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From: Thomas Gleixner <tglx@linutronix.de>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Waiman Long <longman9394@gmail.com>,
Jiri Kosina <jikos@kernel.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Andrea Arcangeli <aarcange@redhat.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Andi Kleen <ak@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Casey Schaufler <casey.schaufler@intel.com>,
Asit Mallick <asit.k.mallick@intel.com>,
Arjan van de Ven <arjan@linux.intel.com>,
Jon Masters <jcm@redhat.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [Patch v3 03/13] x86/speculation: Add static key for Enhanced IBRS
Date: Sun, 28 Oct 2018 10:32:38 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.21.1810281031520.2471@nanos.tec.linutronix.de> (raw)
In-Reply-To: <90d6723f-9cb9-e299-3e99-fa01c2518c29@linux.intel.com>
On Fri, 26 Oct 2018, Tim Chen wrote:
> On 10/26/2018 09:58 AM, Waiman Long wrote:
> >> @@ -386,6 +389,7 @@ static void __init spectre_v2_select_mitigation(void)
> >> /* Force it so VMEXIT will restore correctly */
> >> x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
> >> wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
> >> + static_branch_enable(&spectre_v2_enhanced_ibrs);
> >> goto specv2_set_mode;
> >> }
> >> if (IS_ENABLED(CONFIG_RETPOLINE))
> >
> > Why you need a static key for enhanced IBRS? It is supposed to be set at
> > boot time and never get changed after that. It will be easier to use a
> > feature bit for that instead. We usually use static key when the value
> > can be changed at run time.
> >
>
> We're close to running out of the feature bits. So I'm trying not to
> use those.
Software feature bits can be extended when needed. That's really a non issue.
Thanks,
tglx
next prev parent reply other threads:[~2018-10-28 9:44 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-17 17:59 [Patch v3 00/13] Provide process property based options to enable Spectre v2 userspace-userspace protection Tim Chen
2018-10-17 17:59 ` [Patch v3 01/13] x86/speculation: Clean up spectre_v2_parse_cmdline Tim Chen
2018-10-18 12:43 ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 02/13] x86/speculation: Remove unnecessary ret variable in cpu_show_common Tim Chen
2018-10-18 12:46 ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 03/13] x86/speculation: Add static key for Enhanced IBRS Tim Chen
2018-10-18 12:50 ` Thomas Gleixner
2018-10-26 16:58 ` Waiman Long
2018-10-26 18:15 ` Tim Chen
2018-10-28 9:32 ` Thomas Gleixner [this message]
2018-10-17 17:59 ` [Patch v3 04/13] x86/speculation: Disable STIBP when enhanced IBRS is in use Tim Chen
2018-10-18 12:58 ` Thomas Gleixner
2018-10-26 17:00 ` Waiman Long
2018-10-26 18:18 ` Tim Chen
2018-10-26 18:29 ` Tim Chen
2018-10-17 17:59 ` [Patch v3 05/13] x86/smt: Create cpu_smt_enabled static key for SMT specific code Tim Chen
2018-10-18 13:03 ` Thomas Gleixner
2018-10-19 7:51 ` Peter Zijlstra
2018-10-17 17:59 ` [Patch v3 06/13] mm: Pass task instead of task->mm as argument to set_dumpable Tim Chen
2018-10-18 13:22 ` Thomas Gleixner
2018-10-19 20:02 ` Peter Zijlstra
2018-10-17 17:59 ` [Patch v3 07/13] x86/process Add arch_set_dumpable Tim Chen
2018-10-18 13:28 ` Thomas Gleixner
2018-10-18 18:46 ` Tim Chen
2018-10-19 19:12 ` Thomas Gleixner
2018-10-19 20:16 ` Thomas Gleixner
2018-10-22 23:55 ` Tim Chen
2018-10-17 17:59 ` [Patch v3 08/13] x86/speculation: Rename SSBD update functions Tim Chen
2018-10-18 13:37 ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 09/13] x86/speculation: Reorganize SPEC_CTRL MSR update Tim Chen
2018-10-18 13:47 ` Thomas Gleixner
2018-10-26 17:21 ` Waiman Long
2018-10-26 18:25 ` Tim Chen
2018-10-17 17:59 ` [Patch v3 10/13] x86/speculation: Add per thread STIBP flag Tim Chen
2018-10-18 13:53 ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 11/13] x86/speculation: Add Spectre v2 lite app to app protection mode Tim Chen
2018-10-18 15:12 ` Thomas Gleixner
2018-10-17 17:59 ` [Patch v3 12/13] x86/speculation: Protect non-dumpable processes against Spectre v2 attack Tim Chen
2018-10-18 15:17 ` Thomas Gleixner
2018-10-26 17:46 ` Waiman Long
2018-10-26 18:10 ` Tim Chen
2018-10-17 17:59 ` [Patch v3 13/13] x86/speculation: Create PRCTL interface to restrict indirect branch speculation Tim Chen
2018-10-17 19:12 ` Randy Dunlap
2018-10-18 15:31 ` Thomas Gleixner
2018-10-19 7:57 ` [Patch v3 00/13] Provide process property based options to enable Spectre v2 userspace-userspace protection Peter Zijlstra
2018-10-19 16:43 ` Tim Chen
2018-10-19 18:38 ` Peter Zijlstra
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