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Re: [Qemu-devel] [PULL 06/25] xen: create xenstore areas for XenDevice-s
On 4/2/20 11:49 AM, Paul Durrant wrote:
-----Original Message-----
From: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
Sent: 01 April 2020 17:14
To: Anthony PERARD <anthony.perard@xxxxxxxxxx>; qemu-devel@xxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Peter Maydell <peter.maydell@xxxxxxxxxx>;
Paul Durrant
<paul@xxxxxxx>; Markus Armbruster <armbru@xxxxxxxxxx>
Subject: Re: [Qemu-devel] [PULL 06/25] xen: create xenstore areas for
XenDevice-s
Hi Anthony, Paul.
Cc'ing Markus too.
On 1/14/19 2:51 PM, Anthony PERARD wrote:
From: Paul Durrant <paul.durrant@xxxxxxxxxx>
This patch adds a new source module, xen-bus-helper.c, which builds on
basic libxenstore primitives to provide functions to create (setting
permissions appropriately) and destroy xenstore areas, and functions to
'printf' and 'scanf' nodes therein. The main xen-bus code then uses
these primitives [1] to initialize and destroy the frontend and backend
areas for a XenDevice during realize and unrealize respectively.
The 'xen-block' implementation is extended with a 'get_name' method that
returns the VBD number. This number is required to 'name' the xenstore
areas.
NOTE: An exit handler is also added to make sure the xenstore areas are
cleaned up if QEMU terminates without devices being unrealized.
[1] The 'scanf' functions are actually not yet needed, but they will be
needed by code delivered in subsequent patches.
Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Reviewed-by: Anthony Perard <anthony.perard@xxxxxxxxxx>
Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
hw/block/xen-block.c | 9 +
hw/xen/Makefile.objs | 2 +-
hw/xen/trace-events | 12 +-
hw/xen/xen-bus-helper.c | 150 +++++++++++++++
hw/xen/xen-bus.c | 321 +++++++++++++++++++++++++++++++-
include/hw/xen/xen-bus-helper.h | 39 ++++
include/hw/xen/xen-bus.h | 12 ++
7 files changed, 540 insertions(+), 5 deletions(-)
create mode 100644 hw/xen/xen-bus-helper.c
create mode 100644 include/hw/xen/xen-bus-helper.h
[...]
+static void xen_device_exit(Notifier *n, void *data)
+{
+ XenDevice *xendev = container_of(n, XenDevice, exit);
+
+ xen_device_unrealize(DEVICE(xendev), &error_abort);
}
static void xen_device_realize(DeviceState *dev, Error **errp)
{
XenDevice *xendev = XEN_DEVICE(dev);
XenDeviceClass *xendev_class = XEN_DEVICE_GET_CLASS(xendev);
+ XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
const char *type = object_get_typename(OBJECT(xendev));
Error *local_err = NULL;
- trace_xen_device_realize(type);
+ if (xendev->frontend_id == DOMID_INVALID) {
+ xendev->frontend_id = xen_domid;
+ }
+
+ if (xendev->frontend_id >= DOMID_FIRST_RESERVED) {
+ error_setg(errp, "invalid frontend-id");
+ goto unrealize;
+ }
+
+ if (!xendev_class->get_name) {
+ error_setg(errp, "get_name method not implemented");
+ goto unrealize;
+ }
+
+ xendev->name = xendev_class->get_name(xendev, &local_err);
+ if (local_err) {
+ error_propagate_prepend(errp, local_err,
+ "failed to get device name: ");
+ goto unrealize;
+ }
+
+ trace_xen_device_realize(type, xendev->name);
+
+ xen_device_backend_create(xendev, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ goto unrealize;
+ }
+
+ xen_device_frontend_create(xendev, &local_err);
+ if (local_err) {
+ error_propagate(errp, local_err);
+ goto unrealize;
+ }
if (xendev_class->realize) {
xendev_class->realize(xendev, &local_err);
@@ -72,18 +364,43 @@ static void xen_device_realize(DeviceState *dev, Error
**errp)
}
}
+ xen_device_backend_printf(xendev, "frontend", "%s",
+ xendev->frontend_path);
+ xen_device_backend_printf(xendev, "frontend-id", "%u",
+ xendev->frontend_id);
+ xen_device_backend_printf(xendev, "online", "%u", 1);
+ xen_device_backend_printf(xendev, "hotplug-status", "connected");
+
+ xen_device_backend_set_state(xendev, XenbusStateInitWait);
+
+ xen_device_frontend_printf(xendev, "backend", "%s",
+ xendev->backend_path);
+ xen_device_frontend_printf(xendev, "backend-id", "%u",
+ xenbus->backend_id);
+
+ xen_device_frontend_set_state(xendev, XenbusStateInitialising);
+
+ xendev->exit.notify = xen_device_exit;
+ qemu_add_exit_notifier(&xendev->exit);
return;
unrealize:
xen_device_unrealize(dev, &error_abort);
It seems if unrealize() fails, the error stored in &local_err is never
reported. Not sure if this can be improved although.
In this case that's essentially a "don't care". We want to know why the realize
failed but if the unrealize fails something is probably pretty seriously screwed (hence
the error_abort).
OK. I was surprised by the singular pattern (which confuses Coccinelle
semantic transformations), but it works.
Thanks for the quick feedback Paul!
Regards,
Phil.
Paul
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