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

From: Gregory Haskins <gregory.haskins@gmail.com>
To: Avi Kivity <avi@redhat.com>
Cc: "Ira W. Snyder" <iws@ovro.caltech.edu>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	netdev@vger.kernel.org,
	virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org,
	akpm@linux-foundation.org, hpa@zytor.com,
	Rusty Russell <rusty@rustcorp.com.au>,
	s.hetze@linux-ag.com, alacrityvm-devel@lists.sourceforge.net
Subject: Re: [PATCHv5 3/3] vhost_net: a kernel-level virtio server
Date: Thu, 24 Sep 2009 14:04:34 -0400	[thread overview]
Message-ID: <4ABBB4B2.7050404@gmail.com> (raw)
In-Reply-To: <4ABB27B9.4050904@redhat.com>

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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

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