linux-kernel - Re: [PATCH 0/2] efivars: reading variables can generate SMIs

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Message-ID: <20180216185856.GE29042@pd.tnic>
Date:   Fri, 16 Feb 2018 19:58:56 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joe Konno <joe.konno@...ux.intel.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>, linux-efi@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jeremy Kerr <jk@...abs.org>, Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Benjamin Drung <benjamin.drung@...fitbricks.com>,
        Peter Jones <pjones@...hat.com>
Subject: Re: [PATCH 0/2] efivars: reading variables can generate SMIs

On Fri, Feb 16, 2018 at 10:48:32AM -0800, Joe Konno wrote:
>  We may see some other patches or RFCs about caching and/or shadowing
> variable values in efivarfs to reduce the number of direct EFI reads,
> with the goal of reducing how many SMIs are generated.

So if you do the caching scheme, the question about narrowing
permissions becomes moot...

> Any obvious EFI variables that userspace tools have come to depend on--
> those which normal, unprivileged users need to read-- are helpful inputs
> to this discussion.

... which solves the aspect of not breaking userspace nicely.

-- 
Regards/Gruss,
    Boris.

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