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Re: [PATCH 0/2] Make local migration with TAP network device possible
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH 0/2] Make local migration with TAP network device possible |
Date: |
Tue, 14 Jun 2022 12:32:22 +0100 |
User-agent: |
Mutt/2.2.1 (2022-02-19) |
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
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