Hi On 12/27/2011 03:25 AM, Ajith Adapa wrote:
Hi, I am new to KVM stuff and had very BASIC (might be lame even) doubts regarding KVM. As per the various diagrams I have gone through in internet my understanding is KVM is an hypervisor on top of which all VMs run. In case of FULL VIRTUALIZATION .. KVM will be directly running on top of HARDWARE and VMs will be running on top of KVM . In that case we dont need any support of other linux modules or subsystems ? vm1 ... vmn -------------- | KVM | -------------- Hardware
Not in my experience. kvm is drivers on a host kernel which has other drivers in order to function (at least to boot) and a user-space (at least qemu instances). kvm does provide I/O virtualization to the extent that host devices you only want to be used in a guest can be ignored without host drivers and only operated from the guest as-if a guest device with guest drivers but there will still be things like I/O port access trapping and interrupts will happen on host processors at any juncture so presumably quickly routed by kvm behavior to service routines after switching to a suitable guest context, though I'm no expert on the code.
Actually I am very much intrested in networking component of virtualization. So does KVM provides any specific support for networking in case of virtualization ?
You can take a host NIC and use it's drivers in a guest to operate it. You can use tap interfaces for a guest and bridge them to host interfaces which can include bridged physical NICs or not and/or use host IP stack configuration to route guest traffic from its own IP network to any reachable by the host. On most of my kvm hosts I have bridges br0, br1 and br8 to simulate the vmnet0 (bridged - physical network access), vmnet1 (host only - isolated guests with host connectivity) and vmnet8 (NAT - routing from a host only network to anything reachable by the host) configurations you get on many default vmware configurations. I tried the I/O device virtualization quite a while ago and it wasn't reliable enough and, although I'm sure it's much improved, with the configuration I use I've never needed to try again.
Sorry if there is any developer guide for KVM will be more helpful for me.
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