Messages in this thread Patch in this message | | | Date | Wed, 17 Jan 2018 23:25:32 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH for 4.16 07/11] x86: Implement sync_core_before_usermode (v3) |
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----- On Jan 17, 2018, at 1:13 PM, Andy Lutomirski luto@kernel.org wrote:
> On Wed, Jan 17, 2018 at 10:10 AM, Mathieu Desnoyers > <mathieu.desnoyers@efficios.com> wrote: >> ----- On Jan 17, 2018, at 12:53 PM, Andy Lutomirski luto@kernel.org wrote: >> >>> On Wed, Jan 17, 2018 at 8:54 AM, Mathieu Desnoyers >>> <mathieu.desnoyers@efficios.com> 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 <mathieu.desnoyers@efficios.com> >>>> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> >>>> CC: Peter Zijlstra <peterz@infradead.org> >>>> CC: Andy Lutomirski <luto@kernel.org> >>>> CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com> >>>> CC: Boqun Feng <boqun.feng@gmail.com> >>>> CC: Andrew Hunter <ahh@google.com> >>>> CC: Maged Michael <maged.michael@gmail.com> >>>> CC: Avi Kivity <avi@scylladb.com> >>>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org> >>>> CC: Paul Mackerras <paulus@samba.org> >>>> CC: Michael Ellerman <mpe@ellerman.id.au> >>>> CC: Dave Watson <davejwatson@fb.com> >>>> CC: Ingo Molnar <mingo@redhat.com> >>>> CC: "H. Peter Anvin" <hpa@zytor.com> >>>> CC: Andrea Parri <parri.andrea@gmail.com> >>>> CC: Russell King <linux@armlinux.org.uk> >>>> CC: Greg Hackmann <ghackmann@google.com> >>>> CC: Will Deacon <will.deacon@arm.com> >>>> CC: David Sehr <sehr@google.com> >>>> CC: Linus Torvalds <torvalds@linux-foundation.org> >>>> CC: x86@kernel.org >>>> CC: linux-arch@vger.kernel.org >>>> --- >>>> 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
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