linux-kernel - Re: [PATCH v3 1/1] x86: Add Isolated Memory Regions for Quark X1000

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Message-ID: <20150302121919.GD27317@amd>
Date:	Mon, 2 Mar 2015 13:19:19 +0100
From:	Pavel Machek <pavel@....cz>
To:	Bryan O'Donoghue <pure.logic@...us-software.ie>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, dvhart@...radead.org, andy.shevchenko@...il.com,
	boon.leong.ong@...el.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] x86: Add Isolated Memory Regions for Quark X1000

On Tue 2015-02-24 22:40:15, Bryan O'Donoghue wrote:
> On 23/02/15 22:18, Pavel Machek wrote:
> >On Mon 2015-01-26 14:15:27, Bryan O'Donoghue wrote:
> 
> >
> >Do the applications normally need to manipulate IMRs?
> 
> 
> Applications could in theory manipulate IMRs - you might want to place an
> IMR around an EFI capsule in memory for example - before calling a capsule
> update.
> 
> This code will place an IMR around the kernel .text - .rodata which ensures
> that no unwarranted DMA access can rewrite write-only kernel addresses -
> something the MMU would not fault on - on non-IMR enabled processors.
> 
> >Would it be
> >possible to do all IMR manipulations in the bootloader?
> >
> 
> Possible yes - in practical terms for Galileo or the SMARC+Quark from
> Kontron for example - you'd be forcing a bootloader change - which most
> users will not pick up.
> 
> 
> Considering IMRs can reset the system if they aren't sanitized, it's good
> practice for the kernel to go and make sure that every unlocked IMR is
> torn-down and reset.

Ok, makes sense.
										Pavel
-- 
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