Re: [PATCH 0/4] EFI 1:1 mapping

[James Bottomley <James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org>]

On Mon, 2013-06-03 at 19:11 +0100, Matthew Garrett wrote:
> > > The problem there is that you're saying "In theory". We know that 
> > > Windows doesn't behave this way, so we have no legitimate expectation 
> > > that it'll work. We know that it doesn't on some Apple hardware.
> > 
> > Fine, you say we need to call SetVirtualAddressMap because windows does,
> > I agree, I'm just saying we get additional safety from calling it with
> > the 1:1 map ... I don't see what the problem is.
> 
> No. I'm saying that calling it with the 1:1 map is something very 
> different to the behaviour of Windows, and I'm saying that doing so is 
> known to cause variable writes on some Apple hardware to stop working. 
> If we're aiming for maximum compatibility, we need to call 
> SetVirtualAddressMap() with addresses above the canonicalisation hole.

OK, so tell me this problem: it's a new one one me.  I think you're
saying if we don't call SetVirtualAddressMap with a mapping above a
certain value, some Apple system breaks somehow? (how?).

James