----- On Jan 17, 2018, at 1:13 PM, Andy Lutomirski [email protected] wrote: > On Wed, Jan 17, 2018 at 10:10 AM, Mathieu Desnoyers > <[email protected]> wrote: >> ----- On Jan 17, 2018, at 12:53 PM, Andy Lutomirski [email protected] wrote: >> >>> On Wed, Jan 17, 2018 at 8:54 AM, Mathieu Desnoyers >>> <[email protected]> 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 <[email protected]> >>>> Reviewed-by: Thomas Gleixner <[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: 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] >>>> --- >>>> 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
