From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754129AbdKJWDF (ORCPT ); Fri, 10 Nov 2017 17:03:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:51008 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750932AbdKJWDD (ORCPT ); Fri, 10 Nov 2017 17:03:03 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 23FB321996 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org X-Google-Smtp-Source: AGs4zMZBrvhDh0wUy5xkYWcRzOurghebJrCMOKbGN+bnxIVv1rSzBwvd13j1FCS6Bwsssu6narmPgSj2enmq1270E5Y= MIME-Version: 1.0 In-Reply-To: <20171110213717.12457-6-mathieu.desnoyers@efficios.com> References: <20171110213717.12457-1-mathieu.desnoyers@efficios.com> <20171110213717.12457-6-mathieu.desnoyers@efficios.com> From: Andy Lutomirski Date: Fri, 10 Nov 2017 14:02:41 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode To: Mathieu Desnoyers Cc: Boqun Feng , Peter Zijlstra , "Paul E . McKenney" , "linux-kernel@vger.kernel.org" , Linux API , Andy Lutomirski , Andrew Hunter , Maged Michael , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andrea Parri , Russell King , Greg Hackmann , Will Deacon , David Sehr , Linus Torvalds , X86 ML , linux-arch Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 10, 2017 at 1:37 PM, Mathieu Desnoyers wrote: > Introduce an architecture function that ensures the current CPU > issues a core serializing instruction before returning to usermode. > > This is needed to fix an existing core serialization bug on > thread migration, and also needed by the membarrier "sync_core" command. > > Architectures defining the sync_core_before_usermode() static inline > need to define ARCH_HAS_SYNC_CORE_BEFORE_USERMODE. > > Signed-off-by: Mathieu Desnoyers > CC: Peter Zijlstra > CC: Andy Lutomirski > CC: Paul E. McKenney > CC: Boqun Feng > CC: Andrew Hunter > CC: Maged Michael > CC: Avi Kivity > CC: Benjamin Herrenschmidt > CC: Paul Mackerras > CC: Michael Ellerman > CC: Dave Watson > CC: Thomas Gleixner > CC: Ingo Molnar > CC: "H. Peter Anvin" > CC: Andrea Parri > CC: Russell King > CC: Greg Hackmann > CC: Will Deacon > CC: David Sehr > CC: Linus Torvalds > CC: x86@kernel.org > CC: linux-arch@vger.kernel.org > --- > arch/x86/Kconfig | 1 + > arch/x86/include/asm/processor.h | 10 ++++++++++ > include/linux/processor.h | 6 ++++++ > 3 files changed, 17 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 01f78c1d40b5..54fbb8960d94 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -62,6 +62,7 @@ config X86 > select ARCH_HAS_SG_CHAIN > select ARCH_HAS_STRICT_KERNEL_RWX > select ARCH_HAS_STRICT_MODULE_RWX > + select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE > select ARCH_HAS_UBSAN_SANITIZE_ALL > select ARCH_HAS_ZONE_DEVICE if X86_64 > select ARCH_HAVE_NMI_SAFE_CMPXCHG > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > index bdac19ab2488..6ce996a7c730 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -706,6 +706,16 @@ static inline void sync_core(void) > #endif > } > > +/* > + * Ensure that a core serializing instruction is issued before returning > + * to user-mode. x86 implements return to user-space through sysexit and > + * sysretq, which are not core serializing. > + */ > +static inline void sync_core_before_usermode(void) > +{ > + sync_core(); > +} Make this if (!in_interrupt()) sync_core(); please. We can optimize it better later on. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode Date: Fri, 10 Nov 2017 14:02:41 -0800 Message-ID: References: <20171110213717.12457-1-mathieu.desnoyers@efficios.com> <20171110213717.12457-6-mathieu.desnoyers@efficios.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20171110213717.12457-6-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org To: Mathieu Desnoyers Cc: Boqun Feng , Peter Zijlstra , "Paul E . McKenney" , "linux-kernel@vger.kernel.org" , Linux API , Andy Lutomirski , Andrew Hunter , Maged Michael , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andrea Parri , Russell King , Greg Hackmann List-Id: linux-api@vger.kernel.org On Fri, Nov 10, 2017 at 1:37 PM, Mathieu Desnoyers wrote: > Introduce an architecture function that ensures the current CPU > issues a core serializing instruction before returning to usermode. > > This is needed to fix an existing core serialization bug on > thread migration, and also needed by the membarrier "sync_core" command. > > Architectures defining the sync_core_before_usermode() static inline > need to define ARCH_HAS_SYNC_CORE_BEFORE_USERMODE. > > Signed-off-by: Mathieu Desnoyers > CC: Peter Zijlstra > CC: Andy Lutomirski > CC: Paul E. McKenney > CC: Boqun Feng > CC: Andrew Hunter > CC: Maged Michael > CC: Avi Kivity > CC: Benjamin Herrenschmidt > CC: Paul Mackerras > CC: Michael Ellerman > CC: Dave Watson > CC: Thomas Gleixner > CC: Ingo Molnar > CC: "H. Peter Anvin" > CC: Andrea Parri > CC: Russell King > CC: Greg Hackmann > CC: Will Deacon > CC: David Sehr > CC: Linus Torvalds > CC: x86@kernel.org > CC: linux-arch@vger.kernel.org > --- > arch/x86/Kconfig | 1 + > arch/x86/include/asm/processor.h | 10 ++++++++++ > include/linux/processor.h | 6 ++++++ > 3 files changed, 17 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 01f78c1d40b5..54fbb8960d94 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -62,6 +62,7 @@ config X86 > select ARCH_HAS_SG_CHAIN > select ARCH_HAS_STRICT_KERNEL_RWX > select ARCH_HAS_STRICT_MODULE_RWX > + select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE > select ARCH_HAS_UBSAN_SANITIZE_ALL > select ARCH_HAS_ZONE_DEVICE if X86_64 > select ARCH_HAVE_NMI_SAFE_CMPXCHG > diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h > index bdac19ab2488..6ce996a7c730 100644 > --- a/arch/x86/include/asm/processor.h > +++ b/arch/x86/include/asm/processor.h > @@ -706,6 +706,16 @@ static inline void sync_core(void) > #endif > } > > +/* > + * Ensure that a core serializing instruction is issued before returning > + * to user-mode. x86 implements return to user-space through sysexit and > + * sysretq, which are not core serializing. > + */ > +static inline void sync_core_before_usermode(void) > +{ > + sync_core(); > +} Make this if (!in_interrupt()) sync_core(); please. We can optimize it better later on.