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.
