Re: [kvm-devel] [PATCH][RFC] KVM: prepare user interface for smp guests

[Avi Kivity <avi@qumranet.com>]

Arnd Bergmann wrote:
> Separating the objects into different file descriptors sounds like a
> good idea, but reusing an open dentry/inode with a new file and different
> file operations is a rather unusual way to do it. 

Yes, it doesn't feel right.

> Your concept of allocating
> a new context on each open is already weird, but there have been other
> examples of that before.
>   

Actually that seemed to me quite natural.

> I'd suggest going to a syscall-based model with your own file system right
> away, even if you don't use the spufs approach but something in the middle:
>
> * You do a trivial nonmountable new file system with anonymous objects,
>   similar to eventpollfs, and hand out file descriptors to inodes in it,
>   for both the kvm and the vcpu objects.
> * You replace the syscall you'd normally use to hand out a new kvm instance
>   with an ioctl on /dev/kvm, and don't allow any other operations on that
>   device.
>
> This would be a much more consistant object model, compared with other
> generic kernel functionality that is not bound to an actual device.
> You still have all the flexibility of a loadable module without core
> kernel changes for the development phase, and can easily switch to real
> syscalls when merging it into mainline.
>   

I agree, that sounds like a good plan.  I'll look into it.

BTW, what does lsof show for spufs users?  I thought lsof /dev/kvm would 
be a good way to look for virtual machines.


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