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

From: Gregory Haskins <[email-masked]>
Date: Fri, 11 Sep 2009 12:14:07 -0400

Gregory Haskins wrote:

[snip]

> 
> FWIW: VBUS handles this situation via the "memctx" abstraction.  IOW,
> the memory is not assumed to be a userspace address.  Rather, it is a
> memctx-specific address, which can be userspace, or any other type
> (including hardware, dma-engine, etc).  As long as the memctx knows how
> to translate it, it will work.
> 

citations:

Here is a packet import (from the perspective of the host side "venet"
device model, similar to Michaels "vhost")

http://git.kernel.org/?p=linux/kernel/git/ghaskins/alacrityvm/linux-2.6.git;a=blob;f=kernel/vbus/devices/venet-tap.c;h=ee091c47f06e9bb8487a45e72d493273fe08329f;hb=ded8ce2005a85c174ba93ee26f8d67049ef11025#l535

Here is the KVM specific memctx:

http://git.kernel.org/?p=linux/kernel/git/ghaskins/alacrityvm/linux-2.6.git;a=blob;f=kernel/vbus/kvm.c;h=56e2c5682a7ca8432c159377b0f7389cf34cbc1b;hb=ded8ce2005a85c174ba93ee26f8d67049ef11025#l188

and

http://git.kernel.org/?p=linux/kernel/git/ghaskins/alacrityvm/linux-2.6.git;a=blob;f=virt/kvm/xinterface.c;h=0cccb6095ca2a51bad01f7ba2137fdd9111b63d3;hb=ded8ce2005a85c174ba93ee26f8d67049ef11025#l289

You could alternatively define a memctx for your environment which knows
how to deal with your PPC boards PCI based memory, and the devices would
all "just work".

Kind Regards,
-Greg