From: Andrea Arcangeli <aarcange@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Dave Hansen <dave.hansen@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jiri Kosina <jikos@kernel.org>,
"asit.k.mallick" <asit.k.mallick@intel.com>,
"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linuxfoundation.org>,
x86@kernel.org, Borislav Petkov <bp@alien8.de>,
Tim Chen <tim.c.chen@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [patch RFC 5/5] x86/speculation: Add basic speculation control code
Date: Wed, 10 Jan 2018 16:47:29 +0100 [thread overview]
Message-ID: <20180110154729.GK9417@redhat.com> (raw)
In-Reply-To: <1515597857.22302.190.camel@infradead.org>
On Wed, Jan 10, 2018 at 03:24:17PM +0000, David Woodhouse wrote:
> Since it achieves nothing¹ but to make userspace run slower, there's no
> need to write it again on returning to userspace. It will perform that
> function just fine without doing so.
Ok, very glad we are on the same page now.
Note that as far as I can tell there was no way to answer the above
question by reading the spec.
You also explicitly used the word barrier in association with IBRS
before, but there was no word barrier in the aforementioned specs in
association with IBRS (every word barrier was always and only in
association with IBPB).
I hope this discussion helped clear the additional barrier semantics
of IBRS in more understandable way for the current/future upstream
code.
Thanks,
Andrea
next prev parent reply other threads:[~2018-01-10 15:47 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-10 1:06 [patch RFC 0/5] x86/spectre_v2: Initial integration of IBRS into the spectre_v2 mechanics Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 1/5] x86/CPU: Sync CPU feature flags late Thomas Gleixner
2018-01-10 1:37 ` Dave Hansen
2018-01-10 1:39 ` Van De Ven, Arjan
2018-01-10 1:47 ` Thomas Gleixner
2018-01-10 2:57 ` Andy Lutomirski
2018-01-10 11:02 ` Thomas Gleixner
2018-01-10 1:44 ` Thomas Gleixner
2018-01-10 6:20 ` Ingo Molnar
2018-01-10 11:33 ` Borislav Petkov
2018-01-10 12:38 ` Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 2/5] x86/spectre: Simplify spectre code a bit Thomas Gleixner
2018-01-10 6:22 ` Ingo Molnar
2018-01-10 1:06 ` [patch RFC 3/5] x86/spectre: Prepare for IBRS selection Thomas Gleixner
2018-01-10 1:51 ` Dave Hansen
2018-01-10 1:06 ` [patch RFC 4/5] x86/cpufeatures: Detect Speculation control feature Thomas Gleixner
2018-01-10 6:32 ` Ingo Molnar
2018-01-10 11:06 ` Thomas Gleixner
2018-01-10 1:06 ` [patch RFC 5/5] x86/speculation: Add basic speculation control code Thomas Gleixner
2018-01-10 2:02 ` Dave Hansen
2018-01-10 4:11 ` Justin Forbes
2018-01-10 9:22 ` Peter Zijlstra
2018-01-10 9:27 ` David Woodhouse
2018-01-10 10:03 ` Peter Zijlstra
2018-01-10 11:22 ` David Woodhouse
2018-01-10 11:41 ` Thomas Gleixner
2018-01-10 11:45 ` Peter Zijlstra
2018-01-10 11:54 ` Andrea Arcangeli
2018-01-10 11:58 ` David Woodhouse
2018-01-10 12:01 ` Andrea Arcangeli
2018-01-10 12:07 ` Andrea Arcangeli
2018-01-10 12:12 ` David Woodhouse
2018-01-10 12:20 ` Andrea Arcangeli
2018-01-10 12:27 ` Andrea Arcangeli
2018-01-10 13:42 ` Van De Ven, Arjan
2018-01-10 12:09 ` David Woodhouse
2018-01-10 12:17 ` Andrea Arcangeli
2018-01-10 12:29 ` David Woodhouse
2018-01-10 12:41 ` Andrea Arcangeli
2018-01-10 12:47 ` Jiri Kosina
2018-01-10 12:51 ` David Woodhouse
2018-01-10 13:02 ` Andrea Arcangeli
2018-01-10 13:05 ` Andrea Arcangeli
2018-01-10 13:10 ` Andrea Arcangeli
2018-01-10 13:12 ` Andrea Arcangeli
2018-01-10 12:57 ` Andrea Arcangeli
2018-01-10 13:07 ` David Woodhouse
2018-01-10 13:45 ` Van De Ven, Arjan
2018-01-10 13:52 ` Andrea Arcangeli
2018-01-10 13:53 ` Van De Ven, Arjan
2018-01-10 21:35 ` Tim Chen
2018-01-10 22:13 ` Andrea Arcangeli
2018-01-10 13:46 ` Thomas Gleixner
2018-01-10 13:51 ` Van De Ven, Arjan
2018-01-10 13:53 ` Thomas Gleixner
2018-01-10 13:58 ` David Woodhouse
2018-01-10 14:10 ` Andrea Arcangeli
2018-01-10 14:14 ` Van De Ven, Arjan
2018-01-10 14:59 ` Dave Hansen
2018-01-10 15:13 ` Andrea Arcangeli
2018-01-10 15:24 ` David Woodhouse
2018-01-10 15:47 ` Andrea Arcangeli [this message]
2018-01-10 15:56 ` David Woodhouse
2018-01-10 13:10 ` Jiri Kosina
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