From: Jon Masters <jcm@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Encrypted Message
Date: Mon, 4 Mar 2019 02:45:53 -0500 [thread overview]
Message-ID: <7c8680f2-efe4-a603-ab7e-6b88fb37d76f@redhat.com> (raw)
In-Reply-To: <20190304073049.GA23573@kroah.com>
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From: Jon Masters <jcm@redhat.com>
To: speck for Greg KH <speck@linutronix.de>
Subject: Re: [PATCH RFC 1/4] 1
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On 3/4/19 2:30 AM, speck for Greg KH wrote:
> On Sun, Mar 03, 2019 at 07:23:22PM -0600, speck for Josh Poimboeuf wrote:
>> From: Josh Poimboeuf <jpoimboe@redhat.com>
>> Subject: [PATCH RFC 1/4] x86/speculation/mds: Add mds=full,nosmt cmdline
>> option
>>
>> Add the mds=full,nosmt cmdline option. This is like mds=full, but with
>> SMT disabled if the CPU is vulnerable.
>>
>> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
>> ---
>> Documentation/admin-guide/hw-vuln/mds.rst | 3 +++
>> Documentation/admin-guide/kernel-parameters.txt | 6 ++++--
>> arch/x86/kernel/cpu/bugs.c | 10 ++++++++++
>> 3 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/hw-vuln/mds.rst b/Documentation/admin-guide/hw-vuln/mds.rst
>> index 1de29d28903d..244ab47d1fb3 100644
>> --- a/Documentation/admin-guide/hw-vuln/mds.rst
>> +++ b/Documentation/admin-guide/hw-vuln/mds.rst
>> @@ -260,6 +260,9 @@ time with the option "mds=". The valid arguments for this option are:
>>
>> It does not automatically disable SMT.
>>
>> + full,nosmt The same as mds=full, with SMT disabled on vulnerable
>> + CPUs. This is the complete mitigation.
>
> While I understand the intention, the number of different combinations
> we are "offering" to userspace here is huge, and everyone is going to be
> confused as to what to do. If we really think/say that SMT is a major
> issue for this, why don't we just have "full" disable SMT?
Frankly, it ought to for safety (can't be made safe). The reason cited
for not doing so (Thomas and Linus can speak up on this part) was
upgrades vs new installs. The concern was not to break existing folks by
losing half their logical CPU count when upgrading a kernel.
Jon.
--
Computer Architect | Sent with my Fedora powered laptop
next prev parent reply other threads:[~2019-03-04 7:46 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-04 1:21 [MODERATED] [PATCH RFC 0/4] Proposed cmdline improvements Josh Poimboeuf
2019-03-04 1:23 ` [MODERATED] [PATCH RFC 1/4] 1 Josh Poimboeuf
2019-03-04 3:55 ` [MODERATED] Encrypted Message Jon Masters
2019-03-04 17:06 ` [MODERATED] " Josh Poimboeuf
2019-03-04 7:30 ` [MODERATED] Re: [PATCH RFC 1/4] 1 Greg KH
2019-03-04 7:45 ` Jon Masters [this message]
2019-03-04 1:24 ` [MODERATED] [PATCH RFC 2/4] 2 Josh Poimboeuf
2019-03-04 7:31 ` [MODERATED] " Greg KH
2019-03-04 17:11 ` Josh Poimboeuf
2019-03-04 1:24 ` [MODERATED] [PATCH RFC 3/4] 3 Josh Poimboeuf
2019-03-04 3:58 ` [MODERATED] Encrypted Message Jon Masters
2019-03-04 17:17 ` [MODERATED] " Josh Poimboeuf
2019-03-06 16:22 ` [MODERATED] " Jon Masters
2019-03-04 7:33 ` [MODERATED] Re: [PATCH RFC 3/4] 3 Greg KH
2019-03-04 17:18 ` Josh Poimboeuf
2019-03-04 1:25 ` [MODERATED] [PATCH RFC 4/4] 4 Josh Poimboeuf
2019-03-04 4:07 ` [MODERATED] Encrypted Message Jon Masters
-- strict thread matches above, loose matches on Subject: below --
2019-03-05 16:43 [MODERATED] Starting to go public? Linus Torvalds
2019-03-05 17:02 ` [MODERATED] " Andrew Cooper
2019-03-05 20:36 ` Jiri Kosina
2019-03-05 22:31 ` Andrew Cooper
2019-03-06 16:18 ` [MODERATED] Encrypted Message Jon Masters
2019-03-05 17:10 ` Jon Masters
2019-03-01 21:47 [patch V6 00/14] MDS basics 0 Thomas Gleixner
2019-03-01 21:47 ` [patch V6 06/14] MDS basics 6 Thomas Gleixner
2019-03-04 6:28 ` [MODERATED] Encrypted Message Jon Masters
2019-03-01 21:47 ` [patch V6 08/14] MDS basics 8 Thomas Gleixner
2019-03-04 6:57 ` [MODERATED] Encrypted Message Jon Masters
2019-03-04 7:06 ` Jon Masters
2019-03-04 8:12 ` Jon Masters
2019-03-05 15:34 ` Thomas Gleixner
2019-03-06 16:21 ` [MODERATED] " Jon Masters
2019-03-01 21:47 ` [patch V6 10/14] MDS basics 10 Thomas Gleixner
2019-03-04 6:45 ` [MODERATED] Encrypted Message Jon Masters
2019-03-01 21:47 ` [patch V6 12/14] MDS basics 12 Thomas Gleixner
2019-03-04 5:47 ` [MODERATED] Encrypted Message Jon Masters
2019-03-04 5:30 ` Jon Masters
2019-02-24 15:07 [MODERATED] [PATCH v6 00/43] MDSv6 Andi Kleen
2019-02-24 15:07 ` [MODERATED] [PATCH v6 10/43] MDSv6 Andi Kleen
2019-02-25 16:30 ` [MODERATED] " Greg KH
2019-02-25 16:41 ` [MODERATED] Encrypted Message Jon Masters
2019-02-24 15:07 ` [MODERATED] [PATCH v6 31/43] MDSv6 Andi Kleen
2019-02-25 15:19 ` [MODERATED] " Greg KH
2019-02-25 15:34 ` Andi Kleen
2019-02-25 15:49 ` Greg KH
2019-02-25 15:52 ` [MODERATED] Encrypted Message Jon Masters
2019-02-25 16:00 ` [MODERATED] " Greg KH
2019-02-25 16:19 ` [MODERATED] " Jon Masters
2019-02-22 22:24 [patch V4 00/11] MDS basics Thomas Gleixner
2019-02-22 22:24 ` [patch V4 04/11] x86/speculation/mds: Add mds_clear_cpu_buffer() Thomas Gleixner
2019-02-26 14:19 ` [MODERATED] " Josh Poimboeuf
2019-03-01 20:58 ` [MODERATED] Encrypted Message Jon Masters
2019-03-01 22:14 ` Jon Masters
2019-02-21 23:44 [patch V3 0/9] MDS basics 0 Thomas Gleixner
2019-02-21 23:44 ` [patch V3 4/9] MDS basics 4 Thomas Gleixner
2019-02-22 7:45 ` [MODERATED] Encrypted Message Jon Masters
2019-02-20 15:07 [patch V2 00/10] MDS basics+ 0 Thomas Gleixner
2019-02-20 15:07 ` [patch V2 04/10] MDS basics+ 4 Thomas Gleixner
2019-02-20 17:10 ` [MODERATED] " mark gross
2019-02-21 19:26 ` [MODERATED] Encrypted Message Tim Chen
2019-02-19 12:44 [patch 0/8] MDS basics 0 Thomas Gleixner
2019-02-21 16:14 ` [MODERATED] Encrypted Message Jon Masters
2019-02-07 23:41 [MODERATED] [PATCH v3 0/6] PERFv3 Andi Kleen
2019-02-07 23:41 ` [MODERATED] [PATCH v3 2/6] PERFv3 Andi Kleen
2019-02-08 0:51 ` [MODERATED] Re: [SUSPECTED SPAM][PATCH " Andrew Cooper
2019-02-08 9:01 ` Peter Zijlstra
2019-02-08 9:39 ` Peter Zijlstra
2019-02-08 10:53 ` [MODERATED] [RFC][PATCH] performance walnuts Peter Zijlstra
2019-02-15 23:45 ` [MODERATED] Encrypted Message Jon Masters
2019-01-12 1:29 [MODERATED] [PATCH v4 00/28] MDSv4 2 Andi Kleen
2019-01-12 1:29 ` [MODERATED] [PATCH v4 05/28] MDSv4 10 Andi Kleen
2019-01-14 19:20 ` [MODERATED] " Dave Hansen
2019-01-18 7:33 ` [MODERATED] Encrypted Message Jon Masters
2019-01-14 23:39 ` Tim Chen
2019-01-12 1:29 ` [MODERATED] [PATCH v4 10/28] MDSv4 24 Andi Kleen
2019-01-15 1:05 ` [MODERATED] Encrypted Message Tim Chen
2018-06-12 17:29 [MODERATED] FYI - Reading uncached memory Jon Masters
2018-06-14 16:59 ` [MODERATED] Encrypted Message Tim Chen
2018-05-29 19:42 [MODERATED] [PATCH 0/2] L1TF KVM 0 Paolo Bonzini
[not found] ` <20180529194240.7F1336110A@crypto-ml.lab.linutronix.de>
2018-05-29 22:49 ` [PATCH 1/2] L1TF KVM 1 Thomas Gleixner
2018-05-29 23:54 ` [MODERATED] " Andrew Cooper
2018-05-30 9:01 ` Paolo Bonzini
2018-06-04 8:24 ` [MODERATED] " Martin Pohlack
2018-06-04 13:11 ` [MODERATED] Is: Tim, Q to you. Was:Re: " Konrad Rzeszutek Wilk
2018-06-04 17:59 ` [MODERATED] Encrypted Message Tim Chen
2018-06-05 23:34 ` Tim Chen
2018-06-05 23:37 ` Tim Chen
2018-06-07 19:11 ` Tim Chen
2018-05-17 20:53 SSB status - V18 pushed out Thomas Gleixner
2018-05-18 13:54 ` [MODERATED] Is: Sleep states ?Was:Re: " Konrad Rzeszutek Wilk
2018-05-18 14:29 ` Thomas Gleixner
2018-05-18 19:50 ` [MODERATED] Encrypted Message Tim Chen
2018-05-02 21:51 [patch V11 00/16] SSB 0 Thomas Gleixner
2018-05-03 4:27 ` [MODERATED] Encrypted Message Tim Chen
2018-04-24 9:06 [MODERATED] L1D-Fault KVM mitigation Joerg Roedel
2018-04-24 9:35 ` [MODERATED] " Peter Zijlstra
2018-04-24 9:48 ` David Woodhouse
2018-04-24 11:04 ` Peter Zijlstra
2018-05-23 9:45 ` David Woodhouse
2018-05-24 9:45 ` Peter Zijlstra
2018-05-24 15:04 ` Thomas Gleixner
2018-05-24 15:33 ` Thomas Gleixner
2018-05-24 23:18 ` [MODERATED] Encrypted Message Tim Chen
2018-05-25 18:22 ` Tim Chen
2018-05-26 19:14 ` L1D-Fault KVM mitigation Thomas Gleixner
2018-05-29 19:29 ` [MODERATED] Encrypted Message Tim Chen
2018-05-29 21:14 ` L1D-Fault KVM mitigation Thomas Gleixner
2018-05-30 16:38 ` [MODERATED] Encrypted Message Tim Chen
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