linux-kernel - Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi machine

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Message-ID: <506BCEAB.4090204@zytor.com>
Date:	Tue, 02 Oct 2012 22:35:39 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <mjg@...hat.com>
CC:	Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@...com>,
	T Makphaibulchoke <tmac@...com>, tglx@...utronix.de,
	mingo@...hat.com, x86@...nel.org, akpm@...ux-foundation.org,
	yinghai@...nel.org, tiwai@...e.de, viro@...iv.linux.org.uk,
	aarcange@...hat.com, tony.luck@...el.com, mgorman@...e.de,
	weiyang@...ux.vnet.ibm.com, octavian.purdila@...el.com,
	paul.gortmaker@...driver.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] Fix devmem_is_allowed for below 1MB accesses for an efi
 machine

On 10/02/2012 10:28 PM, Matthew Garrett wrote:
> On Tue, Oct 02, 2012 at 11:13:17PM -0600, Thavatchai Makphaibulchoke wrote:
> 
>> Sounds like a better solution is to allow accesses to only I/O regions 
>> presented in the EFI memory map for physical addresses below 1 MB.
> 
> That won't work - unfortunately we do still need the low region to be 
> available for X because some platforms expect us to use int10 even on 
> EFI (yes, yes, I know). Do you have a copy of the EFI memory map for a 
> system that's broken with the current code?
> 

I honestly think this calls for a quirk, or more likely, no action at
all ("don't do that, then.")

	-hpa


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