> On Nov 10, 2017, at 2:20 PM, Mathieu Desnoyers <[email protected]> wrote:
>
> ----- On Nov 10, 2017, at 5:02 PM, Andy Lutomirski [email protected] wrote:
>
>> On Fri, Nov 10, 2017 at 1:37 PM, Mathieu Desnoyers
>> <[email protected]> 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 <[email protected]>
>>> CC: Peter Zijlstra <[email protected]>
>>> CC: Andy Lutomirski <[email protected]>
>>> CC: Paul E. McKenney <[email protected]>
>>> CC: Boqun Feng <[email protected]>
>>> CC: Andrew Hunter <[email protected]>
>>> CC: Maged Michael <[email protected]>
>>> CC: Avi Kivity <[email protected]>
>>> CC: Benjamin Herrenschmidt <[email protected]>
>>> CC: Paul Mackerras <[email protected]>
>>> CC: Michael Ellerman <[email protected]>
>>> CC: Dave Watson <[email protected]>
>>> CC: Thomas Gleixner <[email protected]>
>>> CC: Ingo Molnar <[email protected]>
>>> CC: "H. Peter Anvin" <[email protected]>
>>> CC: Andrea Parri <[email protected]>
>>> CC: Russell King <[email protected]>
>>> CC: Greg Hackmann <[email protected]>
>>> CC: Will Deacon <[email protected]>
>>> CC: David Sehr <[email protected]>
>>> CC: Linus Torvalds <[email protected]>
>>> CC: [email protected]
>>> CC: [email protected]
>>> ---
>>> 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!
Hmm. Can you also cc stable and make sure it applies by itself?
>
> Mathieu
>
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> --
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