[RFC PATCH v7bis 03/19] hw/xen: Add gnttab operations to allow redirection to internal emulation

[David Woodhouse <dwmw2@infradead.org>]

From: David Woodhouse <dwmw@amazon.co.uk>

In emulation, mapping more than one grant ref to be virtually contiguous
would be fairly difficult. The best way to do it might be to make the
ram_block mappings actually backed by a file (shmem or a deleted file,
perhaps) so that we can have multiple *shared* mappings of it. But that
would be fairly intrusive.

Making the backend drivers cope with page *lists* instead of expecting
the mapping to be contiguous is also non-trivial, since some structures
would actually *cross* page boundaries (e.g. the 32-bit blkif responses
which are 12 bytes).

So for now, we'll support only single-page mappings in emulation.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
 hw/xen/xen-bus.c                    | 112 ++------------------
 hw/xen/xen-legacy-backend.c         | 125 ++--------------------
 hw/xen/xen-operations.c             | 157 ++++++++++++++++++++++++++++
 hw/xen/xen_pvdev.c                  |   2 +-
 include/hw/xen/xen-bus.h            |   3 +-
 include/hw/xen/xen-legacy-backend.h |  13 +--
 include/hw/xen/xen_backend_ops.h    |  93 ++++++++++++++++
 include/hw/xen/xen_common.h         |  39 -------
 softmmu/globals.c                   |   1 +
 9 files changed, 273 insertions(+), 272 deletions(-)

diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index d0b1ae93da..b247e86f28 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -947,7 +947,7 @@ static void xen_device_frontend_destroy(XenDevice *xendev)
 void xen_device_set_max_grant_refs(XenDevice *xendev, unsigned int nr_refs,
                                    Error **errp)
 {
-    if (xengnttab_set_max_grants(xendev->xgth, nr_refs)) {
+    if (qemu_xen_gnttab_set_max_grants(xendev->xgth, nr_refs)) {
         error_setg_errno(errp, errno, "xengnttab_set_max_grants failed");
     }
 }
@@ -956,9 +956,8 @@ void *xen_device_map_grant_refs(XenDevice *xendev, uint32_t *refs,
                                 unsigned int nr_refs, int prot,
                                 Error **errp)
 {
-    void *map = xengnttab_map_domain_grant_refs(xendev->xgth, nr_refs,
-                                                xendev->frontend_id, refs,
-                                                prot);
+    void *map = qemu_xen_gnttab_map_refs(xendev->xgth, nr_refs,
+                                         xendev->frontend_id, refs, prot);
 
     if (!map) {
         error_setg_errno(errp, errno,
@@ -971,109 +970,17 @@ void *xen_device_map_grant_refs(XenDevice *xendev, uint32_t *refs,
 void xen_device_unmap_grant_refs(XenDevice *xendev, void *map,
                                  unsigned int nr_refs, Error **errp)
 {
-    if (xengnttab_unmap(xendev->xgth, map, nr_refs)) {
+    if (qemu_xen_gnttab_unmap(xendev->xgth, map, nr_refs)) {
         error_setg_errno(errp, errno, "xengnttab_unmap failed");
     }
 }
 
-static void compat_copy_grant_refs(XenDevice *xendev, bool to_domain,
-                                   XenDeviceGrantCopySegment segs[],
-                                   unsigned int nr_segs, Error **errp)
-{
-    uint32_t *refs = g_new(uint32_t, nr_segs);
-    int prot = to_domain ? PROT_WRITE : PROT_READ;
-    void *map;
-    unsigned int i;
-
-    for (i = 0; i < nr_segs; i++) {
-        XenDeviceGrantCopySegment *seg = &segs[i];
-
-        refs[i] = to_domain ? seg->dest.foreign.ref :
-            seg->source.foreign.ref;
-    }
-
-    map = xengnttab_map_domain_grant_refs(xendev->xgth, nr_segs,
-                                          xendev->frontend_id, refs,
-                                          prot);
-    if (!map) {
-        error_setg_errno(errp, errno,
-                         "xengnttab_map_domain_grant_refs failed");
-        goto done;
-    }
-
-    for (i = 0; i < nr_segs; i++) {
-        XenDeviceGrantCopySegment *seg = &segs[i];
-        void *page = map + (i * XC_PAGE_SIZE);
-
-        if (to_domain) {
-            memcpy(page + seg->dest.foreign.offset, seg->source.virt,
-                   seg->len);
-        } else {
-            memcpy(seg->dest.virt, page + seg->source.foreign.offset,
-                   seg->len);
-        }
-    }
-
-    if (xengnttab_unmap(xendev->xgth, map, nr_segs)) {
-        error_setg_errno(errp, errno, "xengnttab_unmap failed");
-    }
-
-done:
-    g_free(refs);
-}
-
 void xen_device_copy_grant_refs(XenDevice *xendev, bool to_domain,
                                 XenDeviceGrantCopySegment segs[],
                                 unsigned int nr_segs, Error **errp)
 {
-    xengnttab_grant_copy_segment_t *xengnttab_segs;
-    unsigned int i;
-
-    if (!xendev->feature_grant_copy) {
-        compat_copy_grant_refs(xendev, to_domain, segs, nr_segs, errp);
-        return;
-    }
-
-    xengnttab_segs = g_new0(xengnttab_grant_copy_segment_t, nr_segs);
-
-    for (i = 0; i < nr_segs; i++) {
-        XenDeviceGrantCopySegment *seg = &segs[i];
-        xengnttab_grant_copy_segment_t *xengnttab_seg = &xengnttab_segs[i];
-
-        if (to_domain) {
-            xengnttab_seg->flags = GNTCOPY_dest_gref;
-            xengnttab_seg->dest.foreign.domid = xendev->frontend_id;
-            xengnttab_seg->dest.foreign.ref = seg->dest.foreign.ref;
-            xengnttab_seg->dest.foreign.offset = seg->dest.foreign.offset;
-            xengnttab_seg->source.virt = seg->source.virt;
-        } else {
-            xengnttab_seg->flags = GNTCOPY_source_gref;
-            xengnttab_seg->source.foreign.domid = xendev->frontend_id;
-            xengnttab_seg->source.foreign.ref = seg->source.foreign.ref;
-            xengnttab_seg->source.foreign.offset =
-                seg->source.foreign.offset;
-            xengnttab_seg->dest.virt = seg->dest.virt;
-        }
-
-        xengnttab_seg->len = seg->len;
-    }
-
-    if (xengnttab_grant_copy(xendev->xgth, nr_segs, xengnttab_segs)) {
-        error_setg_errno(errp, errno, "xengnttab_grant_copy failed");
-        goto done;
-    }
-
-    for (i = 0; i < nr_segs; i++) {
-        xengnttab_grant_copy_segment_t *xengnttab_seg = &xengnttab_segs[i];
-
-        if (xengnttab_seg->status != GNTST_okay) {
-            error_setg(errp, "xengnttab_grant_copy seg[%u] failed", i);
-            break;
-        }
-    }
-
-done:
-    g_free(xengnttab_segs);
+    qemu_xen_gnttab_grant_copy(xendev->xgth, to_domain, xendev->frontend_id,
+                               (XenGrantCopySegment *)segs, nr_segs, errp);
 }
 
 struct XenEventChannel {
@@ -1235,7 +1142,7 @@ static void xen_device_unrealize(DeviceState *dev)
     xen_device_backend_destroy(xendev);
 
     if (xendev->xgth) {
-        xengnttab_close(xendev->xgth);
+        qemu_xen_gnttab_close(xendev->xgth);
         xendev->xgth = NULL;
     }
 
@@ -1298,15 +1205,12 @@ static void xen_device_realize(DeviceState *dev, Error **errp)
 
     xendev->watch_list = watch_list_create(xendev->xsh);
 
-    xendev->xgth = xengnttab_open(NULL, 0);
+    xendev->xgth = qemu_xen_gnttab_open();
     if (!xendev->xgth) {
         error_setg_errno(errp, errno, "failed xengnttab_open");
         goto unrealize;
     }
 
-    xendev->feature_grant_copy =
-        (xengnttab_grant_copy(xendev->xgth, 0, NULL) == 0);
-
     xen_device_backend_create(xendev, errp);
     if (*errp) {
         goto unrealize;
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 23e8a6fbd8..88d2ae3f0a 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -43,7 +43,6 @@ struct xs_handle *xenstore;
 const char *xen_protocol;
 
 /* private */
-static bool xen_feature_grant_copy;
 static int debug;
 
 int xenstore_write_be_str(struct XenLegacyDevice *xendev, const char *node,
@@ -113,7 +112,7 @@ void xen_be_set_max_grant_refs(struct XenLegacyDevice *xendev,
 {
     assert(xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV);
 
-    if (xengnttab_set_max_grants(xendev->gnttabdev, nr_refs)) {
+    if (qemu_xen_gnttab_set_max_grants(xendev->gnttabdev, nr_refs)) {
         xen_pv_printf(xendev, 0, "xengnttab_set_max_grants failed: %s\n",
                       strerror(errno));
     }
@@ -126,8 +125,8 @@ void *xen_be_map_grant_refs(struct XenLegacyDevice *xendev, uint32_t *refs,
 
     assert(xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV);
 
-    ptr = xengnttab_map_domain_grant_refs(xendev->gnttabdev, nr_refs,
-                                          xen_domid, refs, prot);
+    ptr = qemu_xen_gnttab_map_refs(xendev->gnttabdev, nr_refs, xen_domid, refs,
+                                   prot);
     if (!ptr) {
         xen_pv_printf(xendev, 0,
                       "xengnttab_map_domain_grant_refs failed: %s\n",
@@ -142,119 +141,27 @@ void xen_be_unmap_grant_refs(struct XenLegacyDevice *xendev, void *ptr,
 {
     assert(xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV);
 
-    if (xengnttab_unmap(xendev->gnttabdev, ptr, nr_refs)) {
+    if (qemu_xen_gnttab_unmap(xendev->gnttabdev, ptr, nr_refs)) {
         xen_pv_printf(xendev, 0, "xengnttab_unmap failed: %s\n",
                       strerror(errno));
     }
 }
 
-static int compat_copy_grant_refs(struct XenLegacyDevice *xendev,
-                                  bool to_domain,
-                                  XenGrantCopySegment segs[],
-                                  unsigned int nr_segs)
-{
-    uint32_t *refs = g_new(uint32_t, nr_segs);
-    int prot = to_domain ? PROT_WRITE : PROT_READ;
-    void *pages;
-    unsigned int i;
-
-    for (i = 0; i < nr_segs; i++) {
-        XenGrantCopySegment *seg = &segs[i];
-
-        refs[i] = to_domain ?
-            seg->dest.foreign.ref : seg->source.foreign.ref;
-    }
-
-    pages = xengnttab_map_domain_grant_refs(xendev->gnttabdev, nr_segs,
-                                            xen_domid, refs, prot);
-    if (!pages) {
-        xen_pv_printf(xendev, 0,
-                      "xengnttab_map_domain_grant_refs failed: %s\n",
-                      strerror(errno));
-        g_free(refs);
-        return -1;
-    }
-
-    for (i = 0; i < nr_segs; i++) {
-        XenGrantCopySegment *seg = &segs[i];
-        void *page = pages + (i * XC_PAGE_SIZE);
-
-        if (to_domain) {
-            memcpy(page + seg->dest.foreign.offset, seg->source.virt,
-                   seg->len);
-        } else {
-            memcpy(seg->dest.virt, page + seg->source.foreign.offset,
-                   seg->len);
-        }
-    }
-
-    if (xengnttab_unmap(xendev->gnttabdev, pages, nr_segs)) {
-        xen_pv_printf(xendev, 0, "xengnttab_unmap failed: %s\n",
-                      strerror(errno));
-    }
-
-    g_free(refs);
-    return 0;
-}
-
 int xen_be_copy_grant_refs(struct XenLegacyDevice *xendev,
                            bool to_domain,
                            XenGrantCopySegment segs[],
                            unsigned int nr_segs)
 {
-    xengnttab_grant_copy_segment_t *xengnttab_segs;
-    unsigned int i;
     int rc;
 
     assert(xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV);
 
-    if (!xen_feature_grant_copy) {
-        return compat_copy_grant_refs(xendev, to_domain, segs, nr_segs);
-    }
-
-    xengnttab_segs = g_new0(xengnttab_grant_copy_segment_t, nr_segs);
-
-    for (i = 0; i < nr_segs; i++) {
-        XenGrantCopySegment *seg = &segs[i];
-        xengnttab_grant_copy_segment_t *xengnttab_seg = &xengnttab_segs[i];
-
-        if (to_domain) {
-            xengnttab_seg->flags = GNTCOPY_dest_gref;
-            xengnttab_seg->dest.foreign.domid = xen_domid;
-            xengnttab_seg->dest.foreign.ref = seg->dest.foreign.ref;
-            xengnttab_seg->dest.foreign.offset = seg->dest.foreign.offset;
-            xengnttab_seg->source.virt = seg->source.virt;
-        } else {
-            xengnttab_seg->flags = GNTCOPY_source_gref;
-            xengnttab_seg->source.foreign.domid = xen_domid;
-            xengnttab_seg->source.foreign.ref = seg->source.foreign.ref;
-            xengnttab_seg->source.foreign.offset =
-                seg->source.foreign.offset;
-            xengnttab_seg->dest.virt = seg->dest.virt;
-        }
-
-        xengnttab_seg->len = seg->len;
-    }
-
-    rc = xengnttab_grant_copy(xendev->gnttabdev, nr_segs, xengnttab_segs);
-
+    rc = qemu_xen_gnttab_grant_copy(xendev->gnttabdev, to_domain, xen_domid,
+                                    segs, nr_segs, NULL);
     if (rc) {
-        xen_pv_printf(xendev, 0, "xengnttab_copy failed: %s\n",
-                      strerror(errno));
-    }
-
-    for (i = 0; i < nr_segs; i++) {
-        xengnttab_grant_copy_segment_t *xengnttab_seg =
-            &xengnttab_segs[i];
-
-        if (xengnttab_seg->status != GNTST_okay) {
-            xen_pv_printf(xendev, 0, "segment[%u] status: %d\n", i,
-                          xengnttab_seg->status);
-            rc = -1;
-        }
+        xen_pv_printf(xendev, 0, "xengnttab_grant_copy failed: %s\n",
+                      strerror(-rc));
     }
-
-    g_free(xengnttab_segs);
     return rc;
 }
 
@@ -466,7 +373,7 @@ static int xen_be_try_initialise(struct XenLegacyDevice *xendev)
     }
 
     if (xendev->ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {
-        xendev->gnttabdev = xengnttab_open(NULL, 0);
+        xendev->gnttabdev = qemu_xen_gnttab_open();
         if (xendev->gnttabdev == NULL) {
             xen_pv_printf(NULL, 0, "can't open gnttab device\n");
             return -1;
@@ -524,7 +431,7 @@ static void xen_be_disconnect(struct XenLegacyDevice *xendev,
         xendev->ops->disconnect(xendev);
     }
     if (xendev->gnttabdev) {
-        xengnttab_close(xendev->gnttabdev);
+        qemu_xen_gnttab_close(xendev->gnttabdev);
         xendev->gnttabdev = NULL;
     }
     if (xendev->be_state != state) {
@@ -678,8 +585,6 @@ void xenstore_update_fe(char *watch, struct XenLegacyDevice *xendev)
 
 int xen_be_init(void)
 {
-    xengnttab_handle *gnttabdev;
-
     xenstore = xs_daemon_open();
     if (!xenstore) {
         xen_pv_printf(NULL, 0, "can't connect to xenstored\n");
@@ -688,19 +593,11 @@ int xen_be_init(void)
 
     qemu_set_fd_handler(xs_fileno(xenstore), xenstore_update, NULL, NULL);
 
-    if (xen_xc == NULL || xen_fmem == NULL) {
+    if (xen_evtchn_ops == NULL || xen_gnttab_ops == NULL) {
         /* Check if xen_init() have been called */
         goto err;
     }
 
-    gnttabdev = xengnttab_open(NULL, 0);
-    if (gnttabdev != NULL) {
-        if (xengnttab_grant_copy(gnttabdev, 0, NULL) == 0) {
-            xen_feature_grant_copy = true;
-        }
-        xengnttab_close(gnttabdev);
-    }
-
     xen_sysdev = qdev_new(TYPE_XENSYSDEV);
     sysbus_realize_and_unref(SYS_BUS_DEVICE(xen_sysdev), &error_fatal);
     xen_sysbus = qbus_new(TYPE_XENSYSBUS, xen_sysdev, "xen-sysbus");
diff --git a/hw/xen/xen-operations.c b/hw/xen/xen-operations.c
index 1a959d89e8..eb5fb0a59f 100644
--- a/hw/xen/xen-operations.c
+++ b/hw/xen/xen-operations.c
@@ -21,6 +21,7 @@
  * must be undefined before including xenctrl.h
  */
 #undef XC_WANT_COMPAT_EVTCHN_API
+#undef XC_WANT_COMPAT_GNTTAB_API
 
 #include <xenctrl.h>
 
@@ -43,12 +44,141 @@ typedef evtchn_port_or_error_t xenevtchn_port_or_error_t;
 #define xenevtchn_unmask(h, p) xc_evtchn_unmask(h, p)
 #define xenevtchn_unbind(h, p) xc_evtchn_unbind(h, p)
 
+typedef xc_gnttab xengnttab_handle;
+
+#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)
+#define xengnttab_map_domain_grant_refs(h, c, d, r, p) \
+    xc_gnttab_map_domain_grant_refs(h, c, d, r, p)
+
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
 
 #include <xenevtchn.h>
+#include <xengnttab.h>
 
 #endif
 
+/* Xen before 4.8 */
+
+static int libxengnttab_fallback_grant_copy(xengnttab_handle *xgt,
+                                            bool to_domain, uint32_t domid,
+                                            XenGrantCopySegment segs[],
+                                            unsigned int nr_segs, Error **errp)
+{
+    uint32_t *refs = g_new(uint32_t, nr_segs);
+    int prot = to_domain ? PROT_WRITE : PROT_READ;
+    void *map;
+    unsigned int i;
+    int rc = 0;
+
+    for (i = 0; i < nr_segs; i++) {
+        XenGrantCopySegment *seg = &segs[i];
+
+        refs[i] = to_domain ? seg->dest.foreign.ref :
+            seg->source.foreign.ref;
+    }
+    map = xengnttab_map_domain_grant_refs(xgt, nr_segs, domid, refs, prot);
+    if (!map) {
+        if (errp) {
+            error_setg_errno(errp, errno,
+                             "xengnttab_map_domain_grant_refs failed");
+        }
+        rc = -errno;
+        goto done;
+    }
+
+    for (i = 0; i < nr_segs; i++) {
+        XenGrantCopySegment *seg = &segs[i];
+        void *page = map + (i * XEN_PAGE_SIZE);
+
+        if (to_domain) {
+            memcpy(page + seg->dest.foreign.offset, seg->source.virt,
+                   seg->len);
+        } else {
+            memcpy(seg->dest.virt, page + seg->source.foreign.offset,
+                   seg->len);
+        }
+    }
+
+    if (xengnttab_unmap(xgt, map, nr_segs)) {
+        if (errp) {
+            error_setg_errno(errp, errno, "xengnttab_unmap failed");
+        }
+        rc = -errno;
+    }
+
+done:
+    g_free(refs);
+    return rc;
+}
+
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40800
+
+static int libxengnttab_backend_grant_copy(xengnttab_handle *xgt,
+                                           bool to_domain, uint32_t domid,
+                                           XenGrantCopySegment *segs,
+                                           uint32_t nr_segs, Error **errp)
+{
+    xengnttab_grant_copy_segment_t *xengnttab_segs;
+    unsigned int i;
+    int rc;
+
+    xengnttab_segs = g_new0(xengnttab_grant_copy_segment_t, nr_segs);
+
+    for (i = 0; i < nr_segs; i++) {
+        XenGrantCopySegment *seg = &segs[i];
+        xengnttab_grant_copy_segment_t *xengnttab_seg = &xengnttab_segs[i];
+
+        if (to_domain) {
+            xengnttab_seg->flags = GNTCOPY_dest_gref;
+            xengnttab_seg->dest.foreign.domid = domid;
+            xengnttab_seg->dest.foreign.ref = seg->dest.foreign.ref;
+            xengnttab_seg->dest.foreign.offset = seg->dest.foreign.offset;
+            xengnttab_seg->source.virt = seg->source.virt;
+        } else {
+            xengnttab_seg->flags = GNTCOPY_source_gref;
+            xengnttab_seg->source.foreign.domid = domid;
+            xengnttab_seg->source.foreign.ref = seg->source.foreign.ref;
+            xengnttab_seg->source.foreign.offset =
+                seg->source.foreign.offset;
+            xengnttab_seg->dest.virt = seg->dest.virt;
+        }
+
+        xengnttab_seg->len = seg->len;
+    }
+
+    if (xengnttab_grant_copy(xgt, nr_segs, xengnttab_segs)) {
+        if (errp) {
+            error_setg_errno(errp, errno, "xengnttab_grant_copy failed");
+        }
+        rc = -errno;
+        goto done;
+    }
+
+    rc = 0;
+    for (i = 0; i < nr_segs; i++) {
+        xengnttab_grant_copy_segment_t *xengnttab_seg = &xengnttab_segs[i];
+
+        if (xengnttab_seg->status != GNTST_okay) {
+            if (errp) {
+                error_setg(errp, "xengnttab_grant_copy seg[%u] failed", i);
+            }
+            rc = -EIO;
+            break;
+        }
+    }
+
+done:
+    g_free(xengnttab_segs);
+    return rc;
+}
+#endif
+
 static xenevtchn_handle *libxenevtchn_backend_open(void)
 {
     return xenevtchn_open(NULL, 0);
@@ -65,7 +195,34 @@ struct evtchn_backend_ops libxenevtchn_backend_ops = {
     .pending = xenevtchn_pending,
 };
 
+static xengnttab_handle *libxengnttab_backend_open(void)
+{
+    return xengnttab_open(NULL, 0);
+}
+
+
+static struct gnttab_backend_ops libxengnttab_backend_ops = {
+    .features = XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE,
+    .open = libxengnttab_backend_open,
+    .close = xengnttab_close,
+    .grant_copy = libxengnttab_fallback_grant_copy,
+    .set_max_grants = xengnttab_set_max_grants,
+    .map_refs = xengnttab_map_domain_grant_refs,
+    .unmap = xengnttab_unmap,
+};
+
 void setup_xen_backend_ops(void)
 {
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40800
+    xengnttab_handle *xgt = xengnttab_open(NULL, 0);
+
+    if (xgt) {
+        if (xengnttab_grant_copy(xgt, 0, NULL) == 0) {
+            xen_gnttab_ops->grant_copy = libxengnttab_backend_grant_copy;
+        }
+        xengnttab_close(xgt);
+    }
+#endif
     xen_evtchn_ops = &libxenevtchn_backend_ops;
+    xen_gnttab_ops = &libxengnttab_backend_ops;
 }
diff --git a/hw/xen/xen_pvdev.c b/hw/xen/xen_pvdev.c
index 86a2c8e567..d8582cc74c 100644
--- a/hw/xen/xen_pvdev.c
+++ b/hw/xen/xen_pvdev.c
@@ -309,7 +309,7 @@ void xen_pv_del_xendev(struct XenLegacyDevice *xendev)
         qemu_xen_evtchn_close(xendev->evtchndev);
     }
     if (xendev->gnttabdev != NULL) {
-        xengnttab_close(xendev->gnttabdev);
+        qemu_xen_gnttab_close(xendev->gnttabdev);
     }
 
     QTAILQ_REMOVE(&xendevs, xendev, next);
diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h
index e21b83796e..72d71d1eb7 100644
--- a/include/hw/xen/xen-bus.h
+++ b/include/hw/xen/xen-bus.h
@@ -9,7 +9,7 @@
 #define HW_XEN_BUS_H
 
 #include "hw/xen/xen_backend_ops.h"
-#include "hw/xen/xen_common.h"
+#include "hw/xen/interface/io/xenbus.h"
 #include "hw/sysbus.h"
 #include "qemu/notify.h"
 #include "qom/object.h"
@@ -33,7 +33,6 @@ struct XenDevice {
     bool backend_online;
     XenWatch *backend_online_watch;
     xengnttab_handle *xgth;
-    bool feature_grant_copy;
     bool inactive;
     QLIST_HEAD(, XenEventChannel) event_channels;
     QLIST_ENTRY(XenDevice) list;
diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index 0ef9b772ac..01c12952b7 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -1,8 +1,8 @@
 #ifndef HW_XEN_LEGACY_BACKEND_H
 #define HW_XEN_LEGACY_BACKEND_H
 
-#include "hw/xen/xen_common.h"
 #include "hw/xen/xen_backend_ops.h"
+#include "hw/xen/interface/io/xenbus.h"
 #include "hw/xen/xen_pvdev.h"
 #include "net/net.h"
 #include "qom/object.h"
@@ -55,17 +55,6 @@ void *xen_be_map_grant_refs(struct XenLegacyDevice *xendev, uint32_t *refs,
 void xen_be_unmap_grant_refs(struct XenLegacyDevice *xendev, void *ptr,
                              unsigned int nr_refs);
 
-typedef struct XenGrantCopySegment {
-    union {
-        void *virt;
-        struct {
-            uint32_t ref;
-            off_t offset;
-        } foreign;
-    } source, dest;
-    size_t len;
-} XenGrantCopySegment;
-
 int xen_be_copy_grant_refs(struct XenLegacyDevice *xendev,
                            bool to_domain, XenGrantCopySegment segs[],
                            unsigned int nr_segs);
diff --git a/include/hw/xen/xen_backend_ops.h b/include/hw/xen/xen_backend_ops.h
index 9605456e81..acb7838e63 100644
--- a/include/hw/xen/xen_backend_ops.h
+++ b/include/hw/xen/xen_backend_ops.h
@@ -29,6 +29,12 @@
 typedef struct xenevtchn_handle xenevtchn_handle;
 typedef int xenevtchn_port_or_error_t;
 typedef uint32_t evtchn_port_t;
+typedef uint16_t domid_t;
+typedef uint32_t grant_ref_t;
+
+#define XEN_PAGE_SHIFT       12
+#define XEN_PAGE_SIZE        (1UL << XEN_PAGE_SHIFT)
+#define XEN_PAGE_MASK        (~(XEN_PAGE_SIZE-1))
 
 struct evtchn_backend_ops {
     xenevtchn_handle *(*open)(void);
@@ -113,6 +119,93 @@ static inline int qemu_xen_evtchn_pending(xenevtchn_handle *xc)
     return xen_evtchn_ops->pending(xc);
 }
 
+typedef struct xengntdev_handle xengnttab_handle;
+
+typedef struct XenGrantCopySegment {
+    union {
+        void *virt;
+        struct {
+            uint32_t ref;
+            off_t offset;
+        } foreign;
+    } source, dest;
+    size_t len;
+} XenGrantCopySegment;
+
+#define XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE  (1U << 0)
+
+struct gnttab_backend_ops {
+    uint32_t features;
+    xengnttab_handle *(*open)(void);
+    int (*close)(xengnttab_handle *xgt);
+    int (*grant_copy)(xengnttab_handle *xgt, bool to_domain, uint32_t domid,
+                      XenGrantCopySegment *segs, uint32_t nr_segs,
+                      Error **errp);
+    int (*set_max_grants)(xengnttab_handle *xgt, uint32_t nr_grants);
+    void *(*map_refs)(xengnttab_handle *xgt, uint32_t count, uint32_t domid,
+                      uint32_t *refs, int prot);
+    int (*unmap)(xengnttab_handle *xgt, void *start_address, uint32_t count);
+};
+
+extern struct gnttab_backend_ops *xen_gnttab_ops;
+
+static inline xengnttab_handle *qemu_xen_gnttab_open(void)
+{
+    if (!xen_gnttab_ops) {
+        return NULL;
+    }
+    return xen_gnttab_ops->open();
+}
+
+static inline int qemu_xen_gnttab_close(xengnttab_handle *xgt)
+{
+    if (!xen_gnttab_ops) {
+        return -ENOSYS;
+    }
+    return xen_gnttab_ops->close(xgt);
+}
+
+static inline int qemu_xen_gnttab_grant_copy(xengnttab_handle *xgt,
+                                             bool to_domain, uint32_t domid,
+                                             XenGrantCopySegment *segs,
+                                             uint32_t nr_segs, Error **errp)
+{
+    if (!xen_gnttab_ops) {
+        return -ENOSYS;
+    }
+
+    return xen_gnttab_ops->grant_copy(xgt, to_domain, domid, segs, nr_segs,
+                                      errp);
+}
+
+static inline int qemu_xen_gnttab_set_max_grants(xengnttab_handle *xgt, uint32_t nr_grants)
+{
+    if (!xen_gnttab_ops) {
+        return -ENOSYS;
+    }
+    return xen_gnttab_ops->set_max_grants(xgt, nr_grants);
+}
+
+static inline void *qemu_xen_gnttab_map_refs(xengnttab_handle *xgt, uint32_t count,
+                                             uint32_t domid, uint32_t *refs,
+                                             int prot)
+{
+    if (!xen_gnttab_ops) {
+        return NULL;
+    }
+    return xen_gnttab_ops->map_refs(xgt, count, domid, refs, prot);
+}
+
+static inline int qemu_xen_gnttab_unmap(xengnttab_handle *xgt,
+                                        void *start_address,
+                                        uint32_t count)
+{
+    if (!xen_gnttab_ops) {
+        return -ENOSYS;
+    }
+    return xen_gnttab_ops->unmap(xgt, start_address, count);
+}
+
 void setup_xen_backend_ops(void);
 
 #endif /* QEMU_XEN_BACKEND_OPS_H */
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 34abd0a772..d4d10d3ff1 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -28,17 +28,6 @@ extern xc_interface *xen_xc;
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
 
 typedef xc_interface xenforeignmemory_handle;
-typedef xc_gnttab xengnttab_handle;
-
-#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)
-#define xengnttab_map_domain_grant_refs(h, c, d, r, p) \
-    xc_gnttab_map_domain_grant_refs(h, c, d, r, p)
 
 #define xenforeignmemory_open(l, f) xen_xc
 #define xenforeignmemory_close(h)
@@ -58,7 +47,6 @@ static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
 
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
 
-#include <xengnttab.h>
 #include <xenforeignmemory.h>
 
 #endif
@@ -648,31 +636,4 @@ static inline int xen_set_ioreq_server_state(domid_t dom,
 
 #endif
 
-/* Xen before 4.8 */
-
-#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40800
-
-struct xengnttab_grant_copy_segment {
-    union xengnttab_copy_ptr {
-        void *virt;
-        struct {
-            uint32_t ref;
-            uint16_t offset;
-            uint16_t domid;
-        } foreign;
-    } source, dest;
-    uint16_t len;
-    uint16_t flags;
-    int16_t status;
-};
-
-typedef struct xengnttab_grant_copy_segment xengnttab_grant_copy_segment_t;
-
-static inline int xengnttab_grant_copy(xengnttab_handle *xgt, uint32_t count,
-                                       xengnttab_grant_copy_segment_t *segs)
-{
-    return -ENOSYS;
-}
-#endif
-
 #endif /* QEMU_HW_XEN_COMMON_H */
diff --git a/softmmu/globals.c b/softmmu/globals.c
index eb62739be1..23bb27f0f6 100644
--- a/softmmu/globals.c
+++ b/softmmu/globals.c
@@ -66,3 +66,4 @@ uint32_t xen_domid;
 enum xen_mode xen_mode = XEN_DISABLED;
 bool xen_domid_restrict;
 struct evtchn_backend_ops *xen_evtchn_ops;
+struct gnttab_backend_ops *xen_gnttab_ops;
-- 
2.39.0