Ed Swierk wrote:
After staring at the code implementing node devices in libvirt, I have decided that they're really neat, but I have no idea what they are for or how to use them.
Reading the API docs and searching libvir-list didn't help much, and the user documentation (http://libvirt.org/archnode.html and http://libvirt.org/formatnode.html) is a bit, err, high-level.
Can someone enlighten me?
--Ed
-- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Hi, Ed, I am not a libvirt developer, maybe I only talk about it with you under my understand, and I hope it is helpful to you. At first, it will be better if I explain simply libvirt's goal and some basic concept: 1.The goal of libvirt: to provide a common generic and stable layer to securely manage domains on a node. 2. what is the node? A node is a single physical machine, in other words, a node is a host and a domain is an instance of an operating system(also known guest) Node devices should be some devices on the host, such as PCI device, In my opinion, you may understand its function from the use, a group virsh comand can help you, for example: [root@dhcp-66-70-173 ~]# virsh help | grep node nodeinfo node information nodedev-list enumerate devices on this host nodedev-dumpxml node device details in XML nodedev-dettach dettach node device its device driver nodedev-reattach reattach node device its device driver nodedev-reset reset node device nodedev-create create a device defined by an XML file on the node nodedev-destroy destroy a device on the node 1. display host information [root@dhcp-66-70-173 ~]# virsh nodeinfo CPU model: x86_64 CPU(s): 2 CPU frequency: 2327 MHz CPU socket(s): 1 Core(s) per socket: 2 Thread(s) per core: 1 NUMA cell(s): 1 Memory size: 2014320 kB 2. display devices on the host [root@dhcp-66-70-173 ~]# virsh nodedev-list --tree computer | +-pci_8086_10bd | | | +-net_00_1e_4f_db_02_5c | +-pci_8086_244e +-pci_8086_2914 ...... 3. display specify device xml description [root@dhcp-66-70-173 ~]# virsh nodedev-dumpxml pci_8086_10bd <device> <name>pci_8086_10bd</name> <parent>computer</parent> <capability type='pci'> <domain>0</domain> <bus>0</bus> <slot>25</slot> <function>0</function> <product id='0x10bd'>82566DM-2 Gigabit Network Connection</product> <vendor id='0x8086'>Intel Corporation</vendor> </capability> </device> 4. dettach host device its device driver [root@dhcp-66-70-173 ~]# virsh nodedev-dettach pci_8086_10bd Device pci_8086_10bd dettached in fact, the operation hide the device host driver and bind the device to pci-stub driver [root@dhcp-66-70-173 ~]# readlink /sys/bus/pci/devices/0000\:00\:19.0/driver ../../../bus/pci/drivers/pci-stub 5. in order to return the device a certain&clean status, we need to reset the device [root@dhcp-66-70-173 ~]# virsh nodedev-reset pci_8086_10bd Device pci_8086_10bd reset 6. return the device from guest to host [root@dhcp-66-70-173 ~]# virsh nodedev-reattach pci_8086_10bd Device pci_8086_10bd re-attached From step 2 to step 6, this group operations is very useful, such as we pass through a host pci device to guest. Best Regards, Alex Jia