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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Sat, 27 Aug 2022 08:32:44 +0200
Message-ID: <CAMj1kXEqF_wKibwvdXVzjBfLrTJpXquNLOyuQVrbF+ZyNvLDaA@mail.gmail.com>
Subject: Re: [PATCH] wait_on_bit: add an acquire memory barrier
To:     Mikulas Patocka <mpatocka@redhat.com>
Cc:     Will Deacon <will@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alan Stern <stern@rowland.harvard.edu>,
        Andrea Parri <parri.andrea@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Akira Yokosawa <akiyks@gmail.com>,
        Daniel Lustig <dlustig@nvidia.com>,
        Joel Fernandes <joel@joelfernandes.org>,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
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On Fri, 26 Aug 2022 at 21:10, Mikulas Patocka <mpatocka@redhat.com> 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)