From: joeyli <jlee@suse.com>
Subject: Re: [PATCH 11/18] Hibernate: introduced RSA key-pair to verify
 signature of snapshot
Date: Thu, 05 Sep 2013 21:28:57 +0800
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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,
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	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.apana.org.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>
To: Matt Fleming <matt@console-pimps.org>
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=E6=96=BC =E5=9B=9B=EF=BC=8C2013-09-05 =E6=96=BC 11:31 +0100=EF=BC=8CMa=
tt Fleming =E6=8F=90=E5=88=B0=EF=BC=9A
> 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.=20
> >=20
> > Does it what your concern?
> =20
> 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.
>=20
> 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 serv=
ice
> functions concurrently.
>=20

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

Thanks a lot!
Joey Lee