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The only way object_property_add() can fail is when a property with
the same name already exists. Since our property names are all
hardcoded, failure is a programming error, and the appropriate way to
handle it is passing &error_abort.
Same for its variants, except for object_property_add_child(), which
additionally fails when the child already has a parent. Parentage is
also under program control, so this is a programming error, too.
We have a bit over 500 callers. Almost half of them pass
&error_abort, slightly fewer ignore errors, one test case handles
errors, and the remaining few callers pass them to their own callers.
The previous few commits demonstrated once again that ignoring
programming errors is a bad idea.
Of the few ones that pass on errors, several violate the Error API.
The Error ** argument must be NULL, &error_abort, &error_fatal, or a
pointer to a variable containing NULL. Passing an argument of the
latter kind twice without clearing it in between is wrong: if the
first call sets an error, it no longer points to NULL for the second
call. ich9_pm_add_properties(), sparc32_ledma_realize(),
sparc32_dma_realize(), xilinx_axidma_realize(), xilinx_enet_realize()
are wrong that way.
When the one appropriate choice of argument is &error_abort, letting
users pick the argument is a bad idea.
Drop parameter @errp and assert the preconditions instead.
There's one exception to "duplicate property name is a programming
error": the way object_property_add() implements the magic (and
undocumented) "automatic arrayification". Don't drop @errp there.
Instead, rename object_property_add() to object_property_try_add(),
and add the obvious wrapper object_property_add().
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200505152926.18877-15-armbru@redhat.com>
[Two semantic rebase conflicts resolved]
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Introduces hot plug/unplug support for the vfio-ap device.
To hot plug a vfio-ap device using the QEMU device_add command:
(qemu) device_add vfio-ap,sysfsdev=$path-to-mdev
Where $path-to-mdev is the absolute path to the mediated matrix device
to which AP resources to be used by the guest have been assigned.
A vfio-ap device can be hot plugged only if:
1. A vfio-ap device has not been attached to the virtual machine's ap-bus
via the QEMU command line or a prior hot plug action.
2. The guest was started with the CPU model feature for AP enabled
(e.g., -cpu host,ap=on)
To hot unplug a vfio-ap device using the QEMU device_del command:
(qemu) device_del vfio-ap,sysfsdev=$path-to-mdev
Where $path-to-mdev is the absolute path to the mediated matrix device
specified when the vfio-ap device was attached to the virtual machine's
ap-bus.
A vfio-ap device can be hot unplugged only if:
1. A vfio-ap device has been attached to the virtual machine's ap-bus
via the QEMU command line or a prior hot plug action.
2. The guest was started with the CPU model feature for AP enabled
(e.g., -cpu host,ap=on)
Please note that a hot plug handler is not necessary for the vfio-ap device
because the AP matrix configuration for the guest is performed by the
kernel device driver when the vfio-ap device is realized. The vfio-ap device
represents a VFIO mediated device created in the host sysfs for use by a guest.
The mdev device is configured with an AP matrix (i.e., adapters and domains) via
its sysfs attribute interfaces prior to starting the guest or plugging a vfio-ap
device in. When the device is realized, a file descriptor is opened on the mdev
device which results in a callback to the vfio_ap kernel device driver. The
device driver then configures the AP matrix in the guest's SIE state description
from the AP matrix assigned via the mdev device's sysfs interfaces. The AP
devices will be created for the guest when the AP bus running on the guest
subsequently performs its periodic scan for AP devices.
The qdev_simple_device_unplug_cb() callback function is used for the same
reaons; namely, the vfio_ap kernel device driver will perform the AP resource
de-configuration for the guest when the vfio-ap device is unplugged. When the
vfio-ap device is unrealized, the mdev device file descriptor is closed which
results in a callback to the vfio_ap kernel device driver. The device driver
then clears the AP matrix configuration in the guest's SIE state description
and resets all of the affected queues. The AP devices created for the guest
will be removed when the AP bus running on the guest subsequently performs
its periodic scan and finds there are no longer any AP resources assigned to the
guest.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Tested-by: Pierre Morel <pmorel@linux.ibm.com>
Message-Id: <1550519397-25359-2-git-send-email-akrowiak@linux.ibm.com>
[CH: adapt to changed qbus_set_hotplug_handler() signature]
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
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