i386/xen: Implement HYPERVISOR_grant_table_op and GNTTABOP_[gs]et_verson

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

hw/i386/kvm/xen_gnttab.c

@@ -180,3 +180,34 @@ int xen_gnttab_map_page(uint64_t idx, uint64_t gfn)
     return 0;
 }
 
+int xen_gnttab_set_version_op(struct gnttab_set_version *set)
+{
+    int ret;
+
+    switch (set->version) {
+    case 1:
+        ret = 0;
+        break;
+
+    case 2:
+        /* Behave as before set_version was introduced. */
+        ret = -ENOSYS;
+        break;
+
+    default:
+        ret = -EINVAL;
+    }
+
+    set->version = 1;
+    return ret;
+}
+
+int xen_gnttab_get_version_op(struct gnttab_get_version *get)
+{
+    if (get->dom != DOMID_SELF && get->dom != xen_domid) {
+        return -ESRCH;
+    }
+
+    get->version = 1;
+    return 0;
+}

hw/i386/kvm/xen_gnttab.h

@@ -15,4 +15,9 @@
 void xen_gnttab_create(void);
 int xen_gnttab_map_page(uint64_t idx, uint64_t gfn);
 
+struct gnttab_set_version;
+struct gnttab_get_version;
+int xen_gnttab_set_version_op(struct gnttab_set_version *set);
+int xen_gnttab_get_version_op(struct gnttab_get_version *get);
+
 #endif /* QEMU_XEN_GNTTAB_H */

target/i386/kvm/xen-emu.c

@@ -34,6 +34,7 @@
 #include "hw/xen/interface/hvm/params.h"
 #include "hw/xen/interface/vcpu.h"
 #include "hw/xen/interface/event_channel.h"
+#include "hw/xen/interface/grant_table.h"
 
 #include "xen-compat.h"
 
@@ -1169,6 +1170,61 @@ static bool kvm_xen_hcall_sched_op(struct kvm_xen_exit *exit, X86CPU *cpu,
     return true;
 }
 
+static bool kvm_xen_hcall_gnttab_op(struct kvm_xen_exit *exit, X86CPU *cpu,
+                                    int cmd, uint64_t arg, int count)
+{
+    CPUState *cs = CPU(cpu);
+    int err;
+
+    switch (cmd) {
+    case GNTTABOP_set_version: {
+        struct gnttab_set_version set;
+
+        qemu_build_assert(sizeof(set) == 4);
+        if (kvm_copy_from_gva(cs, arg, &set, sizeof(set))) {
+            err = -EFAULT;
+            break;
+        }
+
+        err = xen_gnttab_set_version_op(&set);
+        if (!err && kvm_copy_to_gva(cs, arg, &set, sizeof(set))) {
+            err = -EFAULT;
+        }
+        break;
+    }
+    case GNTTABOP_get_version: {
+        struct gnttab_get_version get;
+
+        qemu_build_assert(sizeof(get) == 8);
+        if (kvm_copy_from_gva(cs, arg, &get, sizeof(get))) {
+            err = -EFAULT;
+            break;
+        }
+
+        err = xen_gnttab_get_version_op(&get);
+        if (!err && kvm_copy_to_gva(cs, arg, &get, sizeof(get))) {
+            err = -EFAULT;
+        }
+        break;
+    }
+    case GNTTABOP_query_size:
+    case GNTTABOP_setup_table:
+    case GNTTABOP_copy:
+    case GNTTABOP_map_grant_ref:
+    case GNTTABOP_unmap_grant_ref:
+    case GNTTABOP_swap_grant_ref:
+        return false;
+
+    default:
+        /* Xen explicitly returns -ENOSYS to HVM guests for all others */
+        err = -ENOSYS;
+        break;
+    }
+
+    exit->u.hcall.result = err;
+    return true;
+}
+
 static bool do_kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit)
 {
     uint16_t code = exit->u.hcall.input;
@@ -1179,6 +1235,10 @@ static bool do_kvm_xen_handle_exit(X86CPU *cpu, struct kvm_xen_exit *exit)
     }
 
     switch (code) {
+    case __HYPERVISOR_grant_table_op:
+        return kvm_xen_hcall_gnttab_op(exit, cpu, exit->u.hcall.params[0],
+                                       exit->u.hcall.params[1],
+                                       exit->u.hcall.params[2]);
     case __HYPERVISOR_sched_op:
         return kvm_xen_hcall_sched_op(exit, cpu, exit->u.hcall.params[0],
                                       exit->u.hcall.params[1]);