From: Borislav Petkov <bp@amd64.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@amd64.org>, Andrew Lutomirski <luto@mit.edu>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>, Ingo Molnar <mingo@kernel.org>,
"user-mode-linux-devel@lists.sourceforge.net"
<user-mode-linux-devel@lists.sourceforge.net>,
Richard Weinberger <richard@nod.at>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>
Subject: Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)
Date: Tue, 23 Aug 2011 22:56:16 +0200 [thread overview]
Message-ID: <20110823205616.GA15295@aftab> (raw)
In-Reply-To: <4E53FC6E.1030807@zytor.com>
On Tue, Aug 23, 2011 at 03:15:58PM -0400, H. Peter Anvin wrote:
> Right, but if you had said the difference had disappeared on current AMD
> silicon it would be much less of an issue. That's why I wanted to find
> that bit out from you.
Yeah, I dug this out in the APM, btw.
But no, I don't think the difference has disappeared - to the contrary,
AFAICT, the intention is for SYSCALL to be the fastest way to do
syscalls on x86 due to diminished number of segment checks etc. INT80
is legacy, slower, etc. I believe Andy measured a similar situation on
Sandy Bridge with SYSCALL having latencies in the tens of nsecs range
and INT80 being much slower. Ingo also measured a similar situation
where the latency gap between the two on Intel is even bigger.
So, the only problem left now is what we're going
to do with cases similar to what Al conjured up:
http://marc.info/?l=linux-kernel&m=131412271112461&w=2
I don't know, maybe the most cowardly approach is to issue a warning and
shrug with the shoulders, or do some asm magic... Also, do we care at
all, how relevant is a case like that?
Hmmm.
--
Regards/Gruss,
Boris.
Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551
next prev parent reply other threads:[~2011-08-23 20:56 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-18 18:58 Subject: [PATCH 00/91] pending uml patches Al Viro
2011-08-18 19:12 ` Richard Weinberger
2011-08-18 19:19 ` Al Viro
2011-08-19 4:31 ` Al Viro
2011-08-19 8:51 ` Richard Weinberger
2011-08-20 1:18 ` [RFC] weird crap with vdso on uml/i386 Al Viro
2011-08-20 15:22 ` Richard Weinberger
2011-08-20 20:14 ` Al Viro
2011-08-20 20:55 ` Richard Weinberger
2011-08-20 21:26 ` Andrew Lutomirski
2011-08-20 21:38 ` Richard Weinberger
2011-08-20 21:40 ` Andrew Lutomirski
2011-08-21 6:34 ` Al Viro
2011-08-21 8:42 ` SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Al Viro
2011-08-21 11:24 ` Andrew Lutomirski
2011-08-21 13:37 ` Andrew Lutomirski
2011-08-21 14:51 ` Al Viro
2011-08-21 14:43 ` Al Viro
2011-08-21 16:41 ` Al Viro
2011-08-22 0:44 ` Andrew Lutomirski
2011-08-22 1:09 ` Linus Torvalds
2011-08-22 1:19 ` Al Viro
2011-08-22 1:19 ` H. Peter Anvin
2011-08-22 21:25 ` [tip:x86/urgent] x86-32, vdso: On system call restart after SYSENTER, use int $0x80 tip-bot for H. Peter Anvin
2011-08-23 23:40 ` tip-bot for H. Peter Anvin
2011-08-22 1:16 ` SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Al Viro
2011-08-22 1:41 ` Linus Torvalds
2011-08-22 1:48 ` H. Peter Anvin
2011-08-22 2:01 ` Andrew Lutomirski
2011-08-22 2:07 ` Al Viro
2011-08-22 2:26 ` Andrew Lutomirski
2011-08-22 2:34 ` H. Peter Anvin
2011-08-22 4:05 ` H. Peter Anvin
2011-08-22 9:53 ` [uml-devel] " Ingo Molnar
2011-08-22 13:34 ` Andrew Lutomirski
2011-08-22 14:40 ` Borislav Petkov
2011-08-22 15:13 ` Al Viro
2011-08-22 20:05 ` Linus Torvalds
2011-08-22 20:11 ` H. Peter Anvin
2011-08-22 21:52 ` Andrew Lutomirski
2011-08-22 22:04 ` H. Peter Anvin
2011-08-22 23:27 ` Linus Torvalds
2011-08-22 23:46 ` H. Peter Anvin
2011-08-23 0:03 ` Al Viro
2011-08-23 0:07 ` Al Viro
2011-08-23 0:07 ` H. Peter Anvin
2011-08-23 0:22 ` Linus Torvalds
2011-08-23 1:01 ` Al Viro
2011-08-23 1:13 ` Al Viro
2011-08-23 1:59 ` Linus Torvalds
2011-08-23 2:59 ` Al Viro
2011-08-23 2:17 ` Al Viro
2011-08-23 6:15 ` Al Viro
2011-08-23 14:26 ` Borislav Petkov
2011-08-23 16:30 ` Al Viro
2011-08-23 16:03 ` Linus Torvalds
2011-08-23 16:11 ` Andrew Lutomirski
2011-08-23 16:20 ` Linus Torvalds
2011-08-23 17:33 ` Al Viro
2011-08-23 18:04 ` Al Viro
2011-08-24 12:44 ` [PATCH] x86, asm: Document some of the syscall asm glue Borislav Petkov
2011-08-23 16:22 ` [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386) Borislav Petkov
2011-08-23 16:29 ` Linus Torvalds
2011-08-23 16:53 ` Al Viro
2011-08-23 16:58 ` Richard Weinberger
2011-08-23 17:07 ` Al Viro
2011-08-23 17:29 ` Richard Weinberger
2011-08-25 0:05 ` Richard Weinberger
2011-08-23 19:15 ` H. Peter Anvin
2011-08-23 20:56 ` Borislav Petkov [this message]
2011-08-23 21:06 ` H. Peter Anvin
2011-08-23 21:10 ` Borislav Petkov
2011-08-23 23:04 ` H. Peter Anvin
2011-08-24 21:10 ` H. Peter Anvin
2011-08-23 16:48 ` Al Viro
2011-08-23 17:33 ` Linus Torvalds
2011-08-23 21:08 ` H. Peter Anvin
2011-08-23 21:20 ` Linus Torvalds
2011-08-23 23:04 ` H. Peter Anvin
2011-08-23 19:18 ` H. Peter Anvin
2011-08-23 19:24 ` Linus Torvalds
2011-08-23 19:26 ` H. Peter Anvin
2011-08-23 19:41 ` Al Viro
2011-08-23 19:43 ` Linus Torvalds
2011-08-23 21:17 ` Al Viro
[not found] ` <CAObL_7FG8eFTZ4djKH0T8tbRf2h6+iOm=OXr8194nvzc+w+a9A@mail.gmail.com>
2011-08-23 1:18 ` H. Peter Anvin
2011-08-22 4:07 ` Al Viro
2011-08-22 4:11 ` H. Peter Anvin
2011-08-22 4:26 ` Al Viro
2011-08-22 5:03 ` H. Peter Anvin
2011-08-23 5:10 ` Andrew Lutomirski
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