From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <ee9e417a0504182119175563d8@mail.gmail.com>
Date: Tue, 19 Apr 2005 00:19:27 -0400
From: Russ Cox <russcox@gmail.com>
To: 9fans <9fans@cse.psu.edu>
Subject: Re: [9fans] Plan9/Bochs/kernel panic
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References: <E1AJZHY-000Kxn-Jl@t40.swtch.com>
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On 11/11/03, Russ Cox <rsc@swtch.com> wrote:
> I tracked this down.  It seems to be a bug in Bochs.
> Real processors all let us turn off the FPU twice,
> but if the FPU is already off, then Bochs causes an
> exception when we "FWAIT" before turning it off again.

I tracked this down again (I had quite a sense of deja vu
once I found the problem, but google failed me and I hadn't
thought to look in my gmail).  This time I fixed Plan 9 to
work around it.  There is a new /sys/src/9/pc/l.s on sources
that avoids the FWAIT when the FPU is already off.
With that change, Plan 9 boots in Bochs, though I
suggest qemu with the kqemu module unless you
are doing OS hacking and need Bochs's better debugging
features.

Russ