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xen-bus: only set the xen device frontend state if it is missing 

Some toolstack implementations will set the frontend xenstore
keys to Initialising which will then trigger the in guest PV
drivers to begin initialising and some implementations will
then set their state to Closing. If this has occurred then
device realize must not overwrite the frontend keys as then
the handshake will stall.

Signed-off-by: Mark Syms <mark.syms@citrix.com>

Also avoid creating the frontend area if it already exists.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190918115745.39006-1-paul.durrant@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Mark Syms 2019-09-18 12:57:44 +01:00 committed by Anthony PERARD
parent ef916ab3ec
commit 6bd6b955c0
1 changed files with 31 additions and 16 deletions
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47
hw/xen/xen-bus.c
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@ -857,6 +857,13 @@ static void xen_device_frontend_changed(void *opaque)
}
}
static bool xen_device_frontend_exists(XenDevice *xendev)
{
enum xenbus_state state;
return (xen_device_frontend_scanf(xendev, "state", "%u", &state) == 1);
}
static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
{
XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
@ -865,19 +872,25 @@ static void xen_device_frontend_create(XenDevice *xendev, Error **errp)
xendev->frontend_path = xen_device_get_frontend_path(xendev);
perms[0].id = xendev->frontend_id;
perms[0].perms = XS_PERM_NONE;
perms[1].id = xenbus->backend_id;
perms[1].perms = XS_PERM_READ | XS_PERM_WRITE;
/*
* The frontend area may have already been created by a legacy
* toolstack.
*/
if (!xen_device_frontend_exists(xendev)) {
perms[0].id = xendev->frontend_id;
perms[0].perms = XS_PERM_NONE;
perms[1].id = xenbus->backend_id;
perms[1].perms = XS_PERM_READ | XS_PERM_WRITE;
g_assert(xenbus->xsh);
g_assert(xenbus->xsh);
xs_node_create(xenbus->xsh, XBT_NULL, xendev->frontend_path, perms,
ARRAY_SIZE(perms), &local_err);
if (local_err) {
error_propagate_prepend(errp, local_err,
"failed to create frontend: ");
return;
xs_node_create(xenbus->xsh, XBT_NULL, xendev->frontend_path, perms,
ARRAY_SIZE(perms), &local_err);
if (local_err) {
error_propagate_prepend(errp, local_err,
"failed to create frontend: ");
return;
}
}
xendev->frontend_state_watch =
@ -1290,12 +1303,14 @@ static void xen_device_realize(DeviceState *dev, Error **errp)
xen_device_backend_set_online(xendev, true);
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);
if (!xen_device_frontend_exists(xendev)) {
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, true);
xen_device_frontend_set_state(xendev, XenbusStateInitialising, true);
}
xendev->exit.notify = xen_device_exit;
qemu_add_exit_notifier(&xendev->exit);