Re: [RFC PATCH v3 1/6] kvm: add device control API

[Gleb Natapov <gleb@redhat.com>]

On Fri, Apr 05, 2013 at 12:02:06PM +1100, Paul Mackerras wrote:
> On Thu, Apr 04, 2013 at 01:41:35PM +0300, Gleb Natapov wrote:
> 
> > Since now each device has its own fd is it an advantage to enforce
> > common interface between different devices? If we do so though why
> > not handle file creation, ioctl and file descriptor lifetime in the
> > common code. Common code will have "struct kvm_device" with "struct
> > kvm_device_arch" and "struct kvm_device_ops" members. Instead of
> > kvm_mpic_ioctl there will be kvm_device_ioctl which will despatch ioctls
> > to a device using kvm_device->ops->(set|get|has)_attr pointers.
> 
> I thought about making the same request, but when I looked at it, the
> amount of code that could be made common in this way is pretty tiny,
> and doing that involves a bit of extra complexity, so I thought that
> on the whole it wouldn't be worthwhile.
> 
The value of doing so is not only in making some code common, but also
moving fd lifetime management into the common code where it can be
debugged once and for all potential users. I also expect the amount of
shared code to grow when interface will be used by more architectures.

--
			Gleb.