[PATCH v2 0/7] hw/xen: Simplify legacy backends handling

[PATCH v2 0/7] hw/xen: Simplify legacy backends handling

[Philippe Mathieu-Daudé]

Respin of Paolo's Xen patches from
https://lore.kernel.org/qemu-devel/20240509170044.190795-1-pbonzini@redhat.com/
rebased on one of my cleanup branches making backend
structures const. Treat xenfb as other backends.

Paolo Bonzini (2):
  hw/xen: initialize legacy backends from xen_bus_init()
  hw/xen: register legacy backends via xen_backend_init

Philippe Mathieu-Daudé (5):
  hw/xen: Remove declarations left over in 'xen-legacy-backend.h'
  hw/xen: Constify XenLegacyDevice::XenDevOps
  hw/xen: Constify xenstore_be::XenDevOps
  hw/xen: Make XenDevOps structures const
  hw/xen: Register framebuffer backend via xen_backend_init()

 include/hw/xen/xen-legacy-backend.h | 15 +--------------
 include/hw/xen/xen_pvdev.h          |  3 +--
 hw/9pfs/xen-9p-backend.c            |  8 +++++++-
 hw/display/xenfb.c                  | 15 +++++++++++++--
 hw/i386/pc.c                        |  1 -
 hw/usb/xen-usb.c                    | 14 ++++----------
 hw/xen/xen-bus.c                    |  4 ++++
 hw/xen/xen-hvm-common.c             |  2 --
 hw/xen/xen-legacy-backend.c         | 24 ++++--------------------
 hw/xenpv/xen_machine_pv.c           |  7 +------
 10 files changed, 35 insertions(+), 58 deletions(-)

-- 
2.41.0

[PATCH v2 1/7] hw/xen: Remove declarations left over in 'xen-legacy-backend.h'

[Philippe Mathieu-Daudé]

'xen_blkdev_ops' was removed in commit 19f87870ba ("xen: remove
the legacy 'xen_disk' backend"), 'xen_netdev_ops' in commit
25967ff69f ("hw/xen: update Xen PV NIC to XenDevice model") and
'xen_console_ops' in commit 9b77374690 ("hw/xen: update Xen
console to XenDevice model"). Remove them.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen-legacy-backend.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index 2cca174778..eb22633caa 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -67,14 +67,11 @@ static inline void xen_be_unmap_grant_ref(struct XenLegacyDevice *xendev,
 }
 
 /* actual backend drivers */
-extern struct XenDevOps xen_console_ops;      /* xen_console.c     */
 extern struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
 extern struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
-extern struct XenDevOps xen_blkdev_ops;       /* xen_disk.c        */
 #ifdef CONFIG_VIRTFS
 extern struct XenDevOps xen_9pfs_ops;       /* xen-9p-backend.c        */
 #endif
-extern struct XenDevOps xen_netdev_ops;       /* xen_nic.c         */
 #ifdef CONFIG_USB_LIBUSB
 extern struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
 #endif
-- 
2.41.0

Re: [PATCH v2 1/7] hw/xen: Remove declarations left over in 'xen-legacy-backend.h'

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> 'xen_blkdev_ops' was removed in commit 19f87870ba ("xen: remove
> the legacy 'xen_disk' backend"), 'xen_netdev_ops' in commit
> 25967ff69f ("hw/xen: update Xen PV NIC to XenDevice model") and
> 'xen_console_ops' in commit 9b77374690 ("hw/xen: update Xen
> console to XenDevice model"). Remove them.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 3 ---
>   1 file changed, 3 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 2/7] hw/xen: Constify XenLegacyDevice::XenDevOps

[Philippe Mathieu-Daudé]

XenDevOps @ops is not updated, mark it const.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen_pvdev.h  | 2 +-
 hw/xen/xen-legacy-backend.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/hw/xen/xen_pvdev.h b/include/hw/xen/xen_pvdev.h
index ddad4b9f36..fd9a33e6ab 100644
--- a/include/hw/xen/xen_pvdev.h
+++ b/include/hw/xen/xen_pvdev.h
@@ -53,7 +53,7 @@ struct XenLegacyDevice {
     xenevtchn_handle   *evtchndev;
     xengnttab_handle   *gnttabdev;
 
-    struct XenDevOps   *ops;
+    const struct XenDevOps *ops;
     QTAILQ_ENTRY(XenLegacyDevice) next;
 };
 
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 124dd5f3d6..35f2b57560 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -170,7 +170,7 @@ int xen_be_copy_grant_refs(struct XenLegacyDevice *xendev,
  */
 static struct XenLegacyDevice *xen_be_get_xendev(const char *type, int dom,
                                                  int dev,
-                                                 struct XenDevOps *ops)
+                                                 const struct XenDevOps *ops)
 {
     struct XenLegacyDevice *xendev;
 
-- 
2.41.0

Re: [PATCH v2 2/7] hw/xen: Constify XenLegacyDevice::XenDevOps

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> XenDevOps @ops is not updated, mark it const.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen_pvdev.h  | 2 +-
>   hw/xen/xen-legacy-backend.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 3/7] hw/xen: Constify xenstore_be::XenDevOps

[Philippe Mathieu-Daudé]

XenDevOps @ops is not updated, mark it const.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen-legacy-backend.h | 2 +-
 hw/xen/xen-legacy-backend.c         | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index eb22633caa..2b2e43c7e7 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -40,7 +40,7 @@ void xen_be_check_state(struct XenLegacyDevice *xendev);
 
 /* xen backend driver bits */
 void xen_be_init(void);
-int xen_be_register(const char *type, struct XenDevOps *ops);
+int xen_be_register(const char *type, const struct XenDevOps *ops);
 int xen_be_set_state(struct XenLegacyDevice *xendev, enum xenbus_state state);
 int xen_be_bind_evtchn(struct XenLegacyDevice *xendev);
 void xen_be_set_max_grant_refs(struct XenLegacyDevice *xendev,
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 35f2b57560..4dc3a561cf 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -520,7 +520,7 @@ void xen_be_check_state(struct XenLegacyDevice *xendev)
 struct xenstore_be {
     const char *type;
     int dom;
-    struct XenDevOps *ops;
+    const struct XenDevOps *ops;
 };
 
 static void xenstore_update_be(void *opaque, const char *watch)
@@ -557,7 +557,7 @@ static void xenstore_update_be(void *opaque, const char *watch)
     }
 }
 
-static int xenstore_scan(const char *type, int dom, struct XenDevOps *ops)
+static int xenstore_scan(const char *type, int dom, const struct XenDevOps *ops)
 {
     struct XenLegacyDevice *xendev;
     char path[XEN_BUFSIZE];
@@ -632,7 +632,7 @@ void xen_be_init(void)
 #endif
 }
 
-int xen_be_register(const char *type, struct XenDevOps *ops)
+int xen_be_register(const char *type, const struct XenDevOps *ops)
 {
     char path[50];
     int rc;
-- 
2.41.0

Re: [PATCH v2 3/7] hw/xen: Constify xenstore_be::XenDevOps

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> XenDevOps @ops is not updated, mark it const.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 2 +-
>   hw/xen/xen-legacy-backend.c         | 6 +++---
>   2 files changed, 4 insertions(+), 4 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 4/7] hw/xen: Make XenDevOps structures const

[Philippe Mathieu-Daudé]

Keep XenDevOps structures in .rodata.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen-legacy-backend.h | 8 ++++----
 hw/9pfs/xen-9p-backend.c            | 2 +-
 hw/display/xenfb.c                  | 4 ++--
 hw/usb/xen-usb.c                    | 4 ++--
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index 2b2e43c7e7..cfa43a984a 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -67,13 +67,13 @@ static inline void xen_be_unmap_grant_ref(struct XenLegacyDevice *xendev,
 }
 
 /* actual backend drivers */
-extern struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
-extern struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
+extern const struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
+extern const struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
 #ifdef CONFIG_VIRTFS
-extern struct XenDevOps xen_9pfs_ops;       /* xen-9p-backend.c        */
+extern const struct XenDevOps xen_9pfs_ops;         /* xen-9p-backend.c  */
 #endif
 #ifdef CONFIG_USB_LIBUSB
-extern struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
+extern const struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
 #endif
 
 /* configuration (aka xenbus setup) */
diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 4aa9c8c736..b1780eb819 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -513,7 +513,7 @@ static void xen_9pfs_alloc(struct XenLegacyDevice *xendev)
     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
 }
 
-struct XenDevOps xen_9pfs_ops = {
+const struct XenDevOps xen_9pfs_ops = {
     .size       = sizeof(Xen9pfsDev),
     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
     .alloc      = xen_9pfs_alloc,
diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index b2130a0d70..dd83d0f5a5 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -972,7 +972,7 @@ static void fb_event(struct XenLegacyDevice *xendev)
 
 /* -------------------------------------------------------------------- */
 
-struct XenDevOps xen_kbdmouse_ops = {
+const struct XenDevOps xen_kbdmouse_ops = {
     .size       = sizeof(struct XenInput),
     .init       = input_init,
     .initialise = input_initialise,
@@ -981,7 +981,7 @@ struct XenDevOps xen_kbdmouse_ops = {
     .event      = input_event,
 };
 
-struct XenDevOps xen_framebuffer_ops = {
+const struct XenDevOps xen_framebuffer_ops = {
     .size       = sizeof(struct XenFB),
     .init       = fb_init,
     .initialise = fb_initialise,
diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
index 09ec326aea..95a901e81f 100644
--- a/hw/usb/xen-usb.c
+++ b/hw/usb/xen-usb.c
@@ -1083,7 +1083,7 @@ static void usbback_event(struct XenLegacyDevice *xendev)
     qemu_bh_schedule(usbif->bh);
 }
 
-struct XenDevOps xen_usb_ops = {
+const struct XenDevOps xen_usb_ops = {
     .size            = sizeof(struct usbback_info),
     .flags           = DEVOPS_FLAG_NEED_GNTDEV,
     .init            = usbback_init,
@@ -1102,7 +1102,7 @@ static int usbback_not_supported(void)
     return -EINVAL;
 }
 
-struct XenDevOps xen_usb_ops = {
+const struct XenDevOps xen_usb_ops = {
     .backend_register = usbback_not_supported,
 };
 
-- 
2.41.0

Re: [PATCH v2 4/7] hw/xen: Make XenDevOps structures const

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> Keep XenDevOps structures in .rodata.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 8 ++++----
>   hw/9pfs/xen-9p-backend.c            | 2 +-
>   hw/display/xenfb.c                  | 4 ++--
>   hw/usb/xen-usb.c                    | 4 ++--
>   4 files changed, 9 insertions(+), 9 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 5/7] hw/xen: initialize legacy backends from xen_bus_init()

[Philippe Mathieu-Daudé]

From: Paolo Bonzini <pbonzini@redhat.com>

Prepare for moving the calls to xen_be_register() under the
control of xen_bus_init(), using the normal xen_backend_init()
method that is used by the "modern" backends.

This requires the xenstore global variable to be initialized,
which is done by xen_be_init().  To ensure that everything is
ready at the time the xen_backend_init() functions are called,
remove the xen_be_init() function from all the boards and
place it directly in xen_bus_init().

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240509170044.190795-7-pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/i386/pc.c              | 1 -
 hw/xen/xen-bus.c          | 4 ++++
 hw/xen/xen-hvm-common.c   | 2 --
 hw/xenpv/xen_machine_pv.c | 5 +----
 4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 505ea750f4..19f21953b4 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1250,7 +1250,6 @@ void pc_basic_device_init(struct PCMachineState *pcms,
             pci_create_simple(pcms->pcibus, -1, "xen-platform");
         }
         xen_bus_init();
-        xen_be_init();
     }
 #endif
 
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index fb82cc33e4..95b207ac8b 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -13,6 +13,7 @@
 #include "hw/sysbus.h"
 #include "hw/xen/xen.h"
 #include "hw/xen/xen-backend.h"
+#include "hw/xen/xen-legacy-backend.h" /* xen_be_init() */
 #include "hw/xen/xen-bus.h"
 #include "hw/xen/xen-bus-helper.h"
 #include "monitor/monitor.h"
@@ -329,6 +330,9 @@ static void xen_bus_realize(BusState *bus, Error **errp)
         goto fail;
     }
 
+    /* Initialize legacy backend core & drivers */
+    xen_be_init();
+
     if (xs_node_scanf(xenbus->xsh, XBT_NULL, "", /* domain root node */
                       "domid", NULL, "%u", &domid) == 1) {
         xenbus->backend_id = domid;
diff --git a/hw/xen/xen-hvm-common.c b/hw/xen/xen-hvm-common.c
index 1627da7398..2d1b032121 100644
--- a/hw/xen/xen-hvm-common.c
+++ b/hw/xen/xen-hvm-common.c
@@ -872,8 +872,6 @@ void xen_register_ioreq(XenIOState *state, unsigned int max_cpus,
 
     xen_bus_init();
 
-    xen_be_init();
-
     return;
 
 err:
diff --git a/hw/xenpv/xen_machine_pv.c b/hw/xenpv/xen_machine_pv.c
index 1130d1a147..b500ce0989 100644
--- a/hw/xenpv/xen_machine_pv.c
+++ b/hw/xenpv/xen_machine_pv.c
@@ -34,8 +34,7 @@ static void xen_init_pv(MachineState *machine)
 {
     setup_xen_backend_ops();
 
-    /* Initialize backend core & drivers */
-    xen_be_init();
+    xen_bus_init();
 
     switch (xen_mode) {
     case XEN_ATTACH:
@@ -60,8 +59,6 @@ static void xen_init_pv(MachineState *machine)
         vga_interface_created = true;
     }
 
-    xen_bus_init();
-
     /* config cleanup hook */
     atexit(xen_config_cleanup);
 }
-- 
2.41.0

Re: [PATCH v2 5/7] hw/xen: initialize legacy backends from xen_bus_init()

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> Prepare for moving the calls to xen_be_register() under the
> control of xen_bus_init(), using the normal xen_backend_init()
> method that is used by the "modern" backends.
> 
> This requires the xenstore global variable to be initialized,
> which is done by xen_be_init().  To ensure that everything is
> ready at the time the xen_backend_init() functions are called,
> remove the xen_be_init() function from all the boards and
> place it directly in xen_bus_init().
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Message-ID: <20240509170044.190795-7-pbonzini@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   hw/i386/pc.c              | 1 -
>   hw/xen/xen-bus.c          | 4 ++++
>   hw/xen/xen-hvm-common.c   | 2 --
>   hw/xenpv/xen_machine_pv.c | 5 +----
>   4 files changed, 5 insertions(+), 7 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 6/7] hw/xen: register legacy backends via xen_backend_init

[Philippe Mathieu-Daudé]

From: Paolo Bonzini <pbonzini@redhat.com>

It is okay to register legacy backends in the middle of xen_bus_init().
All that the registration does is record the existence of the backend
in xenstore.

This makes it possible to remove them from the build without introducing
undefined symbols in xen_be_init().  It also removes the need for the
backend_register callback, whose only purpose is to avoid registering
nonfunctional backends.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240509170044.190795-8-pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen-legacy-backend.h | 11 ++---------
 include/hw/xen/xen_pvdev.h          |  1 -
 hw/9pfs/xen-9p-backend.c            |  8 +++++++-
 hw/display/xenfb.c                  |  8 +++++++-
 hw/usb/xen-usb.c                    | 14 ++++----------
 hw/xen/xen-legacy-backend.c         | 16 ----------------
 6 files changed, 20 insertions(+), 38 deletions(-)

diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index cfa43a984a..e55a14057f 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -66,15 +66,8 @@ static inline void xen_be_unmap_grant_ref(struct XenLegacyDevice *xendev,
     return xen_be_unmap_grant_refs(xendev, ptr, &ref, 1);
 }
 
-/* actual backend drivers */
-extern const struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
-extern const struct XenDevOps xen_framebuffer_ops;  /* xen_framebuffer.c */
-#ifdef CONFIG_VIRTFS
-extern const struct XenDevOps xen_9pfs_ops;         /* xen-9p-backend.c  */
-#endif
-#ifdef CONFIG_USB_LIBUSB
-extern const struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
-#endif
+/* backend drivers not included in all machines */
+extern const struct XenDevOps xen_framebuffer_ops;  /* xenfb.c */
 
 /* configuration (aka xenbus setup) */
 void xen_config_cleanup(void);
diff --git a/include/hw/xen/xen_pvdev.h b/include/hw/xen/xen_pvdev.h
index fd9a33e6ab..0c98444047 100644
--- a/include/hw/xen/xen_pvdev.h
+++ b/include/hw/xen/xen_pvdev.h
@@ -29,7 +29,6 @@ struct XenDevOps {
                                  const char *node);
     void      (*frontend_changed)(struct XenLegacyDevice *xendev,
                                   const char *node);
-    int       (*backend_register)(void);
 };
 
 struct XenLegacyDevice {
diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index b1780eb819..79359d911a 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -513,7 +513,7 @@ static void xen_9pfs_alloc(struct XenLegacyDevice *xendev)
     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
 }
 
-const struct XenDevOps xen_9pfs_ops = {
+static const struct XenDevOps xen_9pfs_ops = {
     .size       = sizeof(Xen9pfsDev),
     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
     .alloc      = xen_9pfs_alloc,
@@ -522,3 +522,9 @@ const struct XenDevOps xen_9pfs_ops = {
     .disconnect = xen_9pfs_disconnect,
     .free       = xen_9pfs_free,
 };
+
+static void xen_9pfs_register_backend(void)
+{
+    xen_be_register("9pfs", &xen_9pfs_ops);
+}
+xen_backend_init(xen_9pfs_register_backend);
diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index dd83d0f5a5..b6d370bdf6 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -972,7 +972,7 @@ static void fb_event(struct XenLegacyDevice *xendev)
 
 /* -------------------------------------------------------------------- */
 
-const struct XenDevOps xen_kbdmouse_ops = {
+static const struct XenDevOps xen_kbdmouse_ops = {
     .size       = sizeof(struct XenInput),
     .init       = input_init,
     .initialise = input_initialise,
@@ -995,3 +995,9 @@ static const GraphicHwOps xenfb_ops = {
     .gfx_update  = xenfb_update,
     .ui_info     = xenfb_ui_info,
 };
+
+static void xen_vkbd_register_backend(void)
+{
+    xen_be_register("vkbd", &xen_kbdmouse_ops);
+}
+xen_backend_init(xen_vkbd_register_backend);
diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
index 95a901e81f..13901625c0 100644
--- a/hw/usb/xen-usb.c
+++ b/hw/usb/xen-usb.c
@@ -1083,7 +1083,7 @@ static void usbback_event(struct XenLegacyDevice *xendev)
     qemu_bh_schedule(usbif->bh);
 }
 
-const struct XenDevOps xen_usb_ops = {
+static const struct XenDevOps xen_usb_ops = {
     .size            = sizeof(struct usbback_info),
     .flags           = DEVOPS_FLAG_NEED_GNTDEV,
     .init            = usbback_init,
@@ -1095,15 +1095,9 @@ const struct XenDevOps xen_usb_ops = {
     .event           = usbback_event,
 };
 
-#else /* USBIF_SHORT_NOT_OK */
-
-static int usbback_not_supported(void)
+static void xen_usb_register_backend(void)
 {
-    return -EINVAL;
+    xen_be_register("qusb", &xen_usb_ops);
 }
-
-const struct XenDevOps xen_usb_ops = {
-    .backend_register = usbback_not_supported,
-};
-
+xen_backend_init(xen_usb_register_backend);
 #endif
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 4dc3a561cf..5514184f9c 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -622,27 +622,11 @@ void xen_be_init(void)
     qbus_set_bus_hotplug_handler(xen_sysbus);
 
     xen_set_dynamic_sysbus();
-
-    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, const struct XenDevOps *ops)
 {
     char path[50];
-    int rc;
-
-    if (ops->backend_register) {
-        rc = ops->backend_register();
-        if (rc) {
-            return rc;
-        }
-    }
 
     snprintf(path, sizeof(path), "device-model/%u/backends/%s", xen_domid,
              type);
-- 
2.41.0

Re: [PATCH v2 6/7] hw/xen: register legacy backends via xen_backend_init

[Philippe Mathieu-Daudé]

On 10/5/24 12:49, Philippe Mathieu-Daudé wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> It is okay to register legacy backends in the middle of xen_bus_init().
> All that the registration does is record the existence of the backend
> in xenstore.
> 
> This makes it possible to remove them from the build without introducing
> undefined symbols in xen_be_init().  It also removes the need for the
> backend_register callback, whose only purpose is to avoid registering
> nonfunctional backends.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Message-ID: <20240509170044.190795-8-pbonzini@redhat.com>

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 11 ++---------
>   include/hw/xen/xen_pvdev.h          |  1 -
>   hw/9pfs/xen-9p-backend.c            |  8 +++++++-
>   hw/display/xenfb.c                  |  8 +++++++-
>   hw/usb/xen-usb.c                    | 14 ++++----------
>   hw/xen/xen-legacy-backend.c         | 16 ----------------
>   6 files changed, 20 insertions(+), 38 deletions(-)

Re: [PATCH v2 6/7] hw/xen: register legacy backends via xen_backend_init

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> It is okay to register legacy backends in the middle of xen_bus_init().
> All that the registration does is record the existence of the backend
> in xenstore.
> 
> This makes it possible to remove them from the build without introducing
> undefined symbols in xen_be_init().  It also removes the need for the
> backend_register callback, whose only purpose is to avoid registering
> nonfunctional backends.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Message-ID: <20240509170044.190795-8-pbonzini@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 11 ++---------
>   include/hw/xen/xen_pvdev.h          |  1 -
>   hw/9pfs/xen-9p-backend.c            |  8 +++++++-
>   hw/display/xenfb.c                  |  8 +++++++-
>   hw/usb/xen-usb.c                    | 14 ++++----------
>   hw/xen/xen-legacy-backend.c         | 16 ----------------
>   6 files changed, 20 insertions(+), 38 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

[PATCH v2 7/7] hw/xen: Register framebuffer backend via xen_backend_init()

[Philippe Mathieu-Daudé]

Align the framebuffer backend with the other legacy ones,
register it via xen_backend_init() when '-vga xenfb' is
used. It is safe because MODULE_INIT_XEN_BACKEND is called
in xen_bus_realize(), long after CLI processing initialized
the vga_interface_type variable.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/xen/xen-legacy-backend.h | 3 ---
 hw/display/xenfb.c                  | 9 +++++++--
 hw/xenpv/xen_machine_pv.c           | 2 --
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index e55a14057f..943732b8d1 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -66,9 +66,6 @@ static inline void xen_be_unmap_grant_ref(struct XenLegacyDevice *xendev,
     return xen_be_unmap_grant_refs(xendev, ptr, &ref, 1);
 }
 
-/* backend drivers not included in all machines */
-extern const struct XenDevOps xen_framebuffer_ops;  /* xenfb.c */
-
 /* configuration (aka xenbus setup) */
 void xen_config_cleanup(void);
 int xen_config_dev_vfb(int vdev, const char *type);
diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index b6d370bdf6..ff442ced1a 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -29,6 +29,7 @@
 
 #include "ui/input.h"
 #include "ui/console.h"
+#include "sysemu/sysemu.h"
 #include "hw/xen/xen-legacy-backend.h"
 
 #include "hw/xen/interface/io/fbif.h"
@@ -996,8 +997,12 @@ static const GraphicHwOps xenfb_ops = {
     .ui_info     = xenfb_ui_info,
 };
 
-static void xen_vkbd_register_backend(void)
+static void xen_ui_register_backend(void)
 {
     xen_be_register("vkbd", &xen_kbdmouse_ops);
+
+    if (vga_interface_type == VGA_XENFB) {
+        xen_be_register("vfb", &xen_framebuffer_ops);
+    }
 }
-xen_backend_init(xen_vkbd_register_backend);
+xen_backend_init(xen_ui_register_backend);
diff --git a/hw/xenpv/xen_machine_pv.c b/hw/xenpv/xen_machine_pv.c
index b500ce0989..24395f42cb 100644
--- a/hw/xenpv/xen_machine_pv.c
+++ b/hw/xenpv/xen_machine_pv.c
@@ -50,8 +50,6 @@ static void xen_init_pv(MachineState *machine)
         break;
     }
 
-    xen_be_register("vfb", &xen_framebuffer_ops);
-
     /* configure framebuffer */
     if (vga_interface_type == VGA_XENFB) {
         xen_config_dev_vfb(0, "vnc");
-- 
2.41.0

Re: [PATCH v2 7/7] hw/xen: Register framebuffer backend via xen_backend_init()

[Paul Durrant]

On 10/05/2024 11:49, Philippe Mathieu-Daudé wrote:
> Align the framebuffer backend with the other legacy ones,
> register it via xen_backend_init() when '-vga xenfb' is
> used. It is safe because MODULE_INIT_XEN_BACKEND is called
> in xen_bus_realize(), long after CLI processing initialized
> the vga_interface_type variable.
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>   include/hw/xen/xen-legacy-backend.h | 3 ---
>   hw/display/xenfb.c                  | 9 +++++++--
>   hw/xenpv/xen_machine_pv.c           | 2 --
>   3 files changed, 7 insertions(+), 7 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>

Re: [PATCH v2 0/7] hw/xen: Simplify legacy backends handling

[Philippe Mathieu-Daudé]

ping?

On 10/5/24 12:49, Philippe Mathieu-Daudé wrote:
> Respin of Paolo's Xen patches from
> https://lore.kernel.org/qemu-devel/20240509170044.190795-1-pbonzini@redhat.com/
> rebased on one of my cleanup branches making backend
> structures const. Treat xenfb as other backends.
> 
> Paolo Bonzini (2):
>    hw/xen: initialize legacy backends from xen_bus_init()
>    hw/xen: register legacy backends via xen_backend_init
> 
> Philippe Mathieu-Daudé (5):
>    hw/xen: Remove declarations left over in 'xen-legacy-backend.h'
>    hw/xen: Constify XenLegacyDevice::XenDevOps
>    hw/xen: Constify xenstore_be::XenDevOps
>    hw/xen: Make XenDevOps structures const
>    hw/xen: Register framebuffer backend via xen_backend_init()
> 
>   include/hw/xen/xen-legacy-backend.h | 15 +--------------
>   include/hw/xen/xen_pvdev.h          |  3 +--
>   hw/9pfs/xen-9p-backend.c            |  8 +++++++-
>   hw/display/xenfb.c                  | 15 +++++++++++++--
>   hw/i386/pc.c                        |  1 -
>   hw/usb/xen-usb.c                    | 14 ++++----------
>   hw/xen/xen-bus.c                    |  4 ++++
>   hw/xen/xen-hvm-common.c             |  2 --
>   hw/xen/xen-legacy-backend.c         | 24 ++++--------------------
>   hw/xenpv/xen_machine_pv.c           |  7 +------
>   10 files changed, 35 insertions(+), 58 deletions(-)
> 

Re: [PATCH v2 0/7] hw/xen: Simplify legacy backends handling

[Philippe Mathieu-Daudé]

On 10/5/24 12:49, Philippe Mathieu-Daudé wrote:
> Respin of Paolo's Xen patches from
> https://lore.kernel.org/qemu-devel/20240509170044.190795-1-pbonzini@redhat.com/
> rebased on one of my cleanup branches making backend
> structures const. Treat xenfb as other backends.
> 
> Paolo Bonzini (2):
>    hw/xen: initialize legacy backends from xen_bus_init()
>    hw/xen: register legacy backends via xen_backend_init
> 
> Philippe Mathieu-Daudé (5):
>    hw/xen: Remove declarations left over in 'xen-legacy-backend.h'
>    hw/xen: Constify XenLegacyDevice::XenDevOps
>    hw/xen: Constify xenstore_be::XenDevOps
>    hw/xen: Make XenDevOps structures const
>    hw/xen: Register framebuffer backend via xen_backend_init()

Thanks Paul for the review, unfortunately Paulo missed this and
merged v1 as single commit 88f5ed7017 ("xen: register legacy
backends via xen_backend_init") :(

Regards,

Phil.