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[Xen-devel] Re: [RFC] [PATCH] sysfs support for Xen attributes

Greg KH wrote:

What exactly do the different ioctls do?  Do they have to be ioctls?
Can you use configfs or sysfs for most of the stuff there?
The canonical example is /proc/xen/privcmd which is our userspace hypercall interface. A hypercall is software interrupt with a number of parameters passed via registers. This has to come from ring 1 for security reasons (the kernel is running in ring 1).

We wish to make management hypercalls as the root user in userspace which means we have to go through the kernel. Currently, we do this by having /proc/xen/privcmd accept an ioctl() that takes a structure that describe the register arguments. The kernel interface allows us to control who in userspace can execute hypercalls.

It would perhaps be possible to use a read/write interface for hypercalls but ioctl() seems a little less awkward. Suggestions are certainly appreciated though.

Right now, I think a misc char device with an ioctl() interface seems like the most promising way to do this. This doesn't seem like the sort of think one would want to expose in sysfs...


Anthony Liguori


greg k-h
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