linux-kernel - Re: [PATCH] admin-guide/hw-vuln: Rephrase a section of core-scheduling.rst

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Message-ID: <87a6maunzg.fsf@meer.lwn.net>
Date:   Sun, 25 Jul 2021 14:39:47 -0600
From:   Jonathan Corbet <corbet@....net>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Vineeth Pillai <Vineeth.Pillai@...rosoft.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Subject: Re: [PATCH] admin-guide/hw-vuln: Rephrase a section of
 core-scheduling.rst

"Fabio M. De Francesco" <fmdefrancesco@...il.com> writes:

> Rephrase the "For MDS" section in core-scheduling.rst for the purpose of
> making it clearer what is meant by "kernel memory is still considered
> untrusted".
>
> Suggested-by: Vineeth Pillai <Vineeth.Pillai@...rosoft.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  Documentation/admin-guide/hw-vuln/core-scheduling.rst | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/hw-vuln/core-scheduling.rst b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
> index 7b410aef9c5c..e6b5ceb219ec 100644
> --- a/Documentation/admin-guide/hw-vuln/core-scheduling.rst
> +++ b/Documentation/admin-guide/hw-vuln/core-scheduling.rst
> @@ -181,10 +181,11 @@ Open cross-HT issues that core scheduling does not solve
>  --------------------------------------------------------
>  1. For MDS
>  ~~~~~~~~~~
> -Core scheduling cannot protect against MDS attacks between an HT running in
> -user mode and another running in kernel mode. Even though both HTs run tasks
> -which trust each other, kernel memory is still considered untrusted. Such
> -attacks are possible for any combination of sibling CPU modes (host or guest mode).
> +Core scheduling cannot protect against MDS attacks between the siblings running in
> +user mode and the others running in kernel mode. Even though all siblings run tasks
> +which trust each other, when the kernel is executing code on behalf of a task, it
> +cannot trust the code running in the sibling. Such attacks are possible for any
> +combination of sibling CPU modes (host or guest mode).

Applied, thanks.  I took the liberty of reflowing that paragraph to keep
the line lengths reasonable...

jon