From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: "thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
"luto@amacapital.net" <luto@amacapital.net>,
"Raslan, KarimAllah" <karahmed@amazon.de>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"ashok.raj@intel.com" <ashok.raj@intel.com>,
"arjan@linux.intel.com" <arjan@linux.intel.com>,
"arjan.van.de.ven@intel.com" <arjan.van.de.ven@intel.com>,
"bp@suse.de" <bp@suse.de>,
"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"Janakarajan.Natarajan@amd.com" <Janakarajan.Natarajan@amd.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"aarcange@redhat.com" <aarcange@redhat.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"luto@kernel.org" <luto@kernel.org>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"dave.hansen@intel.com" <dave.hansen@intel.com>,
"mhiramat@kernel.org" <mhiramat@kernel.org>,
"asit.k.mallick@intel.com" <asit.k.mallick@intel.com>,
"jun.nakajima@intel.com" <jun.nakajima@intel.com>,
"labbott@redhat.com" <labbott@redhat.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation
Date: Tue, 23 Jan 2018 16:20:58 +0000 [thread overview]
Message-ID: <1516724457.9521.156.camel@amazon.co.uk> (raw)
In-Reply-To: <4e01a7a9-29e4-adcc-3f53-550fb7f3d370@amd.com>
[-- Attachment #1.1: Type: text/plain, Size: 1585 bytes --]
On Tue, 2018-01-23 at 10:12 -0600, Tom Lendacky wrote:
>
> >> +.macro UNRESTRICT_IB_SPEC
> >> + ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> >> + PUSH_MSR_REGS
> >> + WRMSR_ASM $MSR_IA32_SPEC_CTRL, $0, $0
> >
> I think you should be writing 2, not 0, since I'm reasonably
> confident that we want STIBP on. Can you explain why you're writing
> 0?
>
> Do we want to talk about STIBP in general? Should it be (yet another)
> boot option to enable or disable? If there is STIBP support without
> IBRS support, it could be a set and forget at boot time.
We haven't got patches which enable STIBP in general. The kernel itself
is safe either way with retpoline, or because IBRS implies STIBP too
(that is, there's no difference between writing 1 and 3).
So STIBP is purely about protecting userspace processes from one
another, and VM guests from one another, when they run on HT siblings.
There's an argument that there are so many other information leaks
between HT siblings that we might not care. Especially as it's hard to
*tell* when you're scheduling, whether you trust all the processes (or
guests) on your HT siblings right now... let alone later when
scheduling another process if you need to *now* set STIBP on a sibling
which is no longer save from this process now running.
I'm not sure we want to set STIBP *unconditionally* either because of
the performance implications.
For IBRS we had an answer and it was just ugly. For STIBP we don't
actually have an answer for "how do we use this?". Do we?
[-- Attachment #1.2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5210 bytes --]
[-- Attachment #2.1: Type: text/plain, Size: 197 bytes --]
Amazon Web Services UK Limited. Registered in England and Wales with registration number 08650665 and which has its registered office at 60 Holborn Viaduct, London EC1A 2FD, United Kingdom.
[-- Attachment #2.2: Type: text/html, Size: 197 bytes --]
next prev parent reply other threads:[~2018-01-23 16:20 UTC|newest]
Thread overview: 161+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-20 19:22 [RFC 00/10] Speculation Control feature support KarimAllah Ahmed
2018-01-20 19:22 ` [RFC 01/10] x86/speculation: Add basic support for IBPB KarimAllah Ahmed
2018-01-20 19:22 ` [RFC 02/10] x86/kvm: Add IBPB support KarimAllah Ahmed
2018-01-20 20:18 ` Woodhouse, David
2018-01-22 18:56 ` Jim Mattson
2018-01-22 19:31 ` Jim Mattson
2018-01-20 19:22 ` [RFC 03/10] x86/speculation: Use Indirect Branch Prediction Barrier in context switch KarimAllah Ahmed
2018-01-20 19:22 ` [RFC 04/10] x86/mm: Only flush indirect branches when switching into non dumpable process KarimAllah Ahmed
2018-01-20 21:06 ` Woodhouse, David
2018-01-22 18:29 ` Tim Chen
2018-01-21 11:22 ` Peter Zijlstra
2018-01-21 12:04 ` David Woodhouse
2018-01-21 14:07 ` H.J. Lu
2018-01-22 10:19 ` Peter Zijlstra
2018-01-22 10:23 ` David Woodhouse
2018-01-21 16:21 ` Ingo Molnar
2018-01-21 16:25 ` Arjan van de Ven
2018-01-21 22:20 ` Woodhouse, David
2018-01-29 6:35 ` Jon Masters
2018-01-29 14:07 ` Peter Zijlstra
2018-01-20 19:22 ` [RFC 05/10] x86/speculation: Add basic IBRS support infrastructure KarimAllah Ahmed
2018-01-21 14:31 ` Thomas Gleixner
2018-01-21 14:56 ` Borislav Petkov
2018-01-22 9:51 ` Peter Zijlstra
2018-01-22 12:06 ` Borislav Petkov
2018-01-22 13:30 ` Greg Kroah-Hartman
2018-01-22 13:37 ` Woodhouse, David
2018-01-21 15:25 ` David Woodhouse
2018-01-23 20:58 ` David Woodhouse
2018-01-23 22:43 ` Johannes Erdfelt
2018-01-24 8:47 ` Peter Zijlstra
2018-01-24 9:02 ` David Woodhouse
2018-01-24 9:10 ` Greg Kroah-Hartman
2018-01-24 15:09 ` Arjan van de Ven
2018-01-24 15:18 ` David Woodhouse
2018-01-24 9:34 ` Peter Zijlstra
2018-01-24 10:49 ` Henrique de Moraes Holschuh
2018-01-24 12:30 ` David Woodhouse
2018-01-24 12:14 ` David Woodhouse
2018-01-24 12:29 ` Peter Zijlstra
2018-01-24 12:58 ` David Woodhouse
2018-01-29 20:14 ` [RFC,05/10] " Eduardo Habkost
2018-01-29 20:17 ` David Woodhouse
2018-01-29 20:42 ` Eduardo Habkost
2018-01-29 20:44 ` Arjan van de Ven
2018-01-29 21:02 ` David Woodhouse
2018-01-29 21:37 ` Jim Mattson
2018-01-29 21:50 ` Eduardo Habkost
2018-01-29 22:12 ` Jim Mattson
2018-01-30 1:22 ` Eduardo Habkost
2018-01-29 22:25 ` Andi Kleen
2018-01-30 1:37 ` Eduardo Habkost
2018-01-29 21:37 ` Andi Kleen
2018-01-29 21:44 ` Eduardo Habkost
2018-01-29 22:10 ` Konrad Rzeszutek Wilk
2018-01-30 1:12 ` Eduardo Habkost
2018-01-30 0:23 ` Linus Torvalds
2018-01-30 1:03 ` Jim Mattson
2018-01-30 3:13 ` Andi Kleen
2018-01-31 15:03 ` Paolo Bonzini
2018-01-31 15:07 ` Dr. David Alan Gilbert
2018-01-30 1:32 ` Arjan van de Ven
2018-01-30 3:32 ` Linus Torvalds
2018-01-30 12:04 ` Eduardo Habkost
2018-01-30 13:54 ` Arjan van de Ven
2018-01-30 8:22 ` David Woodhouse
2018-01-30 11:35 ` David Woodhouse
2018-01-30 11:56 ` Dr. David Alan Gilbert
2018-01-30 12:11 ` Christian Borntraeger
2018-01-30 14:46 ` Christophe de Dinechin
2018-01-30 14:52 ` Christian Borntraeger
2018-01-30 14:56 ` Christophe de Dinechin
2018-01-30 15:33 ` Christian Borntraeger
2018-01-30 20:46 ` Alan Cox
2018-01-31 10:05 ` Christophe de Dinechin
2018-01-31 10:15 ` Thomas Gleixner
2018-01-31 11:04 ` Dr. David Alan Gilbert
2018-01-31 11:52 ` Borislav Petkov
2018-01-31 12:30 ` Dr. David Alan Gilbert
2018-01-31 13:18 ` Borislav Petkov
2018-01-31 14:04 ` Dr. David Alan Gilbert
2018-01-31 14:44 ` Eduardo Habkost
2018-01-31 16:28 ` Borislav Petkov
2018-01-31 11:07 ` Christophe de Dinechin
2018-01-31 15:00 ` Eduardo Habkost
2018-01-31 15:11 ` Arjan van de Ven
2018-01-31 10:03 ` [RFC 05/10] " Christophe de Dinechin
2018-01-20 19:22 ` [RFC 06/10] x86/speculation: Add inlines to control Indirect Branch Speculation KarimAllah Ahmed
2018-01-20 19:22 ` [RFC 07/10] x86: Simplify spectre_v2 command line parsing KarimAllah Ahmed
2018-01-20 19:22 ` [RFC 08/10] x86/idle: Control Indirect Branch Speculation in idle KarimAllah Ahmed
2018-01-20 19:23 ` [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation KarimAllah Ahmed
2018-01-21 19:14 ` Andy Lutomirski
2018-01-23 16:12 ` Tom Lendacky
2018-01-23 16:20 ` Woodhouse, David [this message]
2018-01-23 22:37 ` Tom Lendacky
2018-01-23 22:49 ` Andi Kleen
2018-01-23 23:14 ` Woodhouse, David
2018-01-23 23:22 ` Andi Kleen
2018-01-24 0:47 ` Tim Chen
2018-01-24 1:00 ` Andy Lutomirski
2018-01-24 1:22 ` David Woodhouse
2018-01-24 1:59 ` Van De Ven, Arjan
2018-01-24 3:25 ` Andy Lutomirski
2018-01-21 19:34 ` Linus Torvalds
2018-01-21 20:28 ` David Woodhouse
2018-01-21 21:35 ` Linus Torvalds
2018-01-21 22:00 ` David Woodhouse
2018-01-21 22:27 ` Linus Torvalds
2018-01-22 16:27 ` David Woodhouse
2018-01-23 7:29 ` Ingo Molnar
2018-01-23 7:53 ` Ingo Molnar
2018-01-23 9:27 ` Ingo Molnar
2018-01-23 9:37 ` David Woodhouse
2018-01-23 15:01 ` Dave Hansen
2018-01-23 9:30 ` David Woodhouse
2018-01-23 10:15 ` Ingo Molnar
2018-01-23 10:27 ` David Woodhouse
2018-01-23 10:44 ` Ingo Molnar
2018-01-23 10:57 ` David Woodhouse
2018-01-23 10:23 ` Ingo Molnar
2018-01-23 10:35 ` David Woodhouse
2018-02-04 18:43 ` Thomas Gleixner
2018-02-04 20:22 ` David Woodhouse
2018-02-06 9:14 ` David Woodhouse
2018-01-25 16:19 ` Mason
2018-01-25 17:16 ` Greg Kroah-Hartman
2018-01-29 11:59 ` Mason
2018-01-24 0:05 ` Andi Kleen
2018-01-23 20:16 ` Pavel Machek
2018-01-20 19:23 ` [RFC 10/10] x86/enter: Use IBRS on syscall and interrupts KarimAllah Ahmed
2018-01-21 13:50 ` Konrad Rzeszutek Wilk
2018-01-21 14:40 ` KarimAllah Ahmed
2018-01-21 17:22 ` Dave Hansen
2018-01-21 14:02 ` [RFC 00/10] Speculation Control feature support Konrad Rzeszutek Wilk
2018-01-22 21:27 ` David Woodhouse
2018-01-22 22:15 [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Luke Kenneth Casson Leighton
2018-01-23 11:13 Liran Alon
2018-01-25 22:20 ` Dave Hansen
2018-01-26 2:11 Liran Alon
2018-01-26 2:23 ` Dave Hansen
2018-01-26 9:11 ` David Woodhouse
2018-01-26 17:19 ` Linus Torvalds
2018-01-26 17:27 ` Borislav Petkov
2018-01-26 17:29 ` David Woodhouse
2018-01-26 17:31 ` David Woodhouse
2018-01-26 17:59 ` Andi Kleen
2018-01-26 18:11 ` David Woodhouse
2018-01-26 18:12 ` Arjan van de Ven
2018-01-26 18:26 ` David Woodhouse
2018-01-26 18:28 ` Van De Ven, Arjan
2018-01-26 18:43 ` David Woodhouse
2018-01-26 18:44 ` Van De Ven, Arjan
2018-01-26 18:53 ` David Woodhouse
2018-01-26 19:02 ` Konrad Rzeszutek Wilk
2018-01-26 19:11 ` Hansen, Dave
2018-01-27 13:42 ` Konrad Rzeszutek Wilk
2018-01-27 15:55 ` Dave Hansen
2018-01-26 19:11 ` David Woodhouse
2018-01-26 8:46 ` David Woodhouse
2018-01-26 2:50 Liran Alon
2018-01-26 2:55 ` Van De Ven, Arjan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1516724457.9521.156.camel@amazon.co.uk \
--to=dwmw@amazon.co.uk \
--cc=Janakarajan.Natarajan@amd.com \
--cc=aarcange@redhat.com \
--cc=ak@linux.intel.com \
--cc=arjan.van.de.ven@intel.com \
--cc=arjan@linux.intel.com \
--cc=ashok.raj@intel.com \
--cc=asit.k.mallick@intel.com \
--cc=bp@suse.de \
--cc=dan.j.williams@intel.com \
--cc=dave.hansen@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=joro@8bytes.org \
--cc=jun.nakajima@intel.com \
--cc=karahmed@amazon.de \
--cc=kvm@vger.kernel.org \
--cc=labbott@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=luto@kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=rkrcmar@redhat.com \
--cc=tglx@linutronix.de \
--cc=thomas.lendacky@amd.com \
--cc=tim.c.chen@linux.intel.com \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
Powered by JetHome