From: joeyli <jlee-IBi9RG/b67k@public.gmane.org>
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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To: Matt Fleming <matt-HNK1S37rvNbeXh+fF434Mdi2O/JbrIOy@public.gmane.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