Re: [Qemu-devel] [PATCH v7 37/42] Postcopy; Handle userfault requests

[Juan Quintela]

"Dr. David Alan Gilbert" <address@hidden> wrote:
> * Juan Quintela (address@hidden) wrote:
>> "Dr. David Alan Gilbert (git)" <address@hidden> wrote:
>> > From: "Dr. David Alan Gilbert" <address@hidden>
>> >
>> > 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 <address@hidden>
>> 
>> 
>> > @@ -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 / address@hidden / Manchester, UK

Reviewed-by: Juan Quintela <address@hidden>