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From: Peter Zijlstra <peterz@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andi Kleen <ak@linux.intel.com>,
	Arjan Van De Ven <arjan.van.de.ven@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>,
	Jason Baron <jbaron@akamai.com>
Subject: Re: [PATCH 20/24] objtool: Another static block fail
Date: Wed, 31 Jan 2018 11:27:50 +0100	[thread overview]
Message-ID: <20180131102750.GN2269@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1517393226.18619.156.camel@infradead.org>

On Wed, Jan 31, 2018 at 10:07:06AM +0000, David Woodhouse wrote:
> On Wed, 2018-01-31 at 11:01 +0100, Peter Zijlstra wrote:
> > On Tue, Jan 30, 2018 at 09:12:21PM -0600, Josh Poimboeuf wrote:
> > > 
> > > Or, maybe we should just forget the whole thing and just stick with the
> > > dynamic IBRS checks with lfence.  Yes, it's less ideal for the kernel,
> > > but adding these acrobatics to objtool also has a cost.
> > 
> > For now, IBRS seems off the table entirely. But no, I really don't want
> > to have to unconditionally eat the LFENCE cost in all those sites.
> 
> There's also alternatives. And without the IBRS-on-kernel-entry bits
> there aren't that many call sites that really need this anyway and
> don't have *other* conditionals that really are runtime-only (like
> dumpable etc.).

There is that.. So I think people wanted to use jump_labels for IBRS so
that we could runtime enable it when people loaded dodgy modules or
something. But even that we could all write in inline asm if needed I
suppose, it'll be ugly, but it should work.

  reply	other threads:[~2018-01-31 10:27 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-23 15:25 [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 01/24] objtool: Use existing global variables for options Peter Zijlstra
2018-01-23 15:25 ` [PATCH 02/24] objtool: Add retpoline validation Peter Zijlstra
2018-01-23 18:21   ` Borislav Petkov
2018-01-26  9:54   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 03/24] x86/paravirt: Annotate indirect calls Peter Zijlstra
2018-01-25 10:02   ` David Woodhouse
2018-01-25 10:22     ` Peter Zijlstra
2018-01-25 10:26       ` Juergen Gross
2018-01-25 10:52         ` David Woodhouse
2018-01-25 11:35           ` Peter Zijlstra
2018-01-26  9:57             ` David Woodhouse
2018-01-29 17:58   ` Josh Poimboeuf
2018-01-29 18:09     ` David Woodhouse
2018-01-29 18:17     ` Peter Zijlstra
2018-01-29 18:38   ` Josh Poimboeuf
2018-01-29 19:21     ` Peter Zijlstra
2018-01-30 16:02       ` Josh Poimboeuf
2018-01-31  4:13         ` [PATCH] x86/paravirt: Remove 'noreplace-paravirt' cmdline option Josh Poimboeuf
2018-01-31  5:59           ` Juergen Gross
2018-01-31  9:42           ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-23 15:25 ` [PATCH 04/24] x86,nospec: Annotate indirect calls/jumps Peter Zijlstra
2018-01-26 10:19   ` David Woodhouse
2018-01-29 17:44     ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 05/24] x86: Annotate indirect jump in head_64.S Peter Zijlstra
2018-01-26 10:24   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 06/24] x86,kvm: Fix indirect calls in emulator Peter Zijlstra
2018-01-23 20:28   ` Borislav Petkov
2018-01-23 20:48     ` David Woodhouse
2018-01-24 10:35       ` Peter Zijlstra
2018-01-24 10:43         ` Paolo Bonzini
2018-01-25  9:34           ` Peter Zijlstra
2018-01-25  9:49             ` David Woodhouse
2018-01-26 10:57             ` Paolo Bonzini
2018-01-23 15:25 ` [PATCH 07/24] x86,vmx: Fix indirect call Peter Zijlstra
2018-01-25  9:36   ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 08/24] x86,sme: Annotate " Peter Zijlstra
2018-01-26 10:37   ` David Woodhouse
2018-01-29 17:49     ` Peter Zijlstra
2018-01-29 17:50       ` Peter Zijlstra
2018-01-31  9:29     ` Peter Zijlstra
2018-01-31 15:04       ` Josh Poimboeuf
2018-01-31 16:00         ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 09/24] jump_label: Add branch hints to static_branch_{un,}likely() Peter Zijlstra
2018-01-24 18:46   ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 10/24] sched: Optimize ttwu_stat() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 11/24] x86: Reindent _static_cpu_has Peter Zijlstra
2018-01-23 15:25 ` [PATCH 12/24] x86: Update _static_cpu_has to use all named variables Peter Zijlstra
2018-01-25 19:31   ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 13/24] objtool: Implement base jump_assert support Peter Zijlstra
2018-01-26 10:45   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 14/24] x86: Add a type field to alt_instr Peter Zijlstra
2018-01-23 15:25 ` [PATCH 15/24] x86: Annotate static_cpu_has alternative Peter Zijlstra
2018-01-23 15:25 ` [PATCH 16/24] objtool: Implement jump_assert for _static_cpu_has() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 17/24] objtool: Introduce special_type Peter Zijlstra
2018-01-23 15:25 ` [PATCH 18/24] objtool: More complex static jump implementation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 19/24] objtool: Even more complex static block checks Peter Zijlstra
2018-01-23 15:25 ` [PATCH 20/24] objtool: Another static block fail Peter Zijlstra
2018-01-29 22:52   ` Josh Poimboeuf
2018-01-30  9:56     ` Peter Zijlstra
2018-01-31  3:12       ` Josh Poimboeuf
2018-01-31 10:01         ` Peter Zijlstra
2018-01-31 10:07           ` David Woodhouse
2018-01-31 10:27             ` Peter Zijlstra [this message]
2018-01-23 15:26 ` [PATCH 21/24] objtool: Skip static assert when KCOV/KASAN Peter Zijlstra
2018-01-23 15:26 ` [PATCH 22/24] x86/jump_label: Implement arch_static_assert() Peter Zijlstra
2018-01-23 15:26 ` [PATCH 23/24] x86: Force asm-goto Peter Zijlstra
2018-01-23 15:26 ` [PATCH 24/24] x86: Remove FAST_FEATURE_TESTS Peter Zijlstra
2018-01-23 15:42 ` [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:57   ` David Woodhouse
2018-01-23 16:03     ` Peter Zijlstra

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