linux-kernel - RE: [PATCH] cpu/bugs: Disable CPU mitigations at compilation time

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Message-ID: <bdcc00582da6454ab7e5778ad108a1d7@AcuMS.aculab.com>
Date:   Mon, 12 Jun 2023 12:16:19 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Borislav Petkov' <bp@...en8.de>
CC:     Breno Leitao <leitao@...ian.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "pawan.kumar.gupta@...ux.intel.com" 
        <pawan.kumar.gupta@...ux.intel.com>,
        "paul@...l-moore.com" <paul@...l-moore.com>,
        "leit@...a.com" <leit@...a.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] cpu/bugs: Disable CPU mitigations at compilation time

From: Borislav Petkov
> Sent: 12 June 2023 12:52
> 
> On Mon, Jun 12, 2023 at 11:22:15AM +0000, David Laight wrote:
> > I can definitely justify compiling them all out.
> > For instance embedded systems with limited userspace and
> > (pretty much) everything running as root.
> 
> Nothing's stopping you from adding "mitigations=off" to your grub
> config.

I do (and I compile without page table separation),
but some of the run-time patched versions are not as 'good'
as compiling the code out.
It might just be some nops, but maybe it is worse.
This can be particularly true for new mitigations.

	David

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