diff --git a/tools/xenlogd/io.c b/tools/xenlogd/io.c
index 778e1dc2c9..c2b259f42e 100644
--- a/tools/xenlogd/io.c
+++ b/tools/xenlogd/io.c
@@ -18,6 +18,8 @@
 #include <syslog.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <dirent.h>
+#include <fcntl.h>
 #include <xenctrl.h>           /* For cpu barriers. */
 #include <xen-tools/common-macros.h>
 
@@ -28,6 +30,15 @@
 #define P9_CMD_ATTACH     104
 #define P9_CMD_ERROR      107
 #define P9_CMD_WALK       110
+#define P9_CMD_OPEN       112
+
+/* P9 protocol open flags. */
+#define P9_OREAD            0   /* read */
+#define P9_OWRITE           1   /* write */
+#define P9_ORDWR            2   /* read and write */
+#define P9_OMODEMASK     0x03
+#define P9_OTRUNC        0x10   /* or'ed in, truncate file first */
+#define P9_OREMOVE       0x40   /* or'ed in, remove file after clunk */
 
 #define P9_MIN_MSIZE      2048
 #define P9_VERSION        "9P2000.u"
@@ -734,6 +745,121 @@ static void p9_walk(device *device, struct p9_header *hdr)
     free(names);
 }
 
+static int open_flags_from_mode(uint8_t mode)
+{
+    int flags;
+
+    switch ( mode & P9_OMODEMASK )
+    {
+    case P9_OREAD:
+        flags = O_RDONLY;
+        break;
+
+    case P9_OWRITE:
+        flags = O_WRONLY;
+        break;
+
+    case P9_ORDWR:
+        flags = O_RDWR;
+        break;
+
+    default:
+        return -1;
+    }
+
+    if ( mode & P9_OTRUNC )
+        flags |= O_TRUNC;
+
+    return flags;
+}
+
+static unsigned int get_iounit(device *device, struct stat *st)
+{
+    return (device->max_size - st->st_blksize) & ~(st->st_blksize - 1);
+}
+
+static void p9_open(device *device, struct p9_header *hdr)
+{
+    uint32_t fid;
+    uint8_t mode;
+    struct p9_fid *fidp;
+    struct stat st;
+    struct p9_qid qid;
+    uint32_t iounit;
+    int flags;
+    int ret;
+
+    ret = fill_data(device, "Ub", &fid, &mode);
+    if ( ret != 2 )
+    {
+        p9_error(device, hdr->tag, EINVAL);
+        return;
+    }
+    if ( mode & ~(P9_OMODEMASK | P9_OTRUNC | P9_OREMOVE) )
+    {
+        p9_error(device, hdr->tag, EINVAL);
+        return;
+    }
+
+    fidp = find_fid(device, fid);
+    if ( !fidp )
+    {
+        p9_error(device, hdr->tag, ENOENT);
+        return;
+    }
+    if ( fidp->opened )
+    {
+        p9_error(device, hdr->tag, EINVAL);
+        return;
+    }
+
+    if ( stat(fidp->path, &st) < 0 )
+    {
+        p9_error(device, hdr->tag, ENOENT);
+        return;
+    }
+
+    fidp->isdir = S_ISDIR(st.st_mode);
+    fidp->mode = mode;
+    if ( fidp->isdir )
+    {
+        if ( mode != P9_OREAD )
+        {
+            p9_error(device, hdr->tag, EINVAL);
+            return;
+        }
+        fidp->data = opendir(fidp->path);
+        if ( !fidp->data )
+        {
+            p9_error(device, hdr->tag, errno);
+            return;
+        }
+        fidp->fd = dirfd(fidp->data);
+    }
+    else
+    {
+        flags = open_flags_from_mode(mode);
+        if ( flags < 0 )
+        {
+            p9_error(device, hdr->tag, EINVAL);
+            return;
+        }
+
+        fidp->fd = open(fidp->path, flags);
+        if ( fidp->fd < 0 )
+        {
+            p9_error(device, hdr->tag, errno);
+            return;
+        }
+    }
+
+    fill_qid(fidp->path, &qid, &st);
+    iounit = get_iounit(device, &st);
+    fidp->opened = true;
+
+    fill_buffer(device, hdr->cmd + 1, hdr->tag, "QU", &qid, &iounit);
+}
+
 void *io_thread(void *arg)
 {
     device *device = arg;
@@ -801,6 +927,10 @@ void *io_thread(void *arg)
                 p9_walk(device, &hdr);
                 break;
 
+            case P9_CMD_OPEN:
+                p9_open(device, &hdr);
+                break;
+
             default:
                 syslog(LOG_DEBUG, "%u.%u sent unhandled command %u\n",
                        device->domid, device->devid, hdr.cmd);
diff --git a/tools/xenlogd/xenlogd.h b/tools/xenlogd/xenlogd.h
index 23f013af9e..6b7b5e2b91 100644
--- a/tools/xenlogd/xenlogd.h
+++ b/tools/xenlogd/xenlogd.h
@@ -22,7 +22,11 @@ struct p9_header {
 struct p9_fid {
     XEN_TAILQ_ENTRY(struct p9_fid) list;
     unsigned int fid;
+    int fd;
+    uint8_t mode;
     bool opened;
+    bool isdir;
+    void *data;    /* File type specific. */
     char path[];
 };
 
