Re: kernel goes dark on boot

[tlaronde%polynum.com@localhost]

Le Tue, Feb 21, 2023 at 10:00:10AM -0400, Jared McNeill a écrit :
> Yeah sorry you can?t just not exit boot services and boot the OS. UEFI code has certain expectations around the execution environment (MMU on, 1:1 PA to VA for example) that starting the kernel is going to interfere with. The moment the kernel touches the MMU, all of the resident UEFI code will cease to function. This includes code that may be running asynchronously (timers etc) that are not stopped properly due to the missing ExitBootServices call.
> 

FWIW, having followed EDK II development list for a while, there are
further modifications at the moment made because a lot of people are
focusing on VMs (there is quite a market on this) and want to use
EDK II UEFI code as emulated BIOS. And it must be noted that qemu seems
to be the main target.

Just a caveats for the braves who want to follow this...

T. Laronde

> 
> > On Feb 21, 2023, at 9:46 AM, Emmanuel Dreyfus <manu%netbsd.org@localhost> wrote:
> > 
> > ?On Tue, Feb 21, 2023 at 08:05:00AM -0400, Jared McNeill wrote:
> >> After calling ExitBootServices(), the only things that work are UEFI runtime
> >> services. You'll have to find another way to print to the console.
> > 
> > I can skip the ExitBootServices call and keep printing, I have already
> > done thatn at least in C functions. I have no experience of doing that
> > from assembly code.
> > 
> > The same bug exists with a XEN3_DOM0 kernel. Xen starts up, and the 
> > kernel crash without displaying anything. I wonder if there are tools
> > to trace the dom0 with help from Xen.
> > 
> > -- 
> > Emmanuel Dreyfus
> > manu%netbsd.org@localhost
> 

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        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
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