Re: KGDB on virt68k?

[Jason Thorpe <thorpej%me.com@localhost>]

> On Apr 27, 2026, at 3:45 PM, Chris Hanson <cmhanson%eschatologist.net@localhost> wrote:
> 
> I don't know the syntax to create another Goldfish tty on the QEMU command line, but it looks like it should be possible: The Android docs for the QEMU Goldfish devices say that serial device IDs are "0 to N" and that the Android emulator reserves the first *two* ports. I think that's expected to be passed to the kernel via the device tree; I don't know whether that's supported by the QEMU virt platform, or by NetBSD virt68k.

Well, there is not (yet) any device tree support in the m68k universe.  Qemu 68k virt platform provides all of that info to the kernel using Linux/68k-style “bootinfo”, which can pass more than one BI_VIRT_GF_TTY_BASE record to the kernel (the kernel uses the first one for the console).

> I do know I can one or more pairs like this
> 
>    -serial tcp:localhost:4000,server,nowait,id="kgdb" \
>    -device virtio-serial-device,id="kgdb" \
> 
> on the QEMU command line and VirtIO consoles are detected
> 
>    [   1.0000000] virtio0 at mainbus0 addr 0xff01f600
>    [   1.0000000] virtio0: VirtIO-MMIO-v2
>    [   1.0000000] virtio0: console device (id 3, rev. 0x01)
>    [   1.0000000] viocon0 at virtio0: features: 0x110000000<V1,INDIRECT_DESC>
>    [   1.0000000] virtio0: interrupting at gfpic4 irq 28 (IPL 5)
> 
> and I can connect to the port via telnet or nc. So maybe VirtIO serial might be a better approach for KGDB. (I assume if I create an appropriate node in /dev and run getty on it that I'd be able to connect to that port and get a login...)

Yah, should:

device-major viocon    char 364            viocon

-- thorpej