Messages in this thread | | | From | Andy Lutomirski <> | Date | Fri, 10 Nov 2017 14:02:41 -0800 | Subject | Re: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode |
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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.
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