[Qemu-devel] [PATCH QEMU-XEN v8 3/8] xen: Switch to libxengnttab interface for compat shims.

[Ian Campbell <ian.campbell@citrix.com>]

In Xen 4.7 we are refactoring parts libxenctrl into a number of
separate libraries which will provide backward and forward API and ABI
compatiblity.

One such library will be libxengnttab which provides access to grant
tables.

In preparation for this switch the compatibility layer in xen_common.h
(which support building with older versions of Xen) to use what will
be the new library API. This means that the gnttab shim will disappear
for versions of Xen which include libxengnttab.

To simplify things for the <= 4.0.0 support we wrap the int fd in a
malloc(sizeof int) such that the handle is always a pointer. This
leads to less typedef headaches and the need for
XC_HANDLER_INITIAL_VALUE etc for these interfaces.

Note that this patch does not add any support for actually using
libxengnttab, it just adjusts the existing shims.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
v4: Ran checkpatch, fixed all errors
    Allocate correct size for handle (i.e. not size of the ptr)
    Rebase onto "xen_console: correctly cleanup primary console on
    teardown."

v5: Rebase over b4f72e31b924 "hw/net/xen_nic.c: Free 'netdev->txs'
when map 'netdev->rxs' fails" which added a new gnttab_munmap.

v7: s/gnttab_munmap/gnttab_unmap/ to reflect change in the library.
---
 hw/block/xen_disk.c          | 38 ++++++++++++++++++++------------------
 hw/char/xen_console.c        |  4 ++--
 hw/net/xen_nic.c             | 18 +++++++++---------
 hw/xen/xen_backend.c         | 10 +++++-----
 include/hw/xen/xen_backend.h |  2 +-
 include/hw/xen/xen_common.h  | 42 ++++++++++++++++++++++++++++++++----------
 6 files changed, 69 insertions(+), 45 deletions(-)

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index a48e726..326c948 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -171,11 +171,11 @@ static gint int_cmp(gconstpointer a, gconstpointer b, gpointer user_data)
 static void destroy_grant(gpointer pgnt)
 {
     PersistentGrant *grant = pgnt;
-    XenGnttab gnt = grant->blkdev->xendev.gnttabdev;
+    xengnttab_handle *gnt = grant->blkdev->xendev.gnttabdev;
 
-    if (xc_gnttab_munmap(gnt, grant->page, 1) != 0) {
+    if (xengnttab_unmap(gnt, grant->page, 1) != 0) {
         xen_be_printf(&grant->blkdev->xendev, 0,
-                      "xc_gnttab_munmap failed: %s\n",
+                      "xengnttab_unmap failed: %s\n",
                       strerror(errno));
     }
     grant->blkdev->persistent_gnt_count--;
@@ -188,11 +188,11 @@ static void remove_persistent_region(gpointer data, gpointer dev)
 {
     PersistentRegion *region = data;
     struct XenBlkDev *blkdev = dev;
-    XenGnttab gnt = blkdev->xendev.gnttabdev;
+    xengnttab_handle *gnt = blkdev->xendev.gnttabdev;
 
-    if (xc_gnttab_munmap(gnt, region->addr, region->num) != 0) {
+    if (xengnttab_unmap(gnt, region->addr, region->num) != 0) {
         xen_be_printf(&blkdev->xendev, 0,
-                      "xc_gnttab_munmap region %p failed: %s\n",
+                      "xengnttab_unmap region %p failed: %s\n",
                       region->addr, strerror(errno));
     }
     xen_be_printf(&blkdev->xendev, 3,
@@ -327,7 +327,7 @@ err:
 
 static void ioreq_unmap(struct ioreq *ioreq)
 {
-    XenGnttab gnt = ioreq->blkdev->xendev.gnttabdev;
+    xengnttab_handle *gnt = ioreq->blkdev->xendev.gnttabdev;
     int i;
 
     if (ioreq->num_unmap == 0 || ioreq->mapped == 0) {
@@ -337,8 +337,9 @@ static void ioreq_unmap(struct ioreq *ioreq)
         if (!ioreq->pages) {
             return;
         }
-        if (xc_gnttab_munmap(gnt, ioreq->pages, ioreq->num_unmap) != 0) {
-            xen_be_printf(&ioreq->blkdev->xendev, 0, "xc_gnttab_munmap failed: %s\n",
+        if (xengnttab_unmap(gnt, ioreq->pages, ioreq->num_unmap) != 0) {
+            xen_be_printf(&ioreq->blkdev->xendev, 0,
+                          "xengnttab_unmap failed: %s\n",
                           strerror(errno));
         }
         ioreq->blkdev->cnt_map -= ioreq->num_unmap;
@@ -348,8 +349,9 @@ static void ioreq_unmap(struct ioreq *ioreq)
             if (!ioreq->page[i]) {
                 continue;
             }
-            if (xc_gnttab_munmap(gnt, ioreq->page[i], 1) != 0) {
-                xen_be_printf(&ioreq->blkdev->xendev, 0, "xc_gnttab_munmap failed: %s\n",
+            if (xengnttab_unmap(gnt, ioreq->page[i], 1) != 0) {
+                xen_be_printf(&ioreq->blkdev->xendev, 0,
+                              "xengnttab_unmap failed: %s\n",
                               strerror(errno));
             }
             ioreq->blkdev->cnt_map--;
@@ -361,7 +363,7 @@ static void ioreq_unmap(struct ioreq *ioreq)
 
 static int ioreq_map(struct ioreq *ioreq)
 {
-    XenGnttab gnt = ioreq->blkdev->xendev.gnttabdev;
+    xengnttab_handle *gnt = ioreq->blkdev->xendev.gnttabdev;
     uint32_t domids[BLKIF_MAX_SEGMENTS_PER_REQUEST];
     uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST];
     void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST];
@@ -412,7 +414,7 @@ static int ioreq_map(struct ioreq *ioreq)
     }
 
     if (batch_maps && new_maps) {
-        ioreq->pages = xc_gnttab_map_grant_refs
+        ioreq->pages = xengnttab_map_grant_refs
             (gnt, new_maps, domids, refs, ioreq->prot);
         if (ioreq->pages == NULL) {
             xen_be_printf(&ioreq->blkdev->xendev, 0,
@@ -428,7 +430,7 @@ static int ioreq_map(struct ioreq *ioreq)
         ioreq->blkdev->cnt_map += new_maps;
     } else if (new_maps)  {
         for (i = 0; i < new_maps; i++) {
-            ioreq->page[i] = xc_gnttab_map_grant_ref
+            ioreq->page[i] = xengnttab_map_grant_ref
                 (gnt, domids[i], refs[i], ioreq->prot);
             if (ioreq->page[i] == NULL) {
                 xen_be_printf(&ioreq->blkdev->xendev, 0,
@@ -778,9 +780,9 @@ static void blk_alloc(struct XenDevice *xendev)
     if (xen_mode != XEN_EMULATE) {
         batch_maps = 1;
     }
-    if (xc_gnttab_set_max_grants(xendev->gnttabdev,
+    if (xengnttab_set_max_grants(xendev->gnttabdev,
             MAX_GRANTS(max_requests, BLKIF_MAX_SEGMENTS_PER_REQUEST)) < 0) {
-        xen_be_printf(xendev, 0, "xc_gnttab_set_max_grants failed: %s\n",
+        xen_be_printf(xendev, 0, "xengnttab_set_max_grants failed: %s\n",
                       strerror(errno));
     }
 }
@@ -990,7 +992,7 @@ static int blk_connect(struct XenDevice *xendev)
         }
     }
 
-    blkdev->sring = xc_gnttab_map_grant_ref(blkdev->xendev.gnttabdev,
+    blkdev->sring = xengnttab_map_grant_ref(blkdev->xendev.gnttabdev,
                                             blkdev->xendev.dom,
                                             blkdev->ring_ref,
                                             PROT_READ | PROT_WRITE);
@@ -1055,7 +1057,7 @@ static void blk_disconnect(struct XenDevice *xendev)
     xen_be_unbind_evtchn(&blkdev->xendev);
 
     if (blkdev->sring) {
-        xc_gnttab_munmap(blkdev->xendev.gnttabdev, blkdev->sring, 1);
+        xengnttab_unmap(blkdev->xendev.gnttabdev, blkdev->sring, 1);
         blkdev->cnt_map--;
         blkdev->sring = NULL;
     }
diff --git a/hw/char/xen_console.c b/hw/char/xen_console.c
index 63ade33..ac1b324 100644
--- a/hw/char/xen_console.c
+++ b/hw/char/xen_console.c
@@ -233,7 +233,7 @@ static int con_initialise(struct XenDevice *xendev)
                                           PROT_READ|PROT_WRITE,
                                           con->ring_ref);
     } else {
-        con->sring = xc_gnttab_map_grant_ref(xendev->gnttabdev, con->xendev.dom,
+        con->sring = xengnttab_map_grant_ref(xendev->gnttabdev, con->xendev.dom,
                                              con->ring_ref,
                                              PROT_READ|PROT_WRITE);
     }
@@ -275,7 +275,7 @@ static void con_disconnect(struct XenDevice *xendev)
         if (!xendev->dev) {
             munmap(con->sring, XC_PAGE_SIZE);
         } else {
-            xc_gnttab_munmap(xendev->gnttabdev, con->sring, 1);
+            xengnttab_unmap(xendev->gnttabdev, con->sring, 1);
         }
         con->sring = NULL;
     }
diff --git a/hw/net/xen_nic.c b/hw/net/xen_nic.c
index 0da16b4..3ffb07d 100644
--- a/hw/net/xen_nic.c
+++ b/hw/net/xen_nic.c
@@ -168,7 +168,7 @@ static void net_tx_packets(struct XenNetDev *netdev)
                           (txreq.flags & NETTXF_more_data)      ? " more_data"      : "",
                           (txreq.flags & NETTXF_extra_info)     ? " extra_info"     : "");
 
-            page = xc_gnttab_map_grant_ref(netdev->xendev.gnttabdev,
+            page = xengnttab_map_grant_ref(netdev->xendev.gnttabdev,
                                            netdev->xendev.dom,
                                            txreq.gref, PROT_READ);
             if (page == NULL) {
@@ -190,7 +190,7 @@ static void net_tx_packets(struct XenNetDev *netdev)
                 qemu_send_packet(qemu_get_queue(netdev->nic),
                                  page + txreq.offset, txreq.size);
             }
-            xc_gnttab_munmap(netdev->xendev.gnttabdev, page, 1);
+            xengnttab_unmap(netdev->xendev.gnttabdev, page, 1);
             net_tx_response(netdev, &txreq, NETIF_RSP_OKAY);
         }
         if (!netdev->tx_work) {
@@ -260,7 +260,7 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
     memcpy(&rxreq, RING_GET_REQUEST(&netdev->rx_ring, rc), sizeof(rxreq));
     netdev->rx_ring.req_cons = ++rc;
 
-    page = xc_gnttab_map_grant_ref(netdev->xendev.gnttabdev,
+    page = xengnttab_map_grant_ref(netdev->xendev.gnttabdev,
                                    netdev->xendev.dom,
                                    rxreq.gref, PROT_WRITE);
     if (page == NULL) {
@@ -270,7 +270,7 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
         return -1;
     }
     memcpy(page + NET_IP_ALIGN, buf, size);
-    xc_gnttab_munmap(netdev->xendev.gnttabdev, page, 1);
+    xengnttab_unmap(netdev->xendev.gnttabdev, page, 1);
     net_rx_response(netdev, &rxreq, NETIF_RSP_OKAY, NET_IP_ALIGN, size, 0);
 
     return size;
@@ -342,19 +342,19 @@ static int net_connect(struct XenDevice *xendev)
         return -1;
     }
 
-    netdev->txs = xc_gnttab_map_grant_ref(netdev->xendev.gnttabdev,
+    netdev->txs = xengnttab_map_grant_ref(netdev->xendev.gnttabdev,
                                           netdev->xendev.dom,
                                           netdev->tx_ring_ref,
                                           PROT_READ | PROT_WRITE);
     if (!netdev->txs) {
         return -1;
     }
-    netdev->rxs = xc_gnttab_map_grant_ref(netdev->xendev.gnttabdev,
+    netdev->rxs = xengnttab_map_grant_ref(netdev->xendev.gnttabdev,
                                           netdev->xendev.dom,
                                           netdev->rx_ring_ref,
                                           PROT_READ | PROT_WRITE);
     if (!netdev->rxs) {
-        xc_gnttab_munmap(netdev->xendev.gnttabdev, netdev->txs, 1);
+        xengnttab_unmap(netdev->xendev.gnttabdev, netdev->txs, 1);
         netdev->txs = NULL;
         return -1;
     }
@@ -379,11 +379,11 @@ static void net_disconnect(struct XenDevice *xendev)
     xen_be_unbind_evtchn(&netdev->xendev);
 
     if (netdev->txs) {
-        xc_gnttab_munmap(netdev->xendev.gnttabdev, netdev->txs, 1);
+        xengnttab_unmap(netdev->xendev.gnttabdev, netdev->txs, 1);
         netdev->txs = NULL;
     }
     if (netdev->rxs) {
-        xc_gnttab_munmap(netdev->xendev.gnttabdev, netdev->rxs, 1);
+        xengnttab_unmap(netdev->xendev.gnttabdev, netdev->rxs, 1);
         netdev->rxs = NULL;
     }
 }
diff --git a/hw/xen/xen_backend.c b/hw/xen/xen_backend.c
index ae2a1f0..966e34f 100644
--- a/hw/xen/xen_backend.c
+++ b/hw/xen/xen_backend.c
@@ -252,15 +252,15 @@ static struct XenDevice *xen_be_get_xendev(const char *type, int dom, int dev,
     fcntl(xenevtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);
 
     if (ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {
-        xendev->gnttabdev = xen_xc_gnttab_open(NULL, 0);
-        if (xendev->gnttabdev == XC_HANDLER_INITIAL_VALUE) {
+        xendev->gnttabdev = xengnttab_open(NULL, 0);
+        if (xendev->gnttabdev == NULL) {
             xen_be_printf(NULL, 0, "can't open gnttab device\n");
             xenevtchn_close(xendev->evtchndev);
             g_free(xendev);
             return NULL;
         }
     } else {
-        xendev->gnttabdev = XC_HANDLER_INITIAL_VALUE;
+        xendev->gnttabdev = NULL;
     }
 
     QTAILQ_INSERT_TAIL(&xendevs, xendev, next);
@@ -309,8 +309,8 @@ static struct XenDevice *xen_be_del_xendev(int dom, int dev)
         if (xendev->evtchndev != NULL) {
             xenevtchn_close(xendev->evtchndev);
         }
-        if (xendev->gnttabdev != XC_HANDLER_INITIAL_VALUE) {
-            xc_gnttab_close(xendev->gnttabdev);
+        if (xendev->gnttabdev != NULL) {
+            xengnttab_close(xendev->gnttabdev);
         }
 
         QTAILQ_REMOVE(&xendevs, xendev, next);
diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
index a90314f..8e8857b 100644
--- a/include/hw/xen/xen_backend.h
+++ b/include/hw/xen/xen_backend.h
@@ -47,7 +47,7 @@ struct XenDevice {
     int                local_port;
 
     xenevtchn_handle   *evtchndev;
-    XenGnttab          gnttabdev;
+    xengnttab_handle   *gnttabdev;
 
     struct XenDevOps   *ops;
     QTAILQ_ENTRY(XenDevice) next;
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 5c51b44..8f38310 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -40,7 +40,7 @@ static inline void *xc_map_foreign_bulk(int xc_handle, uint32_t dom, int prot,
 
 typedef int XenXC;
 typedef int xenevtchn_handle;
-typedef int XenGnttab;
+typedef int xengnttab_handle;
 
 #  define XC_INTERFACE_FMT "%i"
 #  define XC_HANDLER_INITIAL_VALUE    -1
@@ -72,11 +72,31 @@ static inline int xenevtchn_close(xenevtchn_handle *h)
 #define xenevtchn_unmask(h, p) xc_evtchn_unmask(*h, p)
 #define xenevtchn_unbind(h, p) xc_evtchn_unmask(*h, p)
 
-static inline XenGnttab xen_xc_gnttab_open(void *logger,
-                                           unsigned int open_flags)
+static inline xengnttab_handle *xengnttab_open(void *logger,
+                                               unsigned int open_flags)
 {
-    return xc_gnttab_open();
+    xengnttab_handle *h = malloc(sizeof(*h));
+    if (!h) {
+        return NULL;
+    }
+    *h = xc_gnttab_open();
+    if (*h == -1) {
+        free(h);
+        h = NULL;
+    }
+    return h;
 }
+static inline int xengnttab_close(xengnttab_handle *h)
+{
+    int rc = xc_gnttab_close(*h);
+    free(h);
+    return rc;
+}
+#define xengnttab_set_max_grants(h, n) xc_gnttab_set_max_grants(*h, n)
+#define xengnttab_map_grant_ref(h, d, r, p) xc_gnttab_map_grant_ref(*h, d, r, p)
+#define xengnttab_map_grant_refs(h, c, d, r, p) \
+    xc_gnttab_map_grant_refs(*h, c, d, r, p)
+#define xengnttab_unmap(h, a, n) xc_gnttab_munmap(*h, a, n)
 
 static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
                                           unsigned int open_flags)
@@ -130,7 +150,7 @@ static inline void xs_close(struct xs_handle *xsh)
 
 typedef xc_interface *XenXC;
 typedef xc_evtchn xenevtchn_handle;
-typedef xc_gnttab *XenGnttab;
+typedef xc_gnttab xengnttab_handle;
 
 #  define XC_INTERFACE_FMT "%p"
 #  define XC_HANDLER_INITIAL_VALUE    NULL
@@ -144,11 +164,13 @@ typedef xc_gnttab *XenGnttab;
 #define xenevtchn_unmask(h, p) xc_evtchn_unmask(h, p)
 #define xenevtchn_unbind(h, p) xc_evtchn_unbind(h, p)
 
-static inline XenGnttab xen_xc_gnttab_open(void *logger,
-                                           unsigned int open_flags)
-{
-    return xc_gnttab_open(logger, open_flags);
-}
+#define xengnttab_open(l, f) xc_gnttab_open(l, f)
+#define xengnttab_close(h) xc_gnttab_close(h)
+#define xengnttab_set_max_grants(h, n) xc_gnttab_set_max_grants(h, n)
+#define xengnttab_map_grant_ref(h, d, r, p) xc_gnttab_map_grant_ref(h, d, r, p)
+#define xengnttab_unmap(h, a, n) xc_gnttab_munmap(h, a, n)
+#define xengnttab_map_grant_refs(h, c, d, r, p) \
+    xc_gnttab_map_grant_refs(h, c, d, r, p)
 
 static inline XenXC xen_xc_interface_open(void *logger, void *dombuild_logger,
                                           unsigned int open_flags)
-- 
2.1.4