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@xxxxxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxx>
CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CC: Boqun Feng <boqun.feng@xxxxxxxxx>
CC: Andrew Hunter <ahh@xxxxxxxxxx>
CC: Maged Michael <maged.michael@xxxxxxxxx>
CC: Avi Kivity <avi@xxxxxxxxxxxx>
CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
CC: Paul Mackerras <paulus@xxxxxxxxx>
CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
CC: Dave Watson <davejwatson@xxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
CC: Andrea Parri <parri.andrea@xxxxxxxxx>
CC: Russell King <linux@xxxxxxxxxxxxxxx>
CC: Greg Hackmann <ghackmann@xxxxxxxxxx>
CC: Will Deacon <will.deacon@xxxxxxx>
CC: David Sehr <sehr@xxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: x86@xxxxxxxxxx
CC: linux-arch@xxxxxxxxxxxxxxx
---
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();
+}
+
extern void select_idle_routine(const struct cpuinfo_x86 *c);
extern void amd_e400_c1e_apic_setup(void);
diff --git a/include/linux/processor.h b/include/linux/processor.h
index dbc952eec869..7d12e6fa050e 100644
--- a/include/linux/processor.h
+++ b/include/linux/processor.h
@@ -68,4 +68,10 @@ do { \
#endif
+#ifndef ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
+static inline sync_core_before_usermode(void)
+{
+}
+#endif
+
#endif /* _LINUX_PROCESSOR_H */
--
2.11.0
