Re: [Qemu-devel] [PATCH v7 27/42] postcopy: ram_enable_notify to switch on userfault

[Dr. David Alan Gilbert]

* Juan Quintela (address@hidden) wrote:
> "Dr. David Alan Gilbert (git)" <address@hidden> wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> >
> > Mark the area of RAM as 'userfault'
> > Start up a fault-thread to handle any userfaults we might receive
> > from it (to be filled in later)
> >
> > Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> > Reviewed-by: David Gibson <address@hidden>
> > ---
> >  include/migration/migration.h    |  3 ++
> >  include/migration/postcopy-ram.h |  6 ++++
> >  migration/postcopy-ram.c         | 69 
> > +++++++++++++++++++++++++++++++++++++++-
> >  migration/savevm.c               |  9 ++++++
> >  4 files changed, 86 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > index 98e2568..e6585c5 100644
> > --- a/include/migration/migration.h
> > +++ b/include/migration/migration.h
> > @@ -69,6 +69,9 @@ struct MigrationIncomingState {
> >       */
> >      QemuEvent      main_thread_load_event;
> >  
> > +    QemuThread     fault_thread;
> 
> Best name ever?  Well, it could be "wrong_thread" O:-)

Well they are 'user faults'!   Not that we blame the user for
them personally of course.

> > +static void *postcopy_ram_fault_thread(void *opaque)
> > +{
> > +    MigrationIncomingState *mis = (MigrationIncomingState *)opaque;
> 
> Uneeded cast.

Thanks, gone.

> > +
> > +    fprintf(stderr, "postcopy_ram_fault_thread\n");
> > +    /* TODO: In later patch */
> > +    qemu_sem_post(&mis->fault_thread_sem);
> > +    while (1) {
> > +        /* TODO: In later patch */
> > +    }
> > +
> > +    return NULL;
> > +}
> > +
> > +int postcopy_ram_enable_notify(MigrationIncomingState *mis)
> > +{
> > +    /* Create the fault handler thread and wait for it to be ready */
> > +    qemu_sem_init(&mis->fault_thread_sem, 0);
> > +    qemu_thread_create(&mis->fault_thread, "postcopy/fault",
> > +                       postcopy_ram_fault_thread, mis, 
> > QEMU_THREAD_JOINABLE);
> > +    qemu_sem_wait(&mis->fault_thread_sem);
> > +    qemu_sem_destroy(&mis->fault_thread_sem);
> > +
> > +    /* Mark so that we get notified of accesses to unwritten areas */
> > +    if (qemu_ram_foreach_block(ram_block_enable_notify, mis)) {
> > +        return -1;
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> >  #else
> >  /* No target OS support, stubs just fail */
> > -
> 
> This belongs in a different patch O:-)

Thanks, gone.

> If you have to resend, just change them.
> 
> Reviewed-by: Juan Quintela <address@hidden>

Dave

--
Dr. David Alan Gilbert / address@hidden / Manchester, UK