Re: [PATCH] wait_on_bit: add an acquire memory barrier

[Ard Biesheuvel]

On Fri, 26 Aug 2022 at 21:10, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
>
>
>
> On Fri, 26 Aug 2022, Ard Biesheuvel wrote:
>
> > Could you try booting with earlycon?
> >
> > Just 'earlycon' and if that does not help,
>
> It doesn't help.
>
> > 'earlycon=uart8250,mmio32,<uart PA>' [IIRC, mcbin uses 16550
> > compatible UARTs, right?]
>
> mcbin is the host system (running a stable kernel fine). The crash happens
> in a virtual machine. The vm uses /dev/ttyAMA0 as a console:
>
> Serial: AMBA PL011 UART driver
> 9000000.pl011: ttyAMA0 at MMIO 0x9000000 (irq = 45, base_baud = 0) is a PL011 rev1
> printk: console [ttyAMA0] enabled
>
> I tried earlycon=pl011,mmio32,0x9000000 - but it doesn't help, it hangs
> without printing anything.
>

If you are using pl011, you should drop the mmio32 - it only takes a
physical address (and optionally baud rate etc, but QEMU doesn't need
those)