[Xen-devel] [PATCH 1/3] libxc: add xc_gnttab_map_grant_ref_notify

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

Normally, when a userspace process mapping a grant crashes, the domain
providing the reference receives no indication that its peer has
crashed, possibly leading to unexpected freezes or timeouts. This
function provides a notification of the unmap by signalling an event
channel and/or clearing a specific byte in the page.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 tools/libxc/xc_gnttab.c      |   15 ++++++++++++
 tools/libxc/xc_linux_osdep.c |   52 ++++++++++++++++++++++++++++++++++++++++++
 tools/libxc/xenctrl.h        |   21 +++++++++++++++++
 tools/libxc/xenctrlosdep.h   |    5 ++++
 4 files changed, 93 insertions(+), 0 deletions(-)

diff --git a/tools/libxc/xc_gnttab.c b/tools/libxc/xc_gnttab.c
index 4f55fce..dc7aa0c 100644
--- a/tools/libxc/xc_gnttab.c
+++ b/tools/libxc/xc_gnttab.c
@@ -174,6 +174,21 @@ void *xc_gnttab_map_domain_grant_refs(xc_gnttab *xcg,
                                                        count, domid, refs, 
prot);
 }
 
+void *xc_gnttab_map_grant_ref_notify(xc_gnttab *xcg,
+                                     uint32_t domid,
+                                     uint32_t ref,
+                                     uint32_t notify_offset,
+                                     evtchn_port_t notify_port)
+{
+       if (xcg->ops->u.gnttab.map_grant_ref_notify)
+               return xcg->ops->u.gnttab.map_grant_ref_notify(xcg, 
xcg->ops_handle,
+                       domid, ref, notify_offset, notify_port);
+       else
+               return xcg->ops->u.gnttab.map_grant_ref(xcg, xcg->ops_handle,
+                       domid, ref, PROT_READ|PROT_WRITE);
+}
+
+
 int xc_gnttab_munmap(xc_gnttab *xcg,
                      void *start_address,
                      uint32_t count)
diff --git a/tools/libxc/xc_linux_osdep.c b/tools/libxc/xc_linux_osdep.c
index dca6718..8f7718f 100644
--- a/tools/libxc/xc_linux_osdep.c
+++ b/tools/libxc/xc_linux_osdep.c
@@ -613,6 +613,57 @@ static void *linux_gnttab_map_domain_grant_refs(xc_gnttab 
*xcg, xc_osdep_handle
     return do_gnttab_map_grant_refs(xcg, h, count, &domid, 0, refs, prot);
 }
 
+static void *linux_gnttab_map_grant_ref_notify(xc_gnttab *xch, xc_osdep_handle 
h,
+                                               uint32_t domid, uint32_t ref,
+                                               uint32_t notify_offset,
+                                               evtchn_port_t notify_port)
+{
+    int fd = (int)h;
+    struct ioctl_gntdev_map_grant_ref map;
+       struct ioctl_gntdev_unmap_notify notify;
+    void *addr;
+
+    map.count = 1;
+    map.refs[0].domid = domid;
+    map.refs[0].ref = ref;
+
+    if ( ioctl(fd, IOCTL_GNTDEV_MAP_GRANT_REF, &map) ) {
+        PERROR("xc_gnttab_map_grant_ref: ioctl MAP_GRANT_REF failed");
+        return NULL;
+    }
+
+    addr = mmap(NULL, XC_PAGE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 
map.index);
+    if ( addr == MAP_FAILED )
+    {
+        int saved_errno = errno;
+        struct ioctl_gntdev_unmap_grant_ref unmap_grant;
+
+        PERROR("xc_gnttab_map_grant_ref: mmap failed");
+        unmap_grant.index = map.index;
+        unmap_grant.count = 1;
+        ioctl(fd, IOCTL_GNTDEV_UNMAP_GRANT_REF, &unmap_grant);
+        errno = saved_errno;
+        return NULL;
+    }
+
+    notify.index = map.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_GNTDEV_SET_UNMAP_NOTIFY, &notify)) {
+        PERROR("linux_gnttab_map_grant_ref_notify: ioctl SET_UNMAP_NOTIFY 
failed");
+    }
+
+    return addr;
+}
+
+
 static int linux_gnttab_munmap(xc_gnttab *xcg, xc_osdep_handle h,
                                void *start_address, uint32_t count)
 {
@@ -662,6 +713,7 @@ static struct xc_osdep_ops linux_gnttab_ops = {
         .map_grant_ref = &linux_gnttab_map_grant_ref,
         .map_grant_refs = &linux_gnttab_map_grant_refs,
         .map_domain_grant_refs = &linux_gnttab_map_domain_grant_refs,
+       .map_grant_ref_notify = &linux_gnttab_map_grant_ref_notify,
         .munmap = &linux_gnttab_munmap,
     },
 };
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 1b82ee0..7859571 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -1349,6 +1349,27 @@ void *xc_gnttab_map_domain_grant_refs(xc_gnttab *xcg,
                                       int prot);
 
 /*
+ * Memory maps a grant reference from one domain to a local address range.
+ * Mappings should be unmapped with xc_gnttab_munmap.  Logs errors.
+ * This version always maps writable pages, and will attempt to set up
+ * an unmap notification at the given offset and event channel. When the
+ * page is unmapped, the byte at the given offset will be zeroed and a
+ * wakeup will be sent to the given event channel.
+ *
+ * @parm xcg a handle on an open grant table interface
+ * @parm domid the domain to map memory from
+ * @parm ref the grant reference ID to map
+ * @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
+ */
+void *xc_gnttab_map_grant_ref_notify(xc_gnttab *xcg,
+                                     uint32_t domid,
+                                     uint32_t ref,
+                                     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_gnttab_map_grant_ref or xc_gnttab_map_grant_refs. Never logs.
  */
diff --git a/tools/libxc/xenctrlosdep.h b/tools/libxc/xenctrlosdep.h
index bfe46e0..01969c5 100644
--- a/tools/libxc/xenctrlosdep.h
+++ b/tools/libxc/xenctrlosdep.h
@@ -119,6 +119,11 @@ struct xc_osdep_ops
                                            uint32_t domid,
                                            uint32_t *refs,
                                            int prot);
+            void *(*map_grant_ref_notify)(xc_gnttab *xcg, xc_osdep_handle h,
+                                          uint32_t domid,
+                                          uint32_t ref,
+                                          uint32_t notify_offset,
+                                          evtchn_port_t notify_port);
             int (*munmap)(xc_gnttab *xcg, xc_osdep_handle h,
                           void *start_address,
                           uint32_t count);
-- 
1.7.6


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel