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From: Linus Torvalds <torvalds@linux-foundation.org>
To: KarimAllah Ahmed <karahmed@amazon.de>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Andi Kleen" <ak@linux.intel.com>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Arjan van de Ven" <arjan@linux.intel.com>,
	"Ashok Raj" <ashok.raj@intel.com>,
	"Asit Mallick" <asit.k.mallick@intel.com>,
	"Borislav Petkov" <bp@suse.de>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"David Woodhouse" <dwmw@amazon.co.uk>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"H . Peter Anvin" <hpa@zytor.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Janakarajan Natarajan" <Janakarajan.Natarajan@amd.com>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	"Laura Abbott" <labbott@redhat.com>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Tim Chen" <tim.c.chen@linux.intel.com>,
	"Tom Lendacky" <thomas.lendacky@amd.com>,
	kvm@vger.kernel.org, x86@kernel.org,
	"Arjan Van De Ven" <arjan.van.de.ven@intel.com>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation
Date: Sun, 21 Jan 2018 11:34:20 -0800
Message-ID: <CA+55aFxUEPHc7JRQG3zmxEsfmfJOiJa1QqFBKCBNb5Tt5vfiSg@mail.gmail.com> (raw)
In-Reply-To: <1516476182-5153-10-git-send-email-karahmed@amazon.de>


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All of this is pure garbage.

Is Intel really planning on making this shit architectural? Has anybody
talked to them and told them they are f*cking insane?

Please, any Intel engineers here - talk to your managers.

        Linus

On Jan 20, 2018 11:23, "KarimAllah Ahmed" <karahmed@amazon.de> wrote:

> From: Tim Chen <tim.c.chen@linux.intel.com>
>
> Create macros to control Indirect Branch Speculation.
>
> Name them so they reflect what they are actually doing.
> The macros are used to restrict and unrestrict the indirect branch
> speculation.
> They do not *disable* (or *enable*) indirect branch speculation. A trip
> back to
> user-space after *restricting* speculation would still affect the BTB.
>
> Quoting from a commit by Tim Chen:
>
> """
>     If IBRS is set, near returns and near indirect jumps/calls will not
> allow
>     their predicted target address to be controlled by code that executed
> in a
>     less privileged prediction mode *BEFORE* the IBRS mode was last
> written with
>     a value of 1 or on another logical processor so long as all Return
> Stack
>     Buffer (RSB) entries from the previous less privileged prediction mode
> are
>     overwritten.
>
>     Thus a near indirect jump/call/return may be affected by code in a less
>     privileged prediction mode that executed *AFTER* IBRS mode was last
> written
>     with a value of 1.
> """
>
> [ tglx: Changed macro names and rewrote changelog ]
> [ karahmed: changed macro names *again* and rewrote changelog ]
>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Greg KH <gregkh@linuxfoundation.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: David Woodhouse <dwmw@amazon.co.uk>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Link: https://lkml.kernel.org/r/3aab341725ee6a9aafd3141387453b
> 45d788d61a.1515542293.git.tim.c.chen@linux.intel.com
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>  arch/x86/entry/calling.h | 73 ++++++++++++++++++++++++++++++
> ++++++++++++++++++
>  1 file changed, 73 insertions(+)
>
> diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
> index 3f48f69..5aafb51 100644
> --- a/arch/x86/entry/calling.h
> +++ b/arch/x86/entry/calling.h
> @@ -6,6 +6,8 @@
>  #include <asm/percpu.h>
>  #include <asm/asm-offsets.h>
>  #include <asm/processor-flags.h>
> +#include <asm/msr-index.h>
> +#include <asm/cpufeatures.h>
>
>  /*
>
> @@ -349,3 +351,74 @@ For 32-bit we have the following conventions - kernel
> is built with
>  .Lafter_call_\@:
>  #endif
>  .endm
> +
> +/*
> + * IBRS related macros
> + */
> +.macro PUSH_MSR_REGS
> +       pushq   %rax
> +       pushq   %rcx
> +       pushq   %rdx
> +.endm
> +
> +.macro POP_MSR_REGS
> +       popq    %rdx
> +       popq    %rcx
> +       popq    %rax
> +.endm
> +
> +.macro WRMSR_ASM msr_nr:req edx_val:req eax_val:req
> +       movl    \msr_nr, %ecx
> +       movl    \edx_val, %edx
> +       movl    \eax_val, %eax
> +       wrmsr
> +.endm
> +
> +.macro RESTRICT_IB_SPEC
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       PUSH_MSR_REGS
> +       WRMSR_ASM $MSR_IA32_SPEC_CTRL, $0, $SPEC_CTRL_IBRS
> +       POP_MSR_REGS
> +.Lskip_\@:
> +.endm
> +
> +.macro UNRESTRICT_IB_SPEC
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       PUSH_MSR_REGS
> +       WRMSR_ASM $MSR_IA32_SPEC_CTRL, $0, $0
> +       POP_MSR_REGS
> +.Lskip_\@:
> +.endm
> +
> +.macro RESTRICT_IB_SPEC_CLOBBER
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       WRMSR_ASM $MSR_IA32_SPEC_CTRL, $0, $SPEC_CTRL_IBRS
> +.Lskip_\@:
> +.endm
> +
> +.macro UNRESTRICT_IB_SPEC_CLOBBER
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       WRMSR_ASM $MSR_IA32_SPEC_CTRL, $0, $0
> +.Lskip_\@:
> +.endm
> +
> +.macro RESTRICT_IB_SPEC_SAVE_AND_CLOBBER save_reg:req
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       movl    $MSR_IA32_SPEC_CTRL, %ecx
> +       rdmsr
> +       movl    %eax, \save_reg
> +       movl    $0, %edx
> +       movl    $SPEC_CTRL_IBRS, %eax
> +       wrmsr
> +.Lskip_\@:
> +.endm
> +
> +.macro RESTORE_IB_SPEC_CLOBBER save_reg:req
> +       ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_IBRS
> +       /* Set IBRS to the value saved in the save_reg */
> +       movl    $MSR_IA32_SPEC_CTRL, %ecx
> +       movl    $0, %edx
> +       movl    \save_reg, %eax
> +       wrmsr
> +.Lskip_\@:
> +.endm
> --
> 2.7.4
>
>

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  parent reply index

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
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 [this message]
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

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