Messages in this thread Patch in this message | | | Date | Fri, 10 Nov 2017 22:20:30 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode |
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----- On Nov 10, 2017, at 5:02 PM, Andy Lutomirski luto@kernel.org wrote:
> On Fri, Nov 10, 2017 at 1:37 PM, Mathieu Desnoyers > <mathieu.desnoyers@efficios.com> 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 <mathieu.desnoyers@efficios.com> >> 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: Thomas Gleixner <tglx@linutronix.de> >> 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 >> --- >> 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.
Sure, done. It will be part of the next version of that patch.
Thanks!
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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