From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [PATCH for 4.16 07/11] x86: Implement sync_core_before_usermode (v3) Date: Wed, 17 Jan 2018 23:25:32 +0000 (UTC) Message-ID: <80094124.4887.1516231532603.JavaMail.zimbra@efficios.com> References: <20180117165458.13330-1-mathieu.desnoyers@efficios.com> <20180117165458.13330-8-mathieu.desnoyers@efficios.com> <712464074.4666.1516212636860.JavaMail.zimbra@efficios.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski Cc: Ingo Molnar , Peter Zijlstra , Thomas Gleixner , linux-kernel , linux-api , "Paul E. McKenney" , Boqun Feng , Andrew Hunter , maged michael , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , "H. Peter Anvin" , Andrea Parri , "Russell King, ARM Linux" , Greg Hackmann , Will Deacon , David List-Id: linux-arch.vger.kernel.org ----- On Jan 17, 2018, at 1:13 PM, Andy Lutomirski luto@kernel.org wrote: > On Wed, Jan 17, 2018 at 10:10 AM, Mathieu Desnoyers > wrote: >> ----- On Jan 17, 2018, at 12:53 PM, Andy Lutomirski luto@kernel.org wrote: >> >>> On Wed, Jan 17, 2018 at 8:54 AM, Mathieu Desnoyers >>> wrote: >>>> Ensure that a core serializing instruction is issued before returning to >>>> user-mode. x86 implements return to user-space through sysexit, sysrel, >>>> and sysretq, which are not core serializing. >>>> >>>> Signed-off-by: Mathieu Desnoyers >>>> Reviewed-by: Thomas Gleixner >>>> 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: 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 >>>> --- >>>> Changes since v1: >>>> - Fix prototype of sync_core_before_usermode in generic code (missing >>>> return type). >>>> - Add linux/processor.h include to sched/core.c. >>>> - Add ARCH_HAS_SYNC_CORE_BEFORE_USERMODE to init/Kconfig. >>>> - Fix linux/processor.h ifdef to target >>>> CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE rather than >>>> ARCH_HAS_SYNC_CORE_BEFORE_USERMODE. >>>> - Move empty static inline in processor.h to generic patch. >>>> --- >>>> arch/x86/Kconfig | 1 + >>>> arch/x86/include/asm/processor.h | 10 ++++++++++ >>>> 2 files changed, 11 insertions(+) >>>> >>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>>> index 20da391b5f32..0b44c8dd0e95 100644 >>>> --- a/arch/x86/Kconfig >>>> +++ b/arch/x86/Kconfig >>>> @@ -61,6 +61,7 @@ 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 d3a67fba200a..3257d34dbb40 100644 >>>> --- a/arch/x86/include/asm/processor.h >>>> +++ b/arch/x86/include/asm/processor.h >>>> @@ -722,6 +722,16 @@ 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, >>>> + * sysrel, and sysretq, which are not core serializing. >>>> + */ >>>> +static inline void sync_core_before_usermode(void) >>>> +{ >>> >>> /* With PTI, we unconditionally serialize before running user code. */ >>> if (static_cpu_has(X86_FEATURE_PTI)) >>> return; >> >> One issue I'm facing with this change is header dependency: >> sync_core_before_usermode() is currently implemented in >> arch/x86/include/asm/processor.h, but arch/x86/include/asm/cpufeature.h >> is needed for static_cpu_has, and it happens to include >> asm/processor.h. >> >> I'm facing a similar issue for adding a (in_irq() || in_nmi()) check. >> >> Should we move sync_core_before_usermode() to a different header, and if >> so, any suggestion ? > > tlbflush.h, maybe? Core serialization seems to be unrelated to TLB flushing though. I'm considering to create those new header files: include/asm-generic/sync_core.h (empty function) arch/x86/include/asm/sync_core.h for the sync_core_before_usermode() static inlines. Any better idea ? Thanks, Mathieu > >> >> Thanks, >> >> Mathieu >> >> >> >>> >>>> + sync_core(); >>>> +} >>> >>> --Andy >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. > > http://www.efficios.com -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.efficios.com ([167.114.142.141]:51966 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753031AbeAQXZg (ORCPT ); Wed, 17 Jan 2018 18:25:36 -0500 Date: Wed, 17 Jan 2018 23:25:32 +0000 (UTC) From: Mathieu Desnoyers Message-ID: <80094124.4887.1516231532603.JavaMail.zimbra@efficios.com> In-Reply-To: References: <20180117165458.13330-1-mathieu.desnoyers@efficios.com> <20180117165458.13330-8-mathieu.desnoyers@efficios.com> <712464074.4666.1516212636860.JavaMail.zimbra@efficios.com> Subject: Re: [PATCH for 4.16 07/11] x86: Implement sync_core_before_usermode (v3) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Andy Lutomirski Cc: Ingo Molnar , Peter Zijlstra , Thomas Gleixner , linux-kernel , linux-api , "Paul E. McKenney" , Boqun Feng , Andrew Hunter , maged michael , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , "H. Peter Anvin" , Andrea Parri , "Russell King, ARM Linux" , Greg Hackmann , Will Deacon , David Sehr , Linus Torvalds , x86 , linux-arch Message-ID: <20180117232532.1PAWszJYGBG1sEw1aBVBkHWmcIiqrpig_J5Ydalqrig@z> ----- On Jan 17, 2018, at 1:13 PM, Andy Lutomirski luto@kernel.org wrote: > On Wed, Jan 17, 2018 at 10:10 AM, Mathieu Desnoyers > wrote: >> ----- On Jan 17, 2018, at 12:53 PM, Andy Lutomirski luto@kernel.org wrote: >> >>> On Wed, Jan 17, 2018 at 8:54 AM, Mathieu Desnoyers >>> wrote: >>>> Ensure that a core serializing instruction is issued before returning to >>>> user-mode. x86 implements return to user-space through sysexit, sysrel, >>>> and sysretq, which are not core serializing. >>>> >>>> Signed-off-by: Mathieu Desnoyers >>>> Reviewed-by: Thomas Gleixner >>>> 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: 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 >>>> --- >>>> Changes since v1: >>>> - Fix prototype of sync_core_before_usermode in generic code (missing >>>> return type). >>>> - Add linux/processor.h include to sched/core.c. >>>> - Add ARCH_HAS_SYNC_CORE_BEFORE_USERMODE to init/Kconfig. >>>> - Fix linux/processor.h ifdef to target >>>> CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE rather than >>>> ARCH_HAS_SYNC_CORE_BEFORE_USERMODE. >>>> - Move empty static inline in processor.h to generic patch. >>>> --- >>>> arch/x86/Kconfig | 1 + >>>> arch/x86/include/asm/processor.h | 10 ++++++++++ >>>> 2 files changed, 11 insertions(+) >>>> >>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >>>> index 20da391b5f32..0b44c8dd0e95 100644 >>>> --- a/arch/x86/Kconfig >>>> +++ b/arch/x86/Kconfig >>>> @@ -61,6 +61,7 @@ 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 d3a67fba200a..3257d34dbb40 100644 >>>> --- a/arch/x86/include/asm/processor.h >>>> +++ b/arch/x86/include/asm/processor.h >>>> @@ -722,6 +722,16 @@ 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, >>>> + * sysrel, and sysretq, which are not core serializing. >>>> + */ >>>> +static inline void sync_core_before_usermode(void) >>>> +{ >>> >>> /* With PTI, we unconditionally serialize before running user code. */ >>> if (static_cpu_has(X86_FEATURE_PTI)) >>> return; >> >> One issue I'm facing with this change is header dependency: >> sync_core_before_usermode() is currently implemented in >> arch/x86/include/asm/processor.h, but arch/x86/include/asm/cpufeature.h >> is needed for static_cpu_has, and it happens to include >> asm/processor.h. >> >> I'm facing a similar issue for adding a (in_irq() || in_nmi()) check. >> >> Should we move sync_core_before_usermode() to a different header, and if >> so, any suggestion ? > > tlbflush.h, maybe? Core serialization seems to be unrelated to TLB flushing though. I'm considering to create those new header files: include/asm-generic/sync_core.h (empty function) arch/x86/include/asm/sync_core.h for the sync_core_before_usermode() static inlines. Any better idea ? Thanks, Mathieu > >> >> Thanks, >> >> Mathieu >> >> >> >>> >>>> + sync_core(); >>>> +} >>> >>> --Andy >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. > > http://www.efficios.com -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com