linux-kernel - Re: [RFC v5][PATCH 2/4] intel_txt: Intel(R) TXT reboot/halt shutdown support

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Message-ID: <20090624150453.GJ1784@ucw.cz>
Date:	Wed, 24 Jun 2009 17:04:53 +0200
From:	Pavel Machek <pavel@....cz>
To:	Joseph Cihula <joseph.cihula@...el.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, arjan@...ux.intel.com,
	hpa@...or.com, andi@...stfloor.org, chrisw@...s-sol.org,
	jmorris@...ei.org, jbeulich@...ell.com, peterm@...hat.com,
	gang.wei@...el.com, shane.wang@...el.com
Subject: Re: [RFC v5][PATCH 2/4] intel_txt: Intel(R) TXT reboot/halt
	shutdown support

On Mon 2009-06-22 17:41:34, Joseph Cihula wrote:
> Support for graceful handling of kernel reboots after an Intel(R) TXT launch.
> 
> Without this patch, attempting to reboot or halt the system will cause the
> TXT hardware to lock memory upon system restart because the secrets-in-memory
> flag that was set on launch was never cleared.  This will in turn cause BIOS
> to execute a TXT Authenticated Code Module (ACM) that will scrub all of memory
> and then unlock it.  Depending on the amount of memory in the system and its type,
> this may take some time.
> 
> This patch creates a 1:1 address mapping to the tboot module and then calls back
> into tboot so that it may properly and securely clean up system state and clear
> the secrets-in-memory flag.  When it has completed these steps, the tboot module
> will reboot or halt the system.

Is it faster to clean memory from OS as opposed to bios doing the
clearing? If so, why?
								Pavel

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