Merge branch 'xenfv-kvm-15' of git://git.infradead.org/users/dwmw2/qemu into HEAD

This adds support for emulating Xen under Linux/KVM, based on kernel
patches which have been present since Linux v5.12. As with the kernel
support, it's derived from work started by João Martins of Oracle in
2018.

This series just adds the basic platform support — CPUID, hypercalls,
event channels, a stub of XenStore.

A full single-tenant internal implementation of XenStore, and patches
to make QEMU's Xen PV drivers work with this Xen emulation, are waiting
in the wings to be submitted in a follow-on patch series.

As noted in the documentation, it's enabled by setting the xen-version
property on the KVM accelerator, e.g.:

 qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
    -accel kvm,xen-version=0x4000e,kernel-irqchip=split \
    -kernel vmlinuz-6.0.7-301.fc37.x86_64 \
    -append "console=ttyS0 root=/dev/sda1" \
    -drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
    -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.0

Even before this was merged, we've already been using it to find and fix
bugs in the Linux kernel Xen guest support:

https://lore.kernel.org/all/4bffa69a949bfdc92c4a18e5a1c3cbb3b94a0d32.camel@infradead.org/
https://lore.kernel.org/all/871qnunycr.ffs@tglx/

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 25 insertions, 34 deletions

diff --git a/hw/xen/Kconfig b/hw/xen/Kconfig
new file mode 100644
index 0000000..3467efb
--- /dev/null
+++ b/hw/xen/Kconfig
@@ -0,0 +1,3 @@
+config XEN_BUS
+    bool
+    default y if (XEN || XEN_EMU)
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 085fd31..afba71f 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -676,21 +676,30 @@ void xenstore_update_fe(char *watch, struct XenLegacyDevice *xendev)
 }
 /* -------------------------------------------------------------------- */
 
-int xen_be_init(void)
+static void xen_set_dynamic_sysbus(void)
+{
+    Object *machine = qdev_get_machine();
+    ObjectClass *oc = object_get_class(machine);
+    MachineClass *mc = MACHINE_CLASS(oc);
+
+    machine_class_allow_dynamic_sysbus_dev(mc, TYPE_XENSYSDEV);
+}
+
+void xen_be_init(void)
 {
     xengnttab_handle *gnttabdev;
 
     xenstore = xs_daemon_open();
     if (!xenstore) {
         xen_pv_printf(NULL, 0, "can't connect to xenstored\n");
-        return -1;
+        exit(1);
     }
 
     qemu_set_fd_handler(xs_fileno(xenstore), xenstore_update, NULL, NULL);
 
     if (xen_xc == NULL || xen_fmem == NULL) {
-        /* Check if xen_init() have been called */
-        goto err;
+        xen_pv_printf(NULL, 0, "Xen operations not set up\n");
+        exit(1);
     }
 
     gnttabdev = xengnttab_open(NULL, 0);
@@ -706,23 +715,16 @@ int xen_be_init(void)
     xen_sysbus = qbus_new(TYPE_XENSYSBUS, xen_sysdev, "xen-sysbus");
     qbus_set_bus_hotplug_handler(xen_sysbus);
 
-    return 0;
-
-err:
-    qemu_set_fd_handler(xs_fileno(xenstore), NULL, NULL, NULL);
-    xs_daemon_close(xenstore);
-    xenstore = NULL;
-
-    return -1;
-}
-
-static void xen_set_dynamic_sysbus(void)
-{
-    Object *machine = qdev_get_machine();
-    ObjectClass *oc = object_get_class(machine);
-    MachineClass *mc = MACHINE_CLASS(oc);
+    xen_set_dynamic_sysbus();
 
-    machine_class_allow_dynamic_sysbus_dev(mc, TYPE_XENSYSDEV);
+    xen_be_register("console", &xen_console_ops);
+    xen_be_register("vkbd", &xen_kbdmouse_ops);
+#ifdef CONFIG_VIRTFS
+    xen_be_register("9pfs", &xen_9pfs_ops);
+#endif
+#ifdef CONFIG_USB_LIBUSB
+    xen_be_register("qusb", &xen_usb_ops);
+#endif
 }
 
 int xen_be_register(const char *type, struct XenDevOps *ops)
@@ -744,20 +746,6 @@ int xen_be_register(const char *type, struct XenDevOps *ops)
     return xenstore_scan(type, xen_domid, ops);
 }
 
-void xen_be_register_common(void)
-{
-    xen_set_dynamic_sysbus();
-
-    xen_be_register("console", &xen_console_ops);
-    xen_be_register("vkbd", &xen_kbdmouse_ops);
-#ifdef CONFIG_VIRTFS
-    xen_be_register("9pfs", &xen_9pfs_ops);
-#endif
-#ifdef CONFIG_USB_LIBUSB
-    xen_be_register("qusb", &xen_usb_ops);
-#endif
-}
-
 int xen_be_bind_evtchn(struct XenLegacyDevice *xendev)
 {
     if (xendev->local_port != -1) {