hw/xen: Implement GNTTABOP_query_size

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

hw/i386/kvm/xen_gnttab.c

@@ -211,3 +211,22 @@ int xen_gnttab_get_version_op(struct gnttab_get_version *get)
     get->version = 1;
     return 0;
 }
+
+int xen_gnttab_query_size_op(struct gnttab_query_size *size)
+{
+    XenGnttabState *s = xen_gnttab_singleton;
+
+    if (!s) {
+        return -ENOTSUP;
+    }
+
+    if (size->dom != DOMID_SELF && size->dom != xen_domid) {
+        size->status = GNTST_bad_domain;
+        return 0;
+    }
+
+    size->status = GNTST_okay;
+    size->nr_frames = s->nr_frames;
+    size->max_nr_frames = s->max_frames;
+    return 0;
+}

hw/i386/kvm/xen_gnttab.h

@@ -17,7 +17,9 @@ int xen_gnttab_map_page(uint64_t idx, uint64_t gfn);
 
 struct gnttab_set_version;
 struct gnttab_get_version;
+struct gnttab_query_size;
 int xen_gnttab_set_version_op(struct gnttab_set_version *set);
 int xen_gnttab_get_version_op(struct gnttab_get_version *get);
+int xen_gnttab_query_size_op(struct gnttab_query_size *size);
 
 #endif /* QEMU_XEN_GNTTAB_H */

target/i386/kvm/xen-emu.c

@@ -1207,7 +1207,21 @@ static bool kvm_xen_hcall_gnttab_op(struct kvm_xen_exit *exit, X86CPU *cpu,
         }
         break;
     }
-    case GNTTABOP_query_size:
+    case GNTTABOP_query_size: {
+        struct gnttab_query_size size;
+
+        qemu_build_assert(sizeof(size) == 16);
+        if (kvm_copy_from_gva(cs, arg, &size, sizeof(size))) {
+            err = -EFAULT;
+            break;
+        }
+
+        err = xen_gnttab_query_size_op(&size);
+        if (!err && kvm_copy_to_gva(cs, arg, &size, sizeof(size))) {
+            err = -EFAULT;
+        }
+        break;
+    }
     case GNTTABOP_setup_table:
     case GNTTABOP_copy:
     case GNTTABOP_map_grant_ref: