On Thu, Mar 21, 2019 at 06:28:41PM -0400, Laine Stump wrote:
qemuDomainDetachControllerDevice() calls
qemuDomainDetachExtensionDevice() when the *controller* type is
PCI. This is incorrect in multiple ways:
* Any code that tears down a device should be in the
qemuDomainRemove*Device() function (which is called after libvirt
gets a DEVICE_DELETED event from qemu indicating that the guest is
finished with the device on its end. The qemuDomainDetach*Device()
functions should only contain code that ensures the requested
operation is valid, and sends the command to qemu to initiate the
unplug.
* qemuDomainDetachExtensionDevice() is a function that applies to
devices that plug into a PCI slot, *not* necessarily PCI controllers
(which is what's being checked in the offending code). The proper
way to check for this would be to see if the DeviceInfo for the
controller device had a PCI address, not to check if the controller
is a PCI controller (the code being removed was doing the latter).
* According to commit 1d1e264f1 that added this code (and other
support for hotplugging zPCI devices on s390), it's not necessary to
explicitly detach the zPCI device when unplugging a PCI device. To
quote:
There's no need to implement hot unplug for zPCI as QEMU
implements an unplug callback which will unplug both PCI and
zPCI device in a cascaded way.
and the evidence bears this out - all the other uses of
qemuDomainDetachExtensionDevice() (except one, which I believe is
also in error, and is being removed in a separate patch) are only to
remove the zPCI extension device in cases where it was successfully
added, but there was some other failure later in the hotplug process
(so there was no regular PCI device to remove and trigger removal of
the zPCI extension device).
* PCI controllers are not hot pluggable, so this is dead code
You would have had me convinced at 'dead code'
anyway. (The only controllers that can currently be hotplugged/unplugged are SCSI controllers). Signed-off-by: Laine Stump <laine@xxxxxxxxx> --- src/qemu/qemu_hotplug.c | 12 ------------ 1 file changed, 12 deletions(-)
Reviewed-by: Ján Tomko <jtomko@xxxxxxxxxx> Jano
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