_to_ms);
+}
+
+int xengnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                 uint32_t fd, uint32_t count, uint32_t *refs)
+{
+    return osdep_gnttab_dmabuf_imp_to_refs(xgt, domid, fd, count, refs);
+}
+
+int xengnttab_dmabuf_imp_release(xengnttab_handle *xgt, uint32_t fd)
+{
+    return osdep_gnttab_dmabuf_imp_release(xgt, fd);
+}
  /*
   * Local variables:
   * mode: C

tools/libs/gnttab/gnttab_unimp.c +26 -0

index 26e4ee129d03..dee1afd2647f 100644
@@ -1,6 +1,7 @@
  /******************************************************************************
   *
   * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public

@@ -84,6 +85,31 @@ int xengnttab_grant_copy(xengnttab_handle *xgt,
  {
      abort();
  }
+
+int xengnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                   uint32_t flags, uint32_t count,
+                                   const uint32_t *refs, uint32_t *fd)
+{
+    abort();
+}
+
+int xengnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt, uint32_t fd,
+                                       uint32_t wait_to_ms)
+{
+    abort();
+}
+
+int xengnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                 uint32_t fd, uint32_t count, uint32_t *refs)
+{
+    abort();
+}
+
+int xengnttab_dmabuf_imp_release(xengnttab_handle *xgt, uint32_t fd)
+{
+    abort();
+}
+
  /*
   * Local variables:
   * mode: C

tools/libs/gnttab/include/xengnttab.h +61 -0

index 91d4cd5bdd88..111fc88caeb3 100644
@@ -18,6 +18,7 @@
   * A library for low-level access to the Xen control interfaces.
   *
   * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
   */
  #ifndef XENGNTTAB_H
  #define XENGNTTAB_H

@@ -295,6 +296,66 @@ int xengnttab_grant_copy(xengnttab_handle *xgt,
                           uint32_t count,
                           xengnttab_grant_copy_segment_t *segs);
 
+/*
+ * Flags to be used while requesting memory mapping's backing storage
+ * to be allocated with DMA API.
+ */
+
+/*
+ * The buffer is backed with memory allocated with dma_alloc_wc.
+ */
+#define GNTDEV_DMA_FLAG_WC		(1 << 0)
+
+/*
+ * The buffer is backed with memory allocated with dma_alloc_coherent.
+ */
+#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.
+ *
+ * Returns 0 if dma-buf was successfully created and the corresponding
+ * dma-buf's file descriptor is returned in @fd.
+ *
+ * [1] https://elixir.bootlin.com/linux/latest/source/Documentation/driver-api/dma-buf.rst
+ */
+int xengnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                   uint32_t flags, uint32_t count,
+                                   const uint32_t *refs, uint32_t *fd);
+
+/*
+ * 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 withing @wait_to_ms milliseconds the buffer is not released
+ * then -ETIMEDOUT error is returned.
+ * If the buffer with 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.
+ */
+int xengnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt, uint32_t fd,
+                                       uint32_t 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.
+ */
+int xengnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                 uint32_t fd, uint32_t count, uint32_t *refs);
+
+/*
+ * This will close all references to an imported buffer, so it can be
+ * released by the owner. This is only valid for buffers created with
+ * IOCTL_GNTDEV_DMABUF_IMP_TO_REFS.
+ */
+int xengnttab_dmabuf_imp_release(xengnttab_handle *xgt, uint32_t fd);
+
  /*
   * Grant Sharing Interface (allocating and granting pages to others)
   */

tools/libs/gnttab/libxengnttab.map +8 -0

index d5da388a0d8d..9de2183810a9 100644
@@ -32,3 +32,11 @@ VERS_1.2 {
  		xengnttab_fd;
  		xengntshr_fd;
  } VERS_1.1;
+
+VERS_1.3 {
+	global:
+		xengnttab_dmabuf_exp_from_refs;
+		xengnttab_dmabuf_exp_wait_released;
+		xengnttab_dmabuf_imp_to_refs;
+		xengnttab_dmabuf_imp_release;
+} VERS_1.2;

tools/libs/gnttab/linux.c +113 -0

index 8347ddd3d9cf..9765146f7eb6 100644
@@ -1,5 +1,6 @@
  /*
   * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public

@@ -309,6 +310,118 @@ int osdep_gnttab_grant_copy(xengnttab_handle *xgt,
      return rc;
  }
 
+int osdep_gnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                      uint32_t flags, uint32_t count,
+                                      const uint32_t *refs,
+                                      uint32_t *dmabuf_fd)
+{
+    struct ioctl_gntdev_dmabuf_exp_from_refs *from_refs;
+    int rc = 0;
+
+    if ( !count )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
+    from_refs = malloc(sizeof(*from_refs) +
+                       (count - 1) * sizeof(from_refs->refs[0]));
+    if ( !from_refs )
+    {
+        errno = ENOMEM;
+        return -1;
+    }
+
+    from_refs->flags = flags;
+    from_refs->count = count;
+    from_refs->domid = domid;
+
+    memcpy(from_refs->refs, refs, count * sizeof(from_refs->refs[0]));
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS, from_refs)) )
+    {
+        GTERROR(xgt->logger, "ioctl DMABUF_EXP_FROM_REFS failed");
+        goto out;
+    }
+
+    *dmabuf_fd = from_refs->fd;
+
+out:
+    free(from_refs);
+    return rc;
+}
+
+int osdep_gnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt,
+                                          uint32_t fd, uint32_t wait_to_ms)
+{
+    struct ioctl_gntdev_dmabuf_exp_wait_released wait;
+    int rc;
+
+    wait.fd = fd;
+    wait.wait_to_ms = wait_to_ms;
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED, &wait)) ) {
+        if ( errno == ENOENT ) {
+            /* The buffer may have already been released. */
+            errno = 0;
+            rc = 0;
+        } else
+            GTERROR(xgt->logger, "ioctl DMABUF_EXP_WAIT_RELEASED failed");
+    }
+
+    return rc;
+}
+
+int osdep_gnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                    uint32_t fd, uint32_t count, uint32_t *refs)
+{
+    struct ioctl_gntdev_dmabuf_imp_to_refs *to_refs;
+    int rc = 0;
+
+    if ( !count )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
+    to_refs = malloc(sizeof(*to_refs) +
+                     (count - 1) * sizeof(to_refs->refs[0]));
+    if ( !to_refs )
+    {
+        errno = ENOMEM;
+        return -1;
+    }
+
+    to_refs->fd = fd;
+    to_refs->count = count;
+    to_refs->domid = domid;
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_IMP_TO_REFS, to_refs)) )
+    {
+        GTERROR(xgt->logger, "ioctl DMABUF_IMP_TO_REFS failed");
+        goto out;
+    }
+
+    memcpy(refs, to_refs->refs, count * sizeof(*refs));
+
+out:
+    free(to_refs);
+    return rc;
+}
+
+int osdep_gnttab_dmabuf_imp_release(xengnttab_handle *xgt, uint32_t fd)
+{
+    struct ioctl_gntdev_dmabuf_imp_release release;
+    int rc;
+
+    release.fd = fd;
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_IMP_RELEASE, &release)) )
+        GTERROR(xgt->logger, "ioctl DMABUF_IMP_RELEASE failed");
+
+    return rc;
+}
+
  int osdep_gntshr_open(xengntshr_handle *xgs)
  {
      int fd = open(DEVXEN "gntalloc", O_RDWR);

tools/libs/gnttab/minios.c +26 -0

index 0951bc9bac5b..f78caadd3043 100644
@@ -112,6 +112,32 @@ int osdep_gnttab_grant_copy(xengnttab_handle *xgt,
  {
      return -1;
  }
+
+int osdep_gnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                      uint32_t flags, uint32_t count,
+                                      const uint32_t *refs, uint32_t *fd)
+{
+    return -1;
+}
+
+int osdep_gnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt,
+                                          uint32_t fd, uint32_t wait_to_ms)
+{
+    return -1;
+}
+
+int osdep_gnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                    uint32_t fd, uint32_t count,
+                                    uint32_t *refs)
+{
+    return -1;
+}
+
+int osdep_gnttab_dmabuf_imp_release(xengnttab_handle *xgt, uint32_t fd)
+{
+    return -1;
+}
+
  /*
   * Local variables:
   * mode: C

tools/libs/gnttab/private.h +6 -0

index ed8df40def0d..c5e23639b141 100644
@@ -35,6 +35,19 @@ int osdep_gnttab_grant_copy(xengnttab_handle *xgt,
                              uint32_t count,
                              xengnttab_grant_copy_segment_t *segs);
 
+int osdep_gnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                      uint32_t flags, uint32_t count,
+                                      const uint32_t *refs, uint32_t *fd);
+
+int osdep_gnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt,
+                                          uint32_t fd, uint32_t wait_to_ms);

tools/libs/gnttab/linux.c +1 -0

index 8347ddd3d9cf..9765146f7eb6 100644
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public

tools/libs/gnttab/linux.c +29 -0

+    }
+
+    from_refs = malloc(sizeof(*from_refs) +
+                       (count - 1) * sizeof(from_refs->refs[0]));
+    if ( !from_refs )
+    {
+        errno = ENOMEM;
+        return -1;
+    }
+
+    from_refs->flags = flags;
+    from_refs->count = count;
+    from_refs->domid = domid;
+
+    memcpy(from_refs->refs, refs, count * sizeof(from_refs->refs[0]));
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS, from_refs)) )
+    {
+        GTERROR(xgt->logger, "ioctl DMABUF_EXP_FROM_REFS failed");
+        goto out;
+    }
+
+    *dmabuf_fd = from_refs->fd;
+
+out:
+    free(from_refs);
+    return rc;
+}
+

tools/libs/gnttab/linux.c +10 -0

+            /* The buffer may have already been released. */
+            errno = 0;
+            rc = 0;
+        } else
+            GTERROR(xgt->logger, "ioctl DMABUF_EXP_WAIT_RELEASED failed");
+    }
+
+    return rc;
+}
+

On Mon, Jul 23, 2018 at 03:27:25PM +0300, Oleksandr Andrushchenko wrote:
[...]

Quoted 12 lines

tools/libs/gnttab/linux.c +1 -0

index 8347ddd3d9cf..9765146f7eb6 100644
@@ -1,5 +1,6 @@
  /*
   * Copyright (c) 2007-2008, D G Murray <[email protected]>
+ * Copyright (c) 2018, Oleksandr Andrushchenko, EPAM Systems Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public

tools/libs/gnttab/linux.c int osdep_gnttab_grant_copy(xengnttab_handle *xgt, · line 318

Quoted 9 lines

tools/libs/gnttab/linux.c +6 -0

@@ -309,6 +310,118 @@ int osdep_gnttab_grant_copy(xengnttab_handle *xgt,
      return rc;
  }
 
+int osdep_gnttab_dmabuf_exp_from_refs(xengnttab_handle *xgt, uint32_t domid,
+                                      uint32_t flags, uint32_t count,
+                                      const uint32_t *refs,
+                                      uint32_t *dmabuf_fd)
+{
+    struct ioctl_gntdev_dmabuf_exp_from_refs *from_refs;

You can set from_refs to NULL here, then ...

tools/libs/gnttab/linux.c int osdep_gnttab_grant_copy(xengnttab_handle *xgt, · line 324

Quoted 6 lines

tools/libs/gnttab/linux.c +6 -0

+    int rc = 0;
+
+    if ( !count )
+    {
+        errno = EINVAL;
+        return -1;

     rc = -1;
     goto out;

in all exit paths.

I don't like using two error handling styles. So please either change to use goto only or delete the only goto in this function.

Quoted 29 lines

tools/libs/gnttab/linux.c +29 -0

+    }
+
+    from_refs = malloc(sizeof(*from_refs) +
+                       (count - 1) * sizeof(from_refs->refs[0]));
+    if ( !from_refs )
+    {
+        errno = ENOMEM;
+        return -1;
+    }
+
+    from_refs->flags = flags;
+    from_refs->count = count;
+    from_refs->domid = domid;
+
+    memcpy(from_refs->refs, refs, count * sizeof(from_refs->refs[0]));
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_EXP_FROM_REFS, from_refs)) )
+    {
+        GTERROR(xgt->logger, "ioctl DMABUF_EXP_FROM_REFS failed");
+        goto out;
+    }
+
+    *dmabuf_fd = from_refs->fd;
+
+out:
+    free(from_refs);
+    return rc;
+}
+

tools/libs/gnttab/linux.c int osdep_gnttab_grant_copy(xengnttab_handle *xgt, · line 363

Quoted 10 lines

tools/libs/gnttab/linux.c +10 -0

+int osdep_gnttab_dmabuf_exp_wait_released(xengnttab_handle *xgt,
+                                          uint32_t fd, uint32_t wait_to_ms)
+{
+    struct ioctl_gntdev_dmabuf_exp_wait_released wait;
+    int rc;
+
+    wait.fd = fd;
+    wait.wait_to_ms = wait_to_ms;
+
+    if ( (rc = ioctl(xgt->fd, IOCTL_GNTDEV_DMABUF_EXP_WAIT_RELEASED, &wait)) ) {

{ should be on a new line.

tools/libs/gnttab/linux.c int osdep_gnttab_grant_copy(xengnttab_handle *xgt, · line 364

Quoted 1 line

tools/libs/gnttab/linux.c +1 -0

+        if ( errno == ENOENT ) {

Ditto.

Quoted 10 lines

tools/libs/gnttab/linux.c +10 -0

+            /* The buffer may have already been released. */
+            errno = 0;
+            rc = 0;
+        } else
+            GTERROR(xgt->logger, "ioctl DMABUF_EXP_WAIT_RELEASED failed");
+    }
+
+    return rc;
+}
+

tools/libs/gnttab/linux.c int osdep_gnttab_grant_copy(xengnttab_handle *xgt, · line 384

Quoted 10 lines

tools/libs/gnttab/linux.c +10 -0

+int osdep_gnttab_dmabuf_imp_to_refs(xengnttab_handle *xgt, uint32_t domid,
+                                    uint32_t fd, uint32_t count, uint32_t *refs)
+{
+    struct ioctl_gntdev_dmabuf_imp_to_refs *to_refs;
+    int rc = 0;
+
+    if ( !count )
+    {
+        errno = EINVAL;
+        return -1;

Same comments on error handling apply to this function too.

The rest looks fine.

Wei.