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From: Ian Lepore <freebsd@damnhippie.dyndns.org>
To: Adrian Chadd <adrian@freebsd.org>
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Date: Wed, 19 Sep 2012 15:05:06 -0600
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Cc: lev@freebsd.org, freebsd-current@freebsd.org
Subject: Re: Latest -CURRENT/i386 could not start under VirutalBox 4.1.18
 and 4.2 (Windows host): hangs up after atrtc0 detection
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On Wed, 2012-09-19 at 14:00 -0700, Adrian Chadd wrote:
> On 19 September 2012 13:54, Lev Serebryakov <lev@freebsd.org> wrote:
> > Hello, Ian.
> > You wrote 20 сентября 2012 г., 0:46:24:
> >
> > IL> Yes, exactly.  I updated the PR to request that my patch not get
> > IL> committed because it locks up virtualbox.  I hope to find time soon to
> > IL> learn enough about installing/configuring virtualbox to figure out what
> > IL> the problem is (offhand,I suspect it hangs in the loop that probes for
> > IL> the need to re-index, because vbox doesn't quite emulate the hardware
> > IL> behavior fully).
> >  How could I help? Is it possible to debug kernel on such early stage?
> 
> Add something to atrtc_start() to only loop over that loop say, 64k
> times before dropping out; and print an error if it hits that
> condition.
> 
> Also, what's that RTCSA_8192 bit do?

That should set the interrupt rate really high, to minimize the time
wasted waiting for the status bit to change in the register.  Maybe
that's the part that vbox isn't emulating well and so it never simulates
an interrupt and leaves that loop.  Or maybe because the loop is a tight
busy-wait the emulator never gets control to simulate the occurance of
the interrupt.

-- Ian