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8c9a600457
virHostdevReAttachPCIDevices() is called when we want to re-attach a list of hostdevs back to the host, either on the shutdown path or via a 'virsh detach-device' call. This function always count on the existence of the device in the host to work, but this can lead to problems. For example, a SR-IOV device can be removed via an admin "echo 0 > /sys/bus/pci/devices/<addr>/sriov_numvfs", making the kernel fire up and eventfd_signal() to the process, asking for the process to release the device. The result might vary depending on the device driver and OS/arch, but two possible outcomes are: 1) the hypervisor driver will detach the device from the VM, issuing a delete event to Libvirt. This can be observed in QEMU; 2) the 'echo 0 > ...' will hang waiting for the device to be unplugged. This means that the VM process failed/refused to release the hostdev back to the host, and the hostdev will be detached during VM shutdown. Today we don't behave well for both cases. We'll fail to remove the PCI device reference from mgr->activePCIHostdevs and mgr->inactivePCIHostdevs because we rely on the existence of the PCI device conf file in the sysfs. Attempting to re-utilize the same device (assuming it is now present back in the host) can result in an error like this: $ ./run tools/virsh start vm1-sriov --console error: Failed to start domain vm1-sriov error: Requested operation is not valid: PCI device 0000:01:00.2 is in use by driver QEMU, domain vm1-sriov For (1), a VM destroy/start cycle is needed to re-use the VF in the guest. For (2), the effect is more nefarious, requiring a Libvirtd daemon restart to use the VF again in any guest. We can make it a bit better by checking, during virHostdevReAttachPCIDevices(), if there is any missing PCI device that will be left behind in activePCIHostdevs and inactivePCIHostdevs lists. Remove any missing device found from both lists, unconditionally, matching the current state of the host. This change affects the code path in (1) (processDeviceDeletedEvent into qemuDomainRemoveDevice, all the way back to qemuHostdevReAttachPCIDevices) and also in (b) (qemuProcessStop into qemuHostdevReAttachDomainDevices). NB: Although this patch enables the possibility of 'outside Libvirt' SR-IOV hotunplug of PCI devices, if the hypervisor and the PCI driver copes with it, our goal is to mitigate what it is still considered a user oopsie. For all supported purposes, the admin must remove the SR-IOV VFs from all running domains before removing the VFs from the host. Resolves: https://gitlab.com/libvirt/libvirt/-/issues/72 Reviewed-by: Laine Stump <laine@redhat.com> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> |
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==============================
Libvirt API for virtualization
==============================
Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the
website:
https://libvirt.org
License
=======
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.
Installation
============
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
============
The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
=======
The libvirt project has two primary mailing lists:
* libvirt-users@redhat.com (**for user discussions**)
* libvir-list@redhat.com (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html