How to use multiple uart in a virtual machine?

[Chan Kim]

Hello all,

 

After checking character device option for qemu invocation, https://www.qemu.org/docs/master/system/invocation.html#hxtool-6

I tried to add another uart for a modified arm64 virt machine (named ab21q).

So I added second uart like this  (in hw/arm/ab21q.c which is modified from hw/arm/virt.c,  using qemu-6.2.0)

create_uart(vms, AB21Q_UART, sysmem, serial_hd(0));

create_uart(vms, AB21Q_UART1, sysmem, serial_hd(1)); // second uart

    // AB21Q_UART and AB21Q_UART1 have their own address space and irq number

I added the command option

-chardev stdio,mux=on,id=char0 -serial chardev:char0 -serial chardev:char0

But qemu gives this error :

qemu-system-aarch64: cannot use stdio by multiple character devices

(BTW, I’m running from u-boot program for starting linux)

How can I add second uart and make the second uart output to appear in the stdio also?

Any comment or help will be much appreciated.

Thank you!

 

Chan Kim