From: Alan Cox <gnomes-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
To: Mathieu Desnoyers
<mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Cc: "Paul E. McKenney"
<paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>,
Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>,
Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>,
Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>,
Chris Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>,
Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
Linus Torvalds
<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>,
Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [RFC PATCH for 4.15 09/14] Provide cpu_opv system call
Date: Fri, 13 Oct 2017 14:57:10 +0100 [thread overview]
Message-ID: <20171013145710.4430583f@alans-desktop> (raw)
In-Reply-To: <20171012230326.19984-10-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
> A maximum limit of 16 operations per cpu_opv syscall invocation is
> enforced, so user-space cannot generate a too long preempt-off critical
> section.
Except that all the operations could be going to mmapped I/O space and if
I pick the right targets could take quite a long time to complete. It's
still only 16 operations - But 160ms is a lot worse than 10ms. In fact
with compare_iter I could make it much much worse still as I get 2 x
TMP_BUFLEN x 16 x worst case latency in my attack. That's enough to screw
up plenty of things.
So it seems to me at minimum it needs to be restricted to genuine RAM user
pages, and in fact would be far far simpler code as well if it were
limited to a single page for a given invocation or if like futexes you
had to specifically create a per_cpu_opv mapping.
Alan
next prev parent reply other threads:[~2017-10-13 13:57 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171012230326.19984-1-mathieu.desnoyers@efficios.com>
2017-10-12 23:03 ` [RFC PATCH v9 for 4.15 01/14] Restartable sequences system call Mathieu Desnoyers
2017-10-13 0:36 ` Linus Torvalds
2017-10-13 9:35 ` Ben Maurer
[not found] ` <DM5PR15MB1690DA99E4AA74FBE54CF7F9CF480-kTBAvIqET4EjX1lkf7hTyId3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-13 18:30 ` Linus Torvalds
[not found] ` <CA+55aFzPBES0JOYuZhuNM7NKN+G9ytZQT2daueFPw0j9HGpdGQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 20:54 ` Paul E. McKenney
[not found] ` <20171013205418.GM3521-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-10-13 21:05 ` Linus Torvalds
[not found] ` <CA+55aFwvNS95ByZJTh1yG25QfaD0K0ZByK3iXeeRU8LafFiGFQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 21:21 ` Paul E. McKenney
2017-10-13 21:36 ` Mathieu Desnoyers
2017-10-16 16:04 ` Carlos O'Donell
2017-10-16 16:46 ` Andi Kleen
2017-10-16 22:17 ` Mathieu Desnoyers
[not found] ` <21865534.42661.1508192263844.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 16:19 ` Ben Maurer
[not found] ` <CY4PR15MB168879D6220D976B04FE482CCF4C0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-17 16:33 ` Mathieu Desnoyers
[not found] ` <1292309161.43101.1508258000235.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 16:41 ` Ben Maurer
[not found] ` <CY4PR15MB16886FD43FB48592F3F5892FCF4C0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-17 17:48 ` Mathieu Desnoyers
2017-10-18 6:22 ` Greg KH
[not found] ` <20171018062226.GB18857-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-10-18 16:28 ` Mathieu Desnoyers
2017-10-14 3:01 ` Andi Kleen
2017-10-14 4:05 ` Linus Torvalds
2017-10-14 11:37 ` Mathieu Desnoyers
2017-10-13 12:50 ` Florian Weimer
2017-10-13 13:40 ` Mathieu Desnoyers
2017-10-13 13:56 ` Florian Weimer
2017-10-13 14:27 ` Mathieu Desnoyers
2017-10-13 17:24 ` Andy Lutomirski
[not found] ` <CALCETrXccCp8apoyUJV8kWLOavnFnenZoU-fbb6cOVZvWp-fnA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-13 17:53 ` Florian Weimer
[not found] ` <3358e696-43e9-15d3-9634-68e9da79e121-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-10-13 18:17 ` Andy Lutomirski
[not found] ` <CALCETrVWZxC=mT9p7HTrAwcAdMzaxwa=A-O0uQt79qy1Cpky_g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-10-14 11:53 ` Mathieu Desnoyers
2017-10-18 16:41 ` Ben Maurer
[not found] ` <CY4PR15MB1688286D6B1283A1C234BAE6CF4E0-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-18 18:11 ` Mathieu Desnoyers
[not found] ` <515879378.43966.1508350299712.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-19 11:35 ` Mathieu Desnoyers
2017-10-19 17:01 ` Florian Weimer
2017-10-23 17:30 ` Ben Maurer
[not found] ` <CY4PR15MB16888F91F41A4A1D322C102CCF460-ZVJ2su15u+xeX4ZvlgGe+Yd3EbNNOtPMvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2017-10-23 20:44 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 02/14] tracing: instrument restartable sequences Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 03/14] Restartable sequences: ARM 32 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 04/14] Restartable sequences: wire up ARM 32 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 05/14] Restartable sequences: x86 32/64 architecture support Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 06/14] Restartable sequences: wire up x86 32/64 system call Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 09/14] Provide cpu_opv " Mathieu Desnoyers
[not found] ` <20171012230326.19984-10-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-13 13:57 ` Alan Cox [this message]
2017-10-13 14:50 ` Mathieu Desnoyers
[not found] ` <854849583.40647.1507906233368.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-14 14:22 ` Mathieu Desnoyers
2017-10-13 17:20 ` Andy Lutomirski
2017-10-14 2:50 ` Andi Kleen
[not found] ` <20171014025029.GL2482-1g7Xle2YJi4/4alezvVtWx2eb7JE58TQ@public.gmane.org>
2017-10-14 13:35 ` Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 10/14] cpu_opv: Wire up x86 32/64 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 12/14] cpu_opv: Wire up ARM32 " Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 13/14] cpu_opv: Implement selftests Mathieu Desnoyers
2017-10-12 23:03 ` [RFC PATCH for 4.15 14/14] Restartable sequences: Provide self-tests Mathieu Desnoyers
2017-10-16 2:51 ` Michael Ellerman
2017-10-16 14:23 ` Mathieu Desnoyers
[not found] ` <399058130.42156.1508163782335.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 10:38 ` Michael Ellerman
2017-10-17 13:50 ` Mathieu Desnoyers
[not found] ` <871sm3n6sy.fsf-W0DJWXSxmBNbyGPkN3NxC2scP1bn1w/D@public.gmane.org>
2017-10-16 18:50 ` Mathieu Desnoyers
[not found] ` <1998166049.42520.1508179805908.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-17 10:36 ` Michael Ellerman
[not found] ` <87d15mjc1g.fsf-W0DJWXSxmBNbyGPkN3NxC2scP1bn1w/D@public.gmane.org>
2017-10-17 13:50 ` Mathieu Desnoyers
[not found] ` <1618170495.42951.1508248216596.JavaMail.zimbra-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-18 5:45 ` Michael Ellerman
[not found] ` <20171012230326.19984-15-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
2017-10-16 3:00 ` Michael Ellerman
2017-10-16 3:48 ` Boqun Feng
2017-10-16 11:48 ` Michael Ellerman
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