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Re: [Qemu-discuss] Accessing both uart of machine -virt (aarch64)

From: Peter Maydell
Subject: Re: [Qemu-discuss] Accessing both uart of machine -virt (aarch64)
Date: Mon, 12 Jun 2017 19:38:44 +0100

On 12 June 2017 at 16:58, Vincent <address@hidden> wrote:
> Hi !
> I'm trying to test a bare metal aarch64 OS using qemu 'virt' machine.
> So far I'm only running the EL3 part of the OS.
> I am using the following command line to start qemu:
> qemu-system-aarch64 -machine virt,secure=on -cpu cortex-a57 \
>     -smp 1 -m 4096 -kernel my_kernel.elf -serial stdio
> When I access the VIRT_UART device, I can see my prints on the standard
> output of my console, but if I access the VIRT_SECURE_UART, I don't see
> anything.

You need another -serial option to say where it should go
(I think by default it will go to a tab in the graphics window).

> Can I redirect both uart to the same output (stdio) ?

Only by using the 'multiplexer' which is the thing that lets
you use C-a c and so on to switch between multiple outputs on
the same stdio (usually used for monitor and serial). You won't
see the output from both at once, but you can flip between them
with C-a c. This is documented in the manual:

but roughly speaking you would want
  -chardev stdio,mux=on,id=char0 \
  -serial chardev:char0 \
  -serial chardev:char0

to just mux the two serial outputs. Alternatively you can direct
the second serial to a TCP port or wherever else is convenient.

-- PMM

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