Re: [PATCH 0/2] Make local migration with TAP network device possible

[Daniel P . Berrangé]

On Tue, Jun 14, 2022 at 02:18:41PM +0300, Andrey Ryabinin wrote:
> Hi
> 
> These couple patches aims to  make possible local migration (within one host)
> on the same TAP device used by source and destination QEMU
> 
> The scenario looks like this
>  1. Create TAP devices and pass file descriptors to source QEMU
>  2. Launch destination QEMU (-incoming defer) and pass same descriptors to it.
>  3. Start migration
> 
> 
> Regarding the first patch: It makes possible to receive file descriptor in 
> non-blocking
> state. But I probably didn't cover all FD users which might need to set 
> blocking state after
> the patch. So I'm hopping for the hints where else, besides 
> fd_start_incoming_migration()
> I need to put qemu_socket_set_block() calls.

You'll need to check all callers of

qio_channel_readv_full
qio_channel_readv_full_all
qio_channel_readv_full_all_eof

and identify which pass a non-NULL parameter for 'fds'. If the caller
does NOT have a qemu_setnonblock call on the FD it gets back, then you
have to assume it is expecting it in blocking mode and so need to
add qemu_setblock


With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|