Subject: Re: [PATCH 11/18] Hibernate: introduced RSA key-pair to verify
 signature of snapshot
From: joeyli <jlee@suse.com>
To: Matt Fleming <matt@console-pimps.org>
Cc: linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org,
        linux-efi@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-crypto@vger.kernel.org, opensuse-kernel@opensuse.org,
        David Howells <dhowells@redhat.com>, "Rafael J. Wysocki" <rjw@sisk.pl>,
        Matthew Garrett <mjg59@srcf.ucam.org>, Len Brown <len.brown@intel.com>,
        Pavel Machek <pavel@ucw.cz>, Josh Boyer <jwboyer@redhat.com>,
        Vojtech Pavlik <vojtech@suse.cz>,
        Matt Fleming <matt.fleming@intel.com>,
        James Bottomley <james.bottomley@hansenpartnership.com>,
        Greg KH <gregkh@linuxfoundation.org>, JKosina@suse.com,
        Rusty Russell <rusty@rustcorp.com.au>,
        Herbert Xu <herbert@gondor.hengli.com.au>,
        "David S. Miller" <davem@davemloft.net>,
        "H. Peter Anvin" <hpa@zytor.com>, Michal Marek <mmarek@suse.cz>,
        Gary Lin <GLin@suse.com>, Vivek Goyal <vgoyal@redhat.com>,
        Takashi Iwai <tiwai@suse.de>
In-Reply-To: <20130905103158.GM28598@console-pimps.org>
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Date: Thu, 05 Sep 2013 21:28:57 +0800
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於 四，2013-09-05 於 11:31 +0100，Matt Fleming 提到：
> On Thu, 05 Sep, at 06:13:36PM, joeyli wrote:
> > This S4WakeKey is a VOLATILE variable that could not modify by
> > SetVariable() at runtime. So, it's read only even through efivars. 
> > 
> > Does it what your concern?
>  
> No, the UEFI spec probibits certain runtime functions from being
> executed concurrently on separate cpus and the spinlock used in the
> efivars code ensures that we adhere to that restriction. See table 31 in
> section 7.1 of the UEFI 2.4 spec for the list of services that are
> non-reentrant.
> 
> The problem isn't that we want to avoid simultaneous access to
> S4WakeKey, it's that we can't invoke any of the variable runtime service
> functions concurrently.
> 

I see! I will use efivar api to access EFI variable.

Thanks a lot!
Joey Lee

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