linux-kernel - Re: [PATCH] iommu-PMEN

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Message-ID: <20071027001938.GB10215@rhun.ibm.com>
Date:	Sat, 27 Oct 2007 02:19:38 +0200
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Mark Gross <mgross@...ux.intel.com>
Cc:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] iommu-PMEN_REG boot up support

On Fri, Oct 26, 2007 at 11:18:49AM -0700, Mark Gross wrote:

> The following patch clears the portect memory region enable bit at
> boot time by default.  It also provides a kernel parrameter for
> disabling this behavior and leave the PMEN_REG untouched if so
> wanted.
> 
> If the boot loader or platform has protected memory regions enabled
> at boot time it could prevent DMA's from happening as drivers are
> loaded and used.

What's the value of adding a command line option for this? Under what
circumstances would we want to not clear this bit?

> +		} else if (!strncmp(str, "no_epm_clear", 12)) {
> +			printk(KERN_INFO
> +				"Intel-IOMMU: subress clearing of Enable "
> +				"Protected Memory bit\n");
> +			clear_pmen_epm = 0;

`suppress', I assume. Rest looks fine, if the configuration option is
really needed.

Cheers,
Muli
-- 
SYSTOR 2007 --- 1st Annual Haifa Systems and Storage Conference 2007
http://www.haifa.il.ibm.com/Workshops/systor2007/

Virtualization workshop: Oct 29th, 2007 | Storage workshop: Oct 30th, 2007
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