From: Peter Zijlstra <peterz@infradead.org>
To: Prarit Bhargava <prarit@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>,
x86@kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH] x86/fpu: Parse comma separated list passed in clearcpuid
Date: Thu, 21 Feb 2019 14:37:45 +0100 [thread overview]
Message-ID: <20190221133745.GP32494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190221131225.22063-1-prarit@redhat.com>
On Thu, Feb 21, 2019 at 08:12:25AM -0500, Prarit Bhargava wrote:
> Users cannot disable multiple CPU features with the kernel parameter
> clearcpuid=. For example, "clearcpuid=154 clearcpuid=227" only disables
> CPUID bit 154.
>
> Previous to commit 0c2a3913d6f5 ("x86/fpu: Parse clearcpuid= as early XSAVE
> argument") it was possible to pass multiple clearcpuid options as kernel
> parameters using individual entries. With the new code it isn't easy to
> replicate exactly that behaviour but a comma separated list can be easily
> implemented, eg) "clearcpuid=154,227"
>
> Make the clearcpuid parse a comma-separated list of values instead of only
> a single value.
So I think the feature is broken as is; because it doesn't clear the
CPUID bits for userspace.
something along the lines of:
https://lkml.kernel.org/r/20190212164833.GK32494@hirez.programming.kicks-ass.net
would be required to make it so.
next prev parent reply other threads:[~2019-02-21 13:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-21 13:12 [PATCH] x86/fpu: Parse comma separated list passed in clearcpuid Prarit Bhargava
2019-02-21 13:37 ` Peter Zijlstra [this message]
2019-02-21 18:58 ` Andi Kleen
2019-02-21 19:01 ` Prarit Bhargava
2019-02-21 13:48 ` Peter Zijlstra
2019-02-27 23:48 ` Prarit Bhargava
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