Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server

From: Gregory Haskins <[email-masked]>
Date: Thu, 24 Sep 2009 14:04:34 -0400

Avi Kivity wrote:
> On 09/23/2009 10:37 PM, Avi Kivity wrote:
>>
>> Example: feature negotiation.  If it happens in userspace, it's easy
>> to limit what features we expose to the guest.  If it happens in the
>> kernel, we need to add an interface to let the kernel know which
>> features it should expose to the guest.  We also need to add an
>> interface to let userspace know which features were negotiated, if we
>> want to implement live migration.  Something fairly trivial bloats
>> rapidly.
> 
> btw, we have this issue with kvm reporting cpuid bits to the guest. 
> Instead of letting kvm talk directly to the hardware and the guest, kvm
> gets the cpuid bits from the hardware, strips away features it doesn't
> support, exposes that to userspace, and expects userspace to program the
> cpuid bits it wants to expose to the guest (which may be different than
> what kvm exposed to userspace, and different from guest to guest).
> 

This issue doesn't exist in the model I am referring to, as these are
all virtual-devices anyway.  See my last reply

-Greg