From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
Ben Maurer <bmaurer@fb.com>, rostedt <rostedt@goodmis.org>,
Josh Triplett <josh@joshtriplett.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>, Michael Kerrisk <mtk.ma>
Subject: Re: [RFC PATCH for 4.18 3/5] rseq: uapi: declare rseq_cs field as union, update includes
Date: Fri, 6 Jul 2018 15:35:41 -0400 (EDT) [thread overview]
Message-ID: <1913049637.1366.1530905741745.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <CA+55aFzz1CC6son0T2nD-Yqhy0_yC5nBer2XSH9kqe5x3N26Ug@mail.gmail.com>
----- On Jul 6, 2018, at 3:31 PM, Linus Torvalds torvalds@linux-foundation.org wrote:
> On Fri, Jul 6, 2018 at 12:23 PM Mathieu Desnoyers
> <mathieu.desnoyers@efficios.com> wrote:
>>
>> For -rc, I would favor the following simpler approach. Or I could even
>> just use get_user() instead. Thoughts ?
>
> Please just use "get_user()".
>
> In fact, we should be thinking seriosly about just removing
> __get_user() entirely. It's wrong. It optimizes the wrong thing
> entirely. It _used_ to be that the range check was noticeable, and it
> really isn't any more. These days the expensive parts are the SMAP
> costs, and both get_user() and __get_user() have those, except
> get_user() is safer and doesn't waste I$ on inlining the code to
> disable and re-enable SMAP.
Will do, thanks!
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
WARNING: multiple messages have this Message-ID (diff)
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
Ben Maurer <bmaurer@fb.com>, rostedt <rostedt@goodmis.org>,
Josh Triplett <josh@joshtriplett.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Joel Fernandes <joelaf@google.com>
Subject: Re: [RFC PATCH for 4.18 3/5] rseq: uapi: declare rseq_cs field as union, update includes
Date: Fri, 6 Jul 2018 15:35:41 -0400 (EDT) [thread overview]
Message-ID: <1913049637.1366.1530905741745.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <CA+55aFzz1CC6son0T2nD-Yqhy0_yC5nBer2XSH9kqe5x3N26Ug@mail.gmail.com>
----- On Jul 6, 2018, at 3:31 PM, Linus Torvalds torvalds@linux-foundation.org wrote:
> On Fri, Jul 6, 2018 at 12:23 PM Mathieu Desnoyers
> <mathieu.desnoyers@efficios.com> wrote:
>>
>> For -rc, I would favor the following simpler approach. Or I could even
>> just use get_user() instead. Thoughts ?
>
> Please just use "get_user()".
>
> In fact, we should be thinking seriosly about just removing
> __get_user() entirely. It's wrong. It optimizes the wrong thing
> entirely. It _used_ to be that the range check was noticeable, and it
> really isn't any more. These days the expensive parts are the SMAP
> costs, and both get_user() and __get_user() have those, except
> get_user() is safer and doesn't waste I$ on inlining the code to
> disable and re-enable SMAP.
Will do, thanks!
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-07-06 19:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-05 18:05 [RFC PATCH for 4.18 0/5] Restartable Sequences updates Mathieu Desnoyers
2018-07-05 18:05 ` Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 1/5] rseq: use __u64 for rseq_cs fields, validate user inputs Mathieu Desnoyers
2018-07-05 18:05 ` Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 2/5] rseq: uapi: update uapi comments Mathieu Desnoyers
2018-07-05 18:05 ` Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 3/5] rseq: uapi: declare rseq_cs field as union, update includes Mathieu Desnoyers
2018-07-05 18:05 ` Mathieu Desnoyers
2018-07-06 16:02 ` Mathieu Desnoyers
2018-07-06 16:02 ` Mathieu Desnoyers
2018-07-06 19:23 ` Mathieu Desnoyers
2018-07-06 19:23 ` Mathieu Desnoyers
2018-07-06 19:31 ` Linus Torvalds
2018-07-06 19:31 ` Linus Torvalds
2018-07-06 19:35 ` Mathieu Desnoyers [this message]
2018-07-06 19:35 ` Mathieu Desnoyers
2018-07-06 19:38 ` Mathieu Desnoyers
2018-07-06 19:38 ` Mathieu Desnoyers
2018-07-06 19:56 ` Linus Torvalds
2018-07-06 19:56 ` Linus Torvalds
2018-07-07 15:06 ` Russell King - ARM Linux
2018-07-07 15:06 ` Russell King - ARM Linux
2018-07-06 19:56 ` Andy Lutomirski
2018-07-06 19:56 ` Andy Lutomirski
2018-07-05 18:06 ` [RFC PATCH for 4.18 4/5] rseq: remove unused types_32_64.h uapi header Mathieu Desnoyers
2018-07-05 18:06 ` Mathieu Desnoyers
2018-07-05 18:06 ` [RFC PATCH for 4.18 5/5] rseq/selftests: cleanup: update comment above rseq_prepare_unload Mathieu Desnoyers
2018-07-05 18:06 ` Mathieu Desnoyers
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