From: David Woodhouse <dwmw2@infradead.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
Paul Turner <pjt@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
"Hansen, Dave" <dave.hansen@intel.com>,
Andi Kleen <ak@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/7] IBRS patch series
Date: Fri, 05 Jan 2018 16:46:40 +0000 [thread overview]
Message-ID: <1515170800.29312.152.camel@infradead.org> (raw)
In-Reply-To: <20180105164245.GW26807@redhat.com>
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On Fri, 2018-01-05 at 17:42 +0100, Andrea Arcangeli wrote:
> On Fri, Jan 05, 2018 at 04:37:30PM +0000, David Woodhouse wrote:
> > You are completely ignoring pre-Skylake here.
> >
> > On pre-Skylake, retpoline is perfectly sufficient and it's a *lot*
> > faster than the IBRS option which is almost prohibitively slow.
> >
> > We didn't do it just for fun. And it's working fine; it isn't *that*
> > complex.
>
> How do you enable IBRS when the CPU switches to SMM?
SMM is fine, as Arjan said. It's only for stuff like EFI runtime calls,
and then only if you're really paranoid.
> Do you already have this 2-way code emission from gcc and patching
> with a 3-way alternatives at boot between ibrs and 2 reptoline version
> emitted by gcc and alternatives between ibrs and ibpb where SPEC_CTRL
> is missing on some CPU but IBPB_SUPPORT is available?
This was implemented in Intel's patch sets that they've been sending
out. I don't really know why we've suddenly gone back to the drawing
board and turned things around to put retpoline first in the series,
etc.
I'm also mildly concerned that all the variant 1 patches have just
disappeared.
> Or are you talking about having done this on a non upstream Xen build
> only without the 2-way code emission for gcc?
Xen has it too, but no. I was talking about Linux.
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next prev parent reply other threads:[~2018-01-05 16:46 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-04 17:56 Tim Chen
2018-01-04 17:56 ` [PATCH 1/7] x86/feature: Detect the x86 feature to control Speculation Tim Chen
2018-01-04 19:58 ` Greg KH
2018-01-04 20:47 ` Tim Chen
2018-01-05 11:14 ` David Woodhouse
2018-01-05 15:14 ` Tom Lendacky
2018-01-05 17:07 ` Tim Chen
2018-01-05 13:09 ` Thomas Gleixner
2018-01-05 13:44 ` Andrea Arcangeli
2018-01-05 13:51 ` Thomas Gleixner
2018-01-04 17:56 ` [PATCH 2/7] x86/enter: MACROS to set/clear IBRS Tim Chen
2018-01-04 22:16 ` Peter Zijlstra
2018-01-04 22:21 ` Tim Chen
2018-01-04 22:23 ` Dave Hansen
2018-01-05 4:54 ` Andy Lutomirski
2018-01-05 5:05 ` Dave Hansen
2018-01-05 13:19 ` Thomas Gleixner
2018-01-04 17:56 ` [PATCH 3/7] x86/enter: Use IBRS on syscall and interrupts Tim Chen
2018-01-04 20:00 ` Greg KH
2018-01-04 20:26 ` Tim Chen
2018-01-04 20:45 ` Dave Hansen
2018-01-04 22:33 ` Peter Zijlstra
2018-01-04 23:12 ` Andrea Arcangeli
2018-01-05 0:08 ` Dave Hansen
2018-01-05 4:51 ` Andy Lutomirski
2018-01-05 5:11 ` Dave Hansen
2018-01-05 12:01 ` Alan Cox
2018-01-05 13:35 ` Thomas Gleixner
2018-01-04 17:56 ` [PATCH 4/7] x86/idle: Disable IBRS entering idle and enable it on wakeup Tim Chen
2018-01-04 22:47 ` Peter Zijlstra
2018-01-04 23:00 ` Andrea Arcangeli
2018-01-04 23:22 ` Tim Chen
2018-01-04 23:42 ` Andrea Arcangeli
2018-01-04 23:45 ` Thomas Gleixner
2018-01-05 0:03 ` Andrea Arcangeli
2018-01-08 8:24 ` Peter Zijlstra
2018-01-04 17:56 ` [PATCH 5/7] x86: Use IBRS for firmware update path Tim Chen
2018-01-04 18:48 ` Alan Cox
2018-01-04 20:05 ` Greg KH
2018-01-04 20:08 ` Woodhouse, David
2018-01-05 16:08 ` gregkh
2018-01-05 16:37 ` Andrea Arcangeli
2018-01-04 20:21 ` Andrew Cooper
2018-01-04 20:48 ` Andrea Arcangeli
2018-01-04 20:51 ` Yves-Alexis Perez
2018-01-04 21:13 ` Tim Chen
2018-01-04 22:51 ` Peter Zijlstra
2018-01-05 13:40 ` Thomas Gleixner
2018-01-04 17:56 ` [PATCH 6/7] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature Tim Chen
2018-01-04 18:33 ` Borislav Petkov
2018-01-04 18:36 ` Dave Hansen
2018-01-04 18:52 ` Borislav Petkov
2018-01-04 18:57 ` Andrea Arcangeli
2018-01-04 18:59 ` Dave Hansen
2018-01-04 19:06 ` Borislav Petkov
2018-01-05 13:48 ` Thomas Gleixner
2018-01-04 18:38 ` Andrea Arcangeli
2018-01-04 18:54 ` Dave Hansen
2018-01-04 18:56 ` Borislav Petkov
2018-01-04 18:55 ` Borislav Petkov
2018-01-04 18:34 ` Andrea Arcangeli
2018-01-04 19:02 ` Tim Chen
2018-01-04 18:50 ` Alan Cox
2018-01-04 20:16 ` Greg KH
2018-01-04 20:58 ` Tim Chen
2018-01-04 22:54 ` Peter Zijlstra
2018-01-04 23:26 ` Tim Chen
2018-01-04 23:51 ` Andrea Arcangeli
2018-01-04 23:59 ` Borislav Petkov
2018-01-05 0:07 ` Thomas Gleixner
2018-01-05 11:16 ` David Woodhouse
2018-01-06 1:29 ` Tim Chen
2018-01-04 17:56 ` [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode reload Tim Chen
2018-01-04 18:28 ` Borislav Petkov
2018-01-04 18:34 ` Andrea Arcangeli
2018-01-04 18:50 ` Borislav Petkov
2018-01-04 19:10 ` Tim Chen
2018-01-05 13:32 ` Greg KH
2018-01-05 13:37 ` Borislav Petkov
2018-01-05 13:47 ` Greg KH
2018-01-05 15:28 ` Andrea Arcangeli
2018-01-04 19:00 ` [PATCH 0/7] IBRS patch series Linus Torvalds
2018-01-04 19:19 ` David Woodhouse
2018-01-04 19:33 ` Linus Torvalds
2018-01-04 19:39 ` David Woodhouse
2018-01-04 19:40 ` Andrew Cooper
2018-01-04 19:46 ` David Woodhouse
2018-01-04 21:22 ` Van De Ven, Arjan
2018-01-05 11:32 ` Paolo Bonzini
2018-01-05 12:09 ` Paul Turner
2018-01-05 14:45 ` Van De Ven, Arjan
2018-01-05 14:43 ` Andrea Arcangeli
2018-01-05 14:52 ` Van De Ven, Arjan
2018-01-05 15:03 ` Andrea Arcangeli
2018-01-05 14:54 ` Thomas Gleixner
2018-01-05 11:52 ` Paul Turner
2018-01-05 14:28 ` David Woodhouse
2018-01-05 14:42 ` Van De Ven, Arjan
2018-01-05 15:38 ` David Woodhouse
2018-01-05 16:05 ` Andrea Arcangeli
2018-01-05 16:37 ` David Woodhouse
2018-01-05 16:42 ` Andrea Arcangeli
2018-01-05 16:44 ` Van De Ven, Arjan
2018-01-05 16:46 ` David Woodhouse [this message]
2018-01-05 5:25 ` Florian Weimer
2018-01-05 11:05 ` David Woodhouse
2018-01-04 19:05 ` Justin Forbes
2018-01-04 19:10 ` Tim Chen
2018-01-04 21:01 ` Yves-Alexis Perez
2018-01-05 13:28 ` Greg KH
2018-01-05 13:47 ` Yves-Alexis Perez
2018-01-05 14:01 ` Greg KH
2018-01-05 14:26 ` Paolo Bonzini
2018-01-05 14:54 ` Yves-Alexis Perez
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