Re: shared memory between host and VMs (windows xp) using virtio

[Avi Kivity <avi@redhat.com>]

On 10/23/2009 11:29 AM, Nev wrote:
> I need to be able to share memory between guest VMs and the host. I have
> been using VMware workstation 6.0.5. As Cam Macdonell stated in one of
> his posts, VMware dropped the shared memory as part of their VMCI
> interface in later versions. I am the person he refered to in his post
> that is running simulation across multiple VMs.
>
> My requirements are different from Cam's.
> 1. I need to be able to dynamically allocate multiple blocks of shared
> memory of different sizes. Size of each shared block can vary from a few
> bytes to a few MBytes
> 2. I need to be able to have any number of Guest, include zero, and any
> number of host processes, including zero, sharing the memory.
> 3. The virtual address used to access the memory *can* be different for
> each host process and guest process. eg no requirements
> 4. I dont need interrupts.
>    

Probably best served with a single shared area with an internal memory 
allocator.

> I *think* I will need a host kernel module (device drive?) to service
> the requests.
> The module needs to be accessible from use level host code, and user
> guest code via a Guest device driver, or service and then via virtio to
> the host module.
>
>    

No need for host kernel modifications (as Cam's work shows).

> I am assuming there is little or no documentation for virtio, and I need
> to look at the code.
>
> I would like a little help to get started.
> 1. Should I be looking at quemu-kvm or kvm or somewhere else?
> 2. Can I get some hints at what function to look for and where?
> 3. If there is any documentation please indicate where I might find it.
>    

virtio is mostly useful for dynamic dma from guest memory; for static 
sharing of host memory it isn't a good fit.

> I would prefer to *not* modify the existing kvm code, but would prefer
> to write stand allow modules that interface to the kvm code. I will be
> happy to make the source for these modules publicly available.
>
> Any help will be greatly appreciated.
>    

Best starting point is Cam's patches, IMO.

-- 
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