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(); +} + extern void select_idle_routine(const struct cpuinfo_x86 *c); extern void amd_e400_c1e_apic_setup(void); diff --git a/include/linux/processor.h b/include/linux/processor.h index dbc952eec869..7d12e6fa050e 100644 --- a/include/linux/processor.h +++ b/include/linux/processor.h @@ -68,4 +68,10 @@ do { \ #endif +#ifndef ARCH_HAS_SYNC_CORE_BEFORE_USERMODE +static inline sync_core_before_usermode(void) +{ +} +#endif + #endif /* _LINUX_PROCESSOR_H */ -- 2.11.0
