From: Borislav Petkov <bp@alien8.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>,
Andy Lutomirski <luto@amacapital.net>,
Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Denys Vlasenko <vda.linux@googlemail.com>,
Brian Gerst <brgerst@gmail.com>, Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Alexei Starovoitov <ast@plumgrid.com>,
Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue
Date: Mon, 27 Apr 2015 20:47:30 +0200 [thread overview]
Message-ID: <20150427184730.GH28871@pd.tnic> (raw)
In-Reply-To: <CA+55aFx0Z++eowxUod_NGov88hPne+BJSRc+=NgTsHCqyG00+A@mail.gmail.com>
On Mon, Apr 27, 2015 at 11:12:05AM -0700, Linus Torvalds wrote:
> So if one or two cycles in this code doesn't matter, then why are we
> adding alternate instructions just to avoid a few ALU instructions and
> a conditional branch that predicts perfectly? And if it does matter,
> then the 6-byte option looks clearly better..
You know what? I haven't even measured the tree *without* Denys'
stricter RCX canonical-ness patch. All numbers so far are from 4.0+ with
tip/master ontop which has Denys' patch.
And I *should* measure once with plain 4.1-rc1 and then with Denys'
patch ontop to see whether this all jumping-thru-alternatives-hoops is
even worth it.
If nothing else, it was a nice exercise. :-)
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
next prev parent reply other threads:[~2015-04-27 18:47 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-24 2:15 Andy Lutomirski
2015-04-24 2:18 ` Andy Lutomirski
2015-04-26 12:34 ` Denys Vlasenko
2015-04-24 3:58 ` Brian Gerst
2015-04-24 9:59 ` Denys Vlasenko
2015-04-24 10:59 ` Borislav Petkov
2015-04-24 19:58 ` Borislav Petkov
2015-04-24 11:27 ` Denys Vlasenko
2015-04-24 12:00 ` Brian Gerst
2015-04-24 16:25 ` Linus Torvalds
2015-04-24 17:33 ` Brian Gerst
2015-04-24 17:41 ` Linus Torvalds
2015-04-24 17:57 ` Brian Gerst
2015-04-24 20:21 ` Andy Lutomirski
2015-04-24 20:46 ` Denys Vlasenko
2015-04-24 20:50 ` Andy Lutomirski
2015-04-24 21:45 ` H. Peter Anvin
2015-04-24 21:45 ` H. Peter Anvin
2015-04-24 21:45 ` H. Peter Anvin
2015-04-24 21:45 ` H. Peter Anvin
2015-04-24 21:45 ` H. Peter Anvin
2015-04-24 21:45 ` H. Peter Anvin
2015-04-25 2:17 ` Denys Vlasenko
2015-04-26 23:36 ` Andy Lutomirski
2015-04-24 20:53 ` Linus Torvalds
2015-04-25 21:12 ` Borislav Petkov
2015-04-26 11:22 ` perf numbers (was: Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue) Borislav Petkov
2015-04-26 23:39 ` [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue Andy Lutomirski
2015-04-27 8:53 ` Borislav Petkov
2015-04-27 10:07 ` Denys Vlasenko
2015-04-27 10:09 ` Borislav Petkov
2015-04-27 11:35 ` Borislav Petkov
2015-04-27 12:08 ` Denys Vlasenko
2015-04-27 12:48 ` Borislav Petkov
2015-04-27 14:57 ` Linus Torvalds
2015-04-27 15:06 ` Linus Torvalds
2015-04-27 15:35 ` Borislav Petkov
2015-04-27 15:46 ` Borislav Petkov
2015-04-27 15:56 ` Andy Lutomirski
2015-04-27 16:04 ` Brian Gerst
2015-04-27 16:10 ` Denys Vlasenko
2015-04-27 16:00 ` Linus Torvalds
2015-04-27 16:40 ` Borislav Petkov
2015-04-27 18:14 ` Linus Torvalds
2015-04-27 18:38 ` Borislav Petkov
2015-04-27 18:47 ` Linus Torvalds
2015-04-27 18:53 ` Borislav Petkov
2015-04-27 19:59 ` H. Peter Anvin
2015-04-27 20:03 ` Borislav Petkov
2015-04-27 20:14 ` H. Peter Anvin
2015-04-28 15:55 ` Borislav Petkov
2015-04-28 16:28 ` Linus Torvalds
2015-04-28 16:58 ` Borislav Petkov
2015-04-28 17:16 ` Linus Torvalds
2015-04-28 18:38 ` Borislav Petkov
2015-04-30 21:39 ` H. Peter Anvin
2015-04-30 23:23 ` H. Peter Anvin
2015-05-01 9:03 ` Borislav Petkov
2015-05-03 11:51 ` Borislav Petkov
2015-04-27 19:11 ` Borislav Petkov
2015-04-27 19:21 ` Denys Vlasenko
2015-04-27 19:45 ` Borislav Petkov
2015-04-28 13:40 ` Borislav Petkov
2015-04-27 16:12 ` Denys Vlasenko
2015-04-27 18:12 ` Linus Torvalds
2015-04-27 18:47 ` Borislav Petkov [this message]
2015-04-27 14:39 ` Borislav Petkov
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