linux-kernel - Re: [PATCH 5/7] x86: Use IBRS for firmware update path

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Message-ID: <20180104184845.7a40525a@alans-desktop>
Date:   Thu, 4 Jan 2018 18:48:45 +0000
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        linux-kernel@...r.kernel.org, David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH 5/7] x86: Use IBRS for firmware update path

On Thu,  4 Jan 2018 09:56:46 -0800
Tim Chen <tim.c.chen@...ux.intel.com> wrote:

> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> We are impervious to the indirect branch prediction attack with retpoline
> but firmware won't be, so we still need to set IBRS to protect
> firmware code execution when calling into firmware at runtime.

If you are going to care about APM then you also need to care about
BIOS32 interfaces (arch/x86/pc/pcibios.c) and PNPBIOS
(drivers/pnp/pnpbios/bioscalls.c)

Alan