From: Andi Kleen <andi@firstfloor.org>
To: Keno Fischer <keno@juliacomputing.com>
Cc: linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andi Kleen <andi@firstfloor.org>, Kyle Huey <khuey@kylehuey.com>,
Robert O'Callahan <robert@ocallahan.org>
Subject: Re: [RFC PATCH v2] x86/arch_prctl: Add ARCH_SET_XCR0 to set XCR0 per-thread
Date: Tue, 7 Apr 2020 07:20:03 -0700 [thread overview]
Message-ID: <20200407142002.jxzc3xcuyoznjgkh@two.firstfloor.org> (raw)
In-Reply-To: <20200407011259.GA72735@juliacomputing.com>
> Thank you in advance for any review comments - I thought the comments
> on v1 were quite helpful. I understand this is a tall ask for mainline
> inclusion, but the feature is just too useful for me to give up ;).
> [1] https://lkml.org/lkml/2018/6/16/134
The rationale from that post should have been in this description.
You can already do what you want using the clearcpuid= boot flags using the
infrastructure in [1], which is in newer kernels.
So to disable AVX512 you would use clearcpuid=304 and the AVX feature
set should be the same as Haswell. To disable AVX2 you would use
clearcpuid=293 and you get the same feature set as Sandy Bridge.
A boot option is not as convenient as a run time setting, but has a lot
less weird corner cases.
-Andi
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/x86/kernel/cpu/cpuid-deps.c?id=0b00de857a648dafe7020878c7a27cf776f5edf4
-Andi
next prev parent reply other threads:[~2020-04-07 14:20 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 1:12 [RFC PATCH v2] x86/arch_prctl: Add ARCH_SET_XCR0 to set XCR0 per-thread Keno Fischer
2020-04-07 3:57 ` Andy Lutomirski
2020-04-07 4:44 ` Keno Fischer
2020-04-07 4:53 ` Kyle Huey
2020-04-07 12:33 ` Peter Zijlstra
2020-04-07 13:52 ` Keno Fischer
2020-04-07 12:21 ` Peter Zijlstra
2020-04-07 14:06 ` Dave Hansen
2020-04-07 14:16 ` Andy Lutomirski
2020-04-07 18:30 ` Keno Fischer
2020-04-14 23:20 ` Andy Lutomirski
2020-04-15 0:09 ` Keno Fischer
2020-04-16 1:07 ` Andy Lutomirski
2020-04-16 1:14 ` Keno Fischer
2020-04-16 1:16 ` Keno Fischer
2020-04-16 1:22 ` Andy Lutomirski
2020-04-07 16:29 ` Kyle Huey
2020-04-07 13:14 ` Dave Hansen
[not found] ` <CABV8kRw1TQsqs+z43bSfZ5isctuFGMB4g_ztDYihiiXHcy4nVA@mail.gmail.com>
2020-04-07 16:27 ` Dave Hansen
2020-04-07 17:55 ` Keno Fischer
2020-04-07 20:21 ` Dave Hansen
2020-04-07 21:42 ` Andy Lutomirski
2020-04-07 22:15 ` Keno Fischer
2020-04-14 19:55 ` Keno Fischer
2020-04-07 14:20 ` Andi Kleen [this message]
2020-04-07 18:06 ` Keno Fischer
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