Re: [Qemu-devel] [PATCH 0/2][RFC] postcopy migration: Linux char device for postcopy

[Isaku Yamahata]

On Thu, Dec 29, 2011 at 04:35:36PM +0200, Avi Kivity wrote:
> On 12/29/2011 04:18 PM, Isaku Yamahata wrote:
> > > >
> > > > The issue is how to solve the page fault, not whether 
> > > > TASK_INTERRUPTIBLE or
> > > > TASK_UNINTERRUPTIBLE.
> > > > I can think of several options.
> > > > - When daemon X is dead, all page faults are served by zero pages.
> > > > - When daemon X is dead, all page faults are resovled as VM_FAULT_SIGBUS
> > > > - list/reattach: complications. You don't like it
> > > > - other?
> > > 
> > > Don't resolve the page fault.  It's up to the user/system to make sure
> > > it happens.  qemu can easily do it by watching for the daemon's death
> > > and respawning it.
> > > 
> > > When the new daemon is started, it can ask the kernel for a list of
> > > pending requests, and service them.
> >
> > Great, then we agreed with list/reattach basically.
> > (Maybe identity scheme needs reconsideration.)
> 
> I guess we miscommunicated.  Why is reattach needed?  If you have the
> fd, nothing else is needed.

What if malicious process close the fd and does page fault intentionally?
Unkillable process issue remains.
I think we are talking not only qemu case but also general case.
-- 
yamahata