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To: Peter Wemm <peter@freefall.freebsd.org>
cc: freebsd-smp@freefall.freebsd.org
Subject: Re: cvs commit: sys/i386/isa vector.s 
In-reply-to: Your message of "Tue, 03 Dec 1996 18:47:00 PST."
             <199612040247.SAA00731@freefall.freebsd.org> 
Date: Wed, 04 Dec 1996 11:02:06 +0800
From: Peter Wemm <peter@spinner.dialix.com>
Sender: owner-smp@FreeBSD.ORG
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Peter Wemm wrote:
> peter       96/12/03 18:47:00
> 
>   Modified:    i386/isa  vector.s
>   Log:
>   Fix IPI_INTR handler code.  It was not setting %ds with the kernel
>   selector, so if it took an IPI while in user mode, it got a GPF when
>   trying to access kernel data.  (%cs is set by the hardware)

I'm not sure why this used to work before..  It should never have..  I
somehow suspect that this might be somehow related to the SMP_AUTOSTART
code that is now disabled.  I suspect all the tests were done while
it was unconditionally active.  This might be a clue as to what was going
wrong with the code..  It looks like %ds was always set to the kernel
data segment selector, even while in user mode on both cpu's.  This
would have been rather bad if so..  I have no idea how this could have
been caused though.

Cheers,
-Peter