[Lguest] mercurial repo

[Rusty Russell]

On Thu, 2007-07-26 at 14:08 -0700, Zachary Amsden wrote:
> ron minnich wrote:
> > Next question. I do have a working patch to allow experts to set the
> > system call #. Really, though, it makes more sense to set this in
> > sysfs or via a per-guest ioctl or some such, right? What's the fix
> > here? Plan 9 port is done, but I do need this change among others.
> >   
> 
> Allowing one to set the system call # is a bad idea.  You can't allow it 
> to overlap with any host IRQ or architectural fault handler.  Because 
> Linux uses IPIs in high numbers, and 0-0x1f are architectural faults, 
> the only truly safe system call vector that you can dispatch is 0x80.

Yeah, I agree: if plan9 used 0x80 we'd be sweet.  Otherwise we have to
reserve it and allow the guest to override that IDT entry (unless we
want to let it #gp and reflect back, but that's so slow).

Hmm, I know AIX has a kernel-provided shlib which provides the system
call mechanism.  If plan9 has some similar mechanism, then that might be
neater than nasty lguest tricks...

Rusty.