On Wed, Jan 17, 2018 at 3:25 PM, Mathieu Desnoyers <[email protected]> wrote: > ----- 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 ?
Seems reasonable to me. Or maybe switch_to.h.
