# [Solved] Linux Kernel KVM Host and Guest Config

## chris.c.hogan

I've been using KVM for a while now. However, I do not understand some of the kernel configuration options. I'm not sure which options are for the host side, for the guest side, or for both sides. I'm running the same OS (Gentoo kernel 3.4.9) on both sides and want to take advantage of any code that boosts performance. For example, I'm using the virtio devices.

https://wiki.archlinux.org/index.php/KVM suggests:

On the Host side:

```
kvm_intel (or kvm_amd. However, I have an Intel).
```

On the Guest side:

```
virtio_pci, virtio_blk, virtio_net, and virtio_ring
```

http://en.gentoo-wiki.com/wiki/KVM says nothing about client configuration. However, for host, it suggests:

```
<M>   KVM for Intel processors support

[*]   KVM paravirtualized clock

[*]   KVM Guest support

-*-   Enable paravirtualization code

[*]     Paravirtualization layer for spinlocks

[*] Enable KSM for page merging
```

http://wiki.gentoo.org/wiki/KVM for the host and http://wiki.gentoo.org/wiki/QEMU/Linux_guest for the guest suggests:

On the Host side:

```
<*>     KVM for Intel processors support

<*>   Host kernel accelerator for virtio net
```

On the Guest side:

```
[*]   KVM paravirtualized clock

[*]   KVM Guest support

<*>   PCI driver for virtio devices

<*>   Virtio block driver

<*>   Virtio network driver
```

http://forums.funtoo.org/viewtopic.php?id=1581 provides the following Guest suggestions:

```
CONFIG_VIRTIO_BLK=y

CONFIG_SCSI_VIRTIO=y

CONFIG_VIRTIO_NET=y

CONFIG_VIRTIO_CONSOLE=y

CONFIG_HW_RANDOM_VIRTIO=y

CONFIG_VIRTIO=y

CONFIG_VIRTIO_RING=y

CONFIG_VIRTIO_PCI=y

CONFIG_VIRTIO_BALLOON=y

CONFIG_VIRTIO_MMIO=y
```

My question mainly revolves around KVM paravirtualized clock and KVM Guest support. The kernel description of the clock says  *Quote:*   

> when running over the KVM hypervisor.

  and Guest support says  *Quote:*   

> for running under the KVM hypervisor.

 

Both suggest to me that this is something that should be configured on the guest. However, from above, I found references that show them configured on the host, and several that didn't show them configured at all. So, which kernel options should be set up on the host, which the guest, and which (if any) on both?

Thanks for any suggestions or clarifications. Documentation on KVM is confusing...Last edited by chris.c.hogan on Fri Oct 19, 2012 1:56 am; edited 1 time in total

----------

## Ant P.

 *chris.c.hogan wrote:*   

> http://en.gentoo-wiki.com/wiki/KVM says nothing about client configuration. However, for host, it suggests:
> 
> ```
> <M>   KVM for Intel processors support
> 
> ...

 

The page is wrong, you don't need kvm-clock or any guest options enabled on the host.

----------

## chris.c.hogan

 *Quote:*   

> you don't need kvm-clock or any guest options enabled on the host

  Thanks for the info. I wasn't sure if maybe there was some component that needed to be run on the host. However, it seems to run just fine as you said.

Thanks again!

----------

