[Xen-devel] Re: [PATCH 2/3] libxc: add xc_gntshr_* functions

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Sep 01, 2011 at 12:22:17PM -0400, Daniel De Graaf wrote:
> These functions and the xc_gntshr device (/dev/xen/gntalloc on linux)
> allow applications to create pages shared with other domains.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> ---
>  tools/libxc/xc_gnttab.c      |   27 +++++++++
>  tools/libxc/xc_linux_osdep.c |  121 
> ++++++++++++++++++++++++++++++++++++++++++
>  tools/libxc/xc_private.c     |   13 +++++
>  tools/libxc/xenctrl.h        |   48 +++++++++++++++++
>  tools/libxc/xenctrlosdep.h   |   13 +++++
>  5 files changed, 222 insertions(+), 0 deletions(-)
> 
> diff --git a/tools/libxc/xc_gnttab.c b/tools/libxc/xc_gnttab.c
> index dc7aa0c..ffa3550 100644
> --- a/tools/libxc/xc_gnttab.c
> +++ b/tools/libxc/xc_gnttab.c
> @@ -204,6 +204,33 @@ int xc_gnttab_set_max_grants(xc_gnttab *xcg, uint32_t 
> count)
>       return xcg->ops->u.gnttab.set_max_grants(xcg, xcg->ops_handle, count);
>  }
>  
> +void *xc_gntshr_share_pages(xc_gntshr *xcg, uint32_t domid,
> +                            int count, uint32_t *refs, int writable)
> +{
> +     return xcg->ops->u.gntshr.share_pages(xcg, xcg->ops_handle, domid,
> +                                           count, refs, writable);
> +}
> +
> +void *xc_gntshr_share_page_notify(xc_gntshr *xcg, uint32_t domid,
> +                                  uint32_t *ref, int writable,
> +                                  uint32_t notify_offset,
> +                                  evtchn_port_t notify_port)
> +{
> +     return xcg->ops->u.gntshr.share_page_notify(xcg, xcg->ops_handle,
> +                     domid, ref, writable, notify_offset, notify_port);
> +}
> +
> +/*
> + * Unmaps the @count pages starting at @start_address, which were mapped by a
> + * call to xc_gntshr_share_*. Never logs.
> + */
> +int xc_gntshr_munmap(xc_gntshr *xcg, void *start_address, uint32_t count)
> +{
> +     return xcg->ops->u.gntshr.munmap(xcg, xcg->ops_handle,
> +                                      start_address, count);
> +}
> +
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
> index 8f7718f..871d37c 100644
> --- a/tools/libxc/xc_linux_osdep.c
> +++ b/tools/libxc/xc_linux_osdep.c
> @@ -34,6 +34,7 @@
>  #include <xen/memory.h>
>  #include <xen/sys/evtchn.h>
>  #include <xen/sys/gntdev.h>
> +#include <xen/sys/gntalloc.h>
>  
>  #include "xenctrl.h"
>  #include "xenctrlosdep.h"
> @@ -718,6 +719,124 @@ static struct xc_osdep_ops linux_gnttab_ops = {
>      },
>  };
>  
> +static xc_osdep_handle linux_gntshr_open(xc_gntshr *xcg)
> +{
> +    int fd = open(DEVXEN "gntalloc", O_RDWR);
> +
> +    if ( fd == -1 )
> +        return XC_OSDEP_OPEN_ERROR;
> +
> +    return (xc_osdep_handle)fd;
> +}
> +
> +static int linux_gntshr_close(xc_gntshr *xcg, xc_osdep_handle h)
> +{
> +    int fd = (int)h;
> +    return close(fd);
> +}
> +
> +static void *linux_gntshr_share_pages(xc_gntshr *xch, xc_osdep_handle h,
> +                                      uint32_t domid, int count,
> +                                      uint32_t *refs, int writable)
> +{
> +     struct ioctl_gntalloc_alloc_gref *gref_info = NULL;
> +     int err;
> +     void *area = NULL;
> +     gref_info = malloc(sizeof(*gref_info) + count * sizeof(uint32_t));
> +     if (!gref_info)
> +             return NULL;
> +     gref_info->domid = domid;
> +     gref_info->flags = writable ? GNTALLOC_FLAG_WRITABLE : 0;
> +     gref_info->count = count;
> +
> +     err = ioctl((int)h, IOCTL_GNTALLOC_ALLOC_GREF, gref_info);
> +     if (err) {
> +             PERROR("linux_gntshr_share_pages: ioctl failed");
> +             goto out;
> +     }
> +
> +     area = mmap(NULL, count * XC_PAGE_SIZE, PROT_READ | PROT_WRITE,
> +             MAP_SHARED, (int)h, gref_info->index);
> +
> +     if (area == MAP_FAILED) {
> +             area = NULL;
> +             PERROR("linux_gntshr_share_pages: mmap failed");
> +             goto out;
> +     }
> +
> +     memcpy(refs, gref_info->gref_ids, count * sizeof(uint32_t));
> + out:
> +     free(gref_info);
> +     return area;
> +}
> +
> +static void *linux_gntshr_share_page_notify(xc_gntshr *xch, xc_osdep_handle 
> h,
> +                                            uint32_t domid, uint32_t *ref,
> +                                            int writable, uint32_t 
> notify_offset,
> +                                            evtchn_port_t notify_port)
> +{
> +     struct ioctl_gntalloc_alloc_gref gref_info;
> +     struct ioctl_gntalloc_unmap_notify notify;
> +     int err;
> +     int fd = (int)h;
> +     void *area = NULL;
> +     gref_info.domid = domid;
> +     gref_info.flags = writable ? GNTALLOC_FLAG_WRITABLE : 0;
> +     gref_info.count = 1;
> +
> +     err = ioctl(fd, IOCTL_GNTALLOC_ALLOC_GREF, &gref_info);
> +     if (err) {
> +             PERROR("linux_gntshr_share_page_notify: ioctl failed");
> +             goto out;
> +     }
> +
> +     area = mmap(NULL, XC_PAGE_SIZE, PROT_READ | PROT_WRITE,
> +             MAP_SHARED, fd, gref_info.index);
> +
> +     if (area == MAP_FAILED) {
> +             PERROR("linux_gntshr_share_page_notify: mmap failed");
> +             area = NULL;
> +             goto out;
> +     }
> +
> +     notify.index = gref_info.index;
> +     notify.action = 0;
> +     if (notify_offset >= 0) {
> +             notify.index += notify_offset;
> +             notify.action |= UNMAP_NOTIFY_CLEAR_BYTE;
> +     }
> +     if (notify_port >= 0) {
> +             notify.event_channel_port = notify_port;
> +             notify.action |= UNMAP_NOTIFY_SEND_EVENT;
> +     }
> +     if (notify.action && ioctl(fd, IOCTL_GNTALLOC_SET_UNMAP_NOTIFY, 
> &notify)) {
> +             PERROR("linux_gntshr_share_page_notify: ioctl SET_UNMAP_NOTIFY 
> failed");

Should we report to the caller that we can't set it up? Say
by reporting via a bool (as in through the arguments )?

> +     }
> +
> +     *ref = gref_info.gref_ids[0];
> + out:
> +     return area;
> +}
> +
> +
> +static int linux_gntshr_munmap(xc_gntshr *xcg, xc_osdep_handle h,
> +                               void *start_address, uint32_t count)
> +{
> +     return munmap(start_address, count);
> +}
> +
> +static struct xc_osdep_ops linux_gntshr_ops = {
> +    .open = &linux_gntshr_open,
> +    .close = &linux_gntshr_close,
> +
> +    .u.gntshr = {
> +        .share_pages = &linux_gntshr_share_pages,
> +        .share_page_notify = &linux_gntshr_share_page_notify,
> +        .munmap = &linux_gntshr_munmap,
> +    },
> +};
> +
> +
>  static struct xc_osdep_ops *linux_osdep_init(xc_interface *xch, enum 
> xc_osdep_type type)
>  {
>      switch ( type )
> @@ -728,6 +847,8 @@ static struct xc_osdep_ops *linux_osdep_init(xc_interface 
> *xch, enum xc_osdep_ty
>          return &linux_evtchn_ops;
>      case XC_OSDEP_GNTTAB:
>          return &linux_gnttab_ops;
> +    case XC_OSDEP_GNTSHR:
> +        return &linux_gntshr_ops;
>      default:
>          return NULL;
>      }
> diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c
> index 09c8f23..09a91e7 100644
> --- a/tools/libxc/xc_private.c
> +++ b/tools/libxc/xc_private.c
> @@ -258,6 +258,19 @@ int xc_gnttab_close(xc_gnttab *xcg)
>      return xc_interface_close_common(xcg);
>  }
>  
> +xc_gntshr *xc_gntshr_open(xentoollog_logger *logger,
> +                             unsigned open_flags)
> +{
> +    return xc_interface_open_common(logger, NULL, open_flags,
> +                                    XC_OSDEP_GNTSHR);
> +}
> +
> +int xc_gntshr_close(xc_gntshr *xcg)
> +{
> +    return xc_interface_close_common(xcg);
> +}
> +
> +
>  static pthread_key_t errbuf_pkey;
>  static pthread_once_t errbuf_pkey_once = PTHREAD_ONCE_INIT;
>  
> diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
> index 7859571..374c705 100644
> --- a/tools/libxc/xenctrl.h
> +++ b/tools/libxc/xenctrl.h
> @@ -115,6 +115,7 @@
>  typedef struct xc_interface_core xc_interface;
>  typedef struct xc_interface_core xc_evtchn;
>  typedef struct xc_interface_core xc_gnttab;
> +typedef struct xc_interface_core xc_gntshr;
>  typedef enum xc_error_code xc_error_code;
>  
>  
> @@ -1400,6 +1401,53 @@ grant_entry_v1_t *xc_gnttab_map_table_v1(xc_interface 
> *xch, int domid, int *gnt_
>  grant_entry_v2_t *xc_gnttab_map_table_v2(xc_interface *xch, int domid, int 
> *gnt_num);
>  /* Sometimes these don't set errno [fixme], and sometimes they don't log. */
>  
> +/*
> + * Return an fd onto the grant sharing driver.  Logs errors.
> + */
> +xc_gntshr *xc_gntshr_open(xentoollog_logger *logger,
> +                       unsigned open_flags);
> +
> +/*
> + * Close a handle previously allocated with xc_gntshr_open().
> + * Never logs errors.
> + */
> +int xc_gntshr_close(xc_gntshr *xcg);
> +
> +/*
> + * Creates and shares pages with another domain.
> + * 
> + * @parm xcg a handle to an open grant sharing instance
> + * @parm domid the domain to share memory with
> + * @parm count the number of pages to share
> + * @parm refs the grant references of the pages (output)
> + * @parm writable true if the other domain can write to the pages
> + * @return local mapping of the pages
> + */
> +void *xc_gntshr_share_pages(xc_gntshr *xcg, uint32_t domid,
> +                            int count, uint32_t *refs, int writable);
> +
> +/*
> + * Creates and shares a page with another domain, with unmap notification.
> + * 
> + * @parm xcg a handle to an open grant sharing instance
> + * @parm domid the domain to share memory with
> + * @parm refs the grant reference of the pages (output)
> + * @parm writable true if the other domain can write to the page
> + * @parm notify_offset The byte offset in the page to use for unmap
> + *                     notification; -1 for none.
> + * @parm notify_port The event channel port to use for unmap notify, or -1
> + * @return local mapping of the page
> + */
> +void *xc_gntshr_share_page_notify(xc_gntshr *xcg, uint32_t domid,
> +                                  uint32_t *ref, int writable,
> +                                  uint32_t notify_offset,
> +                                  evtchn_port_t notify_port);
> +/*
> + * Unmaps the @count pages starting at @start_address, which were mapped by a
> + * call to xc_gntshr_share_*. Never logs.
> + */
> +int xc_gntshr_munmap(xc_gntshr *xcg, void *start_address, uint32_t count);
> +
>  int xc_physdev_map_pirq(xc_interface *xch,
>                          int domid,
>                          int index,
> diff --git a/tools/libxc/xenctrlosdep.h b/tools/libxc/xenctrlosdep.h
> index 01969c5..e1c1ba5 100644
> --- a/tools/libxc/xenctrlosdep.h
> +++ b/tools/libxc/xenctrlosdep.h
> @@ -54,6 +54,7 @@ enum xc_osdep_type {
>      XC_OSDEP_PRIVCMD,
>      XC_OSDEP_EVTCHN,
>      XC_OSDEP_GNTTAB,
> +    XC_OSDEP_GNTSHR,
>  };
>  
>  /* Opaque handle internal to the backend */
> @@ -129,6 +130,18 @@ struct xc_osdep_ops
>                            uint32_t count);
>              int (*set_max_grants)(xc_gnttab *xcg, xc_osdep_handle h, 
> uint32_t count);
>          } gnttab;
> +        struct {
> +            void *(*share_pages)(xc_gntshr *xcg, xc_osdep_handle h,
> +                                 uint32_t domid, int count,
> +                                 uint32_t *refs, int writable);
> +            void *(*share_page_notify)(xc_gntshr *xcg, xc_osdep_handle h,
> +                                       uint32_t domid,
> +                                       uint32_t *ref, int writable,
> +                                       uint32_t notify_offset,
> +                                       evtchn_port_t notify_port);
> +            int (*munmap)(xc_gntshr *xcg, xc_osdep_handle h,
> +                          void *start_address, uint32_t count);
> +        } gntshr;
>      } u;
>  };
>  typedef struct xc_osdep_ops xc_osdep_ops;
> -- 
> 1.7.6

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