i386/151122: [boot] BTX 1.02 crashes on boot

[Guido Falsi]

The following reply was made to PR i386/151122; it has been noted by GNATS.

From: Guido Falsi <mad at madpilot.net>
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: i386/151122: [boot] BTX 1.02 crashes on boot
Date: Fri, 17 Jun 2011 16:46:39 +0200

 By disassembling the BIOS function mentioned above in this PC and
 another HP one on which FreeBSD hass no problems I could find one main
 difference.
 
 On the 8005Pro the BIOS works with the cr[034] and MSR control
 registers, while in another BIOS the function is performed without
 touching those.
 
 Reading the history of BTX in cvs I see the old BTX 1.01 used to emulate
 such accesses through exceptions, the new one gives full control to the
 BIOS so I'm quite lost on why there should be such a regression.
 
 I have the disassebled code which modifies the CRs if nyone should need
 to look at it. (Not sure about policies for posting such things on gnats
 so I play it safe)
 
 -- 
 Guido Falsi <mad at madpilot.net>