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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <1434450415-11339-38-git-send-email-dgilbert@redhat.com> (David
	Alan Gilbert's message of "Tue, 16 Jun 2015 11:26:50 +0100")
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	<1434450415-11339-38-git-send-email-dgilbert@redhat.com>
Date: Tue, 14 Jul 2015 17:10:42 +0200
Message-ID: <87h9p6g4gd.fsf@neno.neno>
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Subject: Re: [Qemu-devel] [PATCH v7 37/42] Postcopy;
	Handle userfault requests
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To: "Dr. David Alan Gilbert (git)" <dgilbert@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

"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"???