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Date:      Sun, 25 May 2008 20:33:01 +1200
From:      Mark Kirkwood <markir@paradise.net.nz>
To:        John Baldwin <jhb@freebsd.org>
Cc:        freebsd-stable <freebsd-stable@freebsd.org>
Subject:   Re: BTX loader hangs after version info
Message-ID:  <4839243D.7000700@paradise.net.nz>
In-Reply-To: <48390FA9.5080503@paradise.net.nz>
References:  <720051dc0805220159n23eb6205yfcf9450be7af5c77@mail.gmail.com> <200805230829.09524.jhb@freebsd.org> <20080523132645.GO29770@deviant.kiev.zoral.com.ua> <200805231811.01936.jhb@freebsd.org> <48390FA9.5080503@paradise.net.nz>

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I wrote:
> John Baldwin wrote:
>>
>> Try this patch.  I'm not 100% certain this will fix it as I can't 
>> reproduce
>> the issue, but I think it might help.  Specifically, when the boot 
>> code makes
>> a v86 call, the loader/boot2/whatever swaps in/out a new set of 
>> registers via
>> the v86 structure including the eflags register.  However, none of 
>> the boot
>> programs actually initialized the v86 structure.   Thus, the BIOS 
>> routines
>> would start off running with whatever garbage was in v86.efl when 
>> each boot
>> program started.  This meant that we could end up invoking BIOS 
>> routines with
>> interrupts disabled, and I think this might explain a hard hang (if a 
>> BIOS
>> routine was waiting for an interrupt the interrupt would never 
>> fire).  The
>> patch fixes all the boot programs to initialize v86 to a better known 
>> state. At the least it sets v86.efl to a sane value (0x202) rather 
>> than random.  (The
>> random might have always been 0x0 BTW, not sure on that one.)
>>
>>   
> Thanks John,
>
> Unfortunately this patch does *not* cure the issue for my old 
> Supermicro P3TDDE, it still hangs just before presenting the menu. I 
> had to boot off the livefs and copy /boot/loader.old -> /boot/loader 
> to get back to being bootable again - but at least the old fella is on 
> a more up-to-date 7-STABLE now :-)

Given that the patch *did* cure Peters Tyan S2720, I'll double check I 
didn't fat finger applying the patch (mind you the Tyan has AMI BOIS - 
same as my Supermicro P3TDERs that *do* work ok with current 7-STABLE, 
whereas the P3TDDE has Award BIOS).

Anyway, I'll double check and report back...

Cheers

Mark



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