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Date: Mon, 19 Mar 2012 12:02:21 -0400
From: Shea Levy <shea@shealevy.com>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Matt Fleming <matt.fleming@intel.com>, "H. Peter Anvin" <hpa@zytor.com>,
        linux-kernel@vger.kernel.org
Subject: Re: EFI Boot Stub Early Console
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On 3/19/12 11:56 AM, Alan Cox wrote:
>>> any bootloader (including the bootstub) will call ExitBootServices()
>>> before any printk'ing actually happens?? Or am I misunderstanding the
>>> spec somehow? I suppose I could just try it and see what happens...
>> Oops. Good point, that isn't going to work.
> Surely it works fine if you are using bootstub directly from EFI ?

ConOut will work before the call to ExitBootServices(), but any 
bootloader (including the boot stub) calls that before starting the 
normal kernel boot process. I'm working on a generic earlyprintk that 
provides the same functionality as the existing earlyprintks that will 
work for any EFI boot. Matt already submitted a patch for an efi_printk 
that will be sufficient for the boot stub itself before the call to 
ExitBootServices().

~Shea