amd64/111955: [install] Install CD boot panic due to missing BIOS smap on 5.5 through to 7.0-Current Snapshot 200704

[John Baldwin]

On Monday 18 February 2008 08:30:03 am Eamon.Roque at arf.fak12.uni-muenchen.de 
wrote:
> The following reply was made to PR amd64/111955; it has been noted by
> GNATS.
>
> From: Eamon.Roque at arf.fak12.uni-muenchen.de
> To: "John Baldwin" <jhb at freebsd.org>
> Cc: bug-followup at freebsd.org,
>     Eamon.Roque at arf.fak12.uni-muenchen.de
> Subject: Re: amd64/111955: [install] Install CD boot panic due to missing
>      BIOS smap on 5.5 through to 7.0-Current Snapshot 200704
> Date: Mon, 18 Feb 2008 14:06:53 +0100 (CET)
>
>  Would the amd64 kernel work the same way?
>
>  I was able to boot the x86 cds, although I had to specify the physical
>  memory size.
>
>  The amd64 8.0-Current bootonly cd from Feb.7, 2008 panics as before
>  because of the failed SMAP call.

The amd64 kernel assumes that the loader has done the SMAP call and passed
in the SMAP.  The i386 kernel actually does the SMAP call on its own as well
as some older fallback BIOS calls.

>  HTH
>
>  Eamon Roque
>
>  > So the SMAP problem is that in the one BIOS I looked at, the SMAP BIOS
>  > call
>  > only works from real mode.  Even if invoked from virtual 86 mode, the
>  > BIOS call fails.  FreeBSD only calls the BIOS SMAP call from virtual 86
>  > mode both
>  > in the loader and in the i386 kernel.  The fix is quite complicated and
>  > involves rewriting the boot code to invoke BIOS calls from real mode
>  > rather
>  > than virtual 86 mode.
>  >
>  > --
>  > John Baldwin
>
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-- 
John Baldwin