lkml.org 
[lkml]   [2017]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode
----- On Nov 10, 2017, at 5:02 PM, Andy Lutomirski luto@kernel.org wrote:

> On Fri, Nov 10, 2017 at 1:37 PM, Mathieu Desnoyers
> <mathieu.desnoyers@efficios.com> 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 <mathieu.desnoyers@efficios.com>
>> CC: Peter Zijlstra <peterz@infradead.org>
>> CC: Andy Lutomirski <luto@kernel.org>
>> CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>> CC: Boqun Feng <boqun.feng@gmail.com>
>> CC: Andrew Hunter <ahh@google.com>
>> CC: Maged Michael <maged.michael@gmail.com>
>> CC: Avi Kivity <avi@scylladb.com>
>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> CC: Paul Mackerras <paulus@samba.org>
>> CC: Michael Ellerman <mpe@ellerman.id.au>
>> CC: Dave Watson <davejwatson@fb.com>
>> CC: Thomas Gleixner <tglx@linutronix.de>
>> CC: Ingo Molnar <mingo@redhat.com>
>> CC: "H. Peter Anvin" <hpa@zytor.com>
>> CC: Andrea Parri <parri.andrea@gmail.com>
>> CC: Russell King <linux@armlinux.org.uk>
>> CC: Greg Hackmann <ghackmann@google.com>
>> CC: Will Deacon <will.deacon@arm.com>
>> CC: David Sehr <sehr@google.com>
>> CC: Linus Torvalds <torvalds@linux-foundation.org>
>> 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.

Sure, done. It will be part of the next version of that patch.

Thanks!

Mathieu


--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
\
 
 \ /
  Last update: 2017-11-10 23:20    [W:0.305 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site