linux-kernel - Re: [PATCH 1/4] Documentation: arm: [U]EFI runtime services

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Message-ID: <20130627090050.GC18151@rocoto.smurfnet.nu>
Date:	Thu, 27 Jun 2013 11:00:50 +0200
From:	Leif Lindholm <leif.lindholm@...aro.org>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Matt Fleming <matt@...sole-pimps.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-efi@...r.kernel.org,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"patches@...aro.org" <patches@...aro.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>, matt.fleming@...el.com
Subject: Re: [PATCH 1/4] Documentation: arm: [U]EFI runtime services

On Thu, Jun 27, 2013 at 02:32:19AM +0100, Matthew Garrett wrote:
> On Wed, Jun 26, 2013 at 07:38:19AM -0700, James Bottomley wrote:
> > The fixed virtual address scheme currently being looked at for x86_64 to
> > make SetVirtualAddressMap() kexec invariant doesn't work on 32 bit
> > because the address space isn't big enough.  For ARM, given that we've
> > much more opportunity to work with the vendors, can we just avoid
> > transitioning to a virtual address map and always just install a
> > physical mapping before doing efi calls?
> 
> We can probably get away with that now, but it does risk us ending up 
> with some firmware that expects to run in physical mode (boards designed 
> for Linux) and some firmware that expects to run in virtual mode (boards 
> designed for Windows). The degree of lockdown in the Windows ecosystem 
> at present means it's not a real problem at the moment, but if that ever 
> changes we're going to risk incompatibility.

Is there anything preventing calling SetVirtualAddressMap() with a
1:1 map?

Or do you simply mean that some platforms might cruise along with
undetected bugs in their relocation hooks?

/
    Leif
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