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Date: Tue, 14 Jul 2015 16:15:39 +0100
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Message-ID: <20150714151538.GA13856@work-vm>
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Subject: Re: [Qemu-devel] [PATCH v7 37/42] Postcopy;
	Handle userfault requests
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To: Juan Quintela <quintela@redhat.com>
Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >
> > userfaultfd is a Linux syscall that gives an fd that receives a stream
> > of notifications of accesses to pages registered with it and allows
> > the program to acknowledge those stalls and tell the accessing
> > thread to carry on.
> >
> > We convert the requests from the kernel into messages back to the
> > source asking for the pages.
> >
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> 
> 
> > @@ -274,15 +276,41 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
> >   */
> >  int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
> >  {
> > -    /* TODO: Join the fault thread once we're sure it will exit */
> > -    if (qemu_ram_foreach_block(cleanup_area, mis)) {
> > -        return -1;
> > +    trace_postcopy_ram_incoming_cleanup_entry();
> > +
> > +    if (mis->have_fault_thread) {
> > +        uint64_t tmp64;
> > +
> > +        if (qemu_ram_foreach_block(cleanup_area, mis)) {
> > +            return -1;
> > +        }
> > +        /*
> > +         * Tell the fault_thread to exit, it's an eventfd that should
> > +         * currently be at 0, we're going to inc it to 1
> > +         */
> > +        tmp64 = 1;
> > +        if (write(mis->userfault_quit_fd, &tmp64, 8) == 8) {
> > +            trace_postcopy_ram_incoming_cleanup_join();
> > +            qemu_thread_join(&mis->fault_thread);
> > +        } else {
> > +            /* Not much we can do here, but may as well report it */
> > +            error_report("%s: incing userfault_quit_fd: %s", __func__,
> > +                         strerror(errno));
> 
> "incing"???

Oh, incrementing :-)
Changed.

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK