Re: [Qemu-devel] [Qemu-arm] [PATCH] hw/arm/virt: support 4 serial ports

["Jason A. Donenfeld" <Jason@zx2c4.com>]

On Thu, Oct 26, 2017 at 6:41 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
> Those are primarily about migration compatibility -- you should
> be able to live migrate a guest from QEMU 2.6's virt-2.6 machine to
> QEMU 2.7's virt-2.6 machine. That's a stricter requirement than
> the compatibility we want to keep for non-versioned machines,
> where generally we don't want to break command lines but are OK
> to make changes if they don't break those existing uses.
>
> Command lines get baked into all sorts of scripts and so they're
> effectively part of QEMU's "ABI". People don't like it when we
> break their previously working flows :-)

Fair enough. So in that case, secure=no means serials 1-4 are for
kernel. With secure=yes, serials 1,3-5 are for kernel, with serial 2
being for trustzone. Seems like that's the best of all worlds.