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

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Message-ID: <54ECFDCF.8040902@nexus-software.ie>
Date:	Tue, 24 Feb 2015 22:40:15 +0000
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	Pavel Machek <pavel@....cz>
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 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.
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