[RFC PATCH v2 for 4.15 15/24] membarrier: selftest: Test private expedited cmd

[RFC PATCH v2 for 4.15 15/24] membarrier: selftest: Test private expedited cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED and
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED commands.

Add checks expecting specific error values on system calls expected to
fail.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
Changes since v1:
- return result of ksft_exit_pass from main(), silencing compiler
  warning about missing return value.
---
 .../testing/selftests/membarrier/membarrier_test.c | 111 ++++++++++++++++++---
 1 file changed, 95 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index 9e674d9514d1..e6ee73d01fa1 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -16,49 +16,119 @@ static int sys_membarrier(int cmd, int flags)
 static int test_membarrier_cmd_fail(void)
 {
 	int cmd = -1, flags = 0;
+	const char *test_name = "sys membarrier invalid command";
 
 	if (sys_membarrier(cmd, flags) != -1) {
 		ksft_exit_fail_msg(
-			"sys membarrier invalid command test: command = %d, flags = %d. Should fail, but passed\n",
-			cmd, flags);
+			"%s test: command = %d, flags = %d. Should fail, but passed\n",
+			test_name, cmd, flags);
+	}
+	if (errno != EINVAL) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EINVAL, strerror(EINVAL),
+			errno, strerror(errno));
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier invalid command test: command = %d, flags = %d. Failed as expected\n",
-		cmd, flags);
+		"%s test: command = %d, flags = %d, errno = %d. Failed as expected\n",
+		test_name, cmd, flags, errno);
 	return 0;
 }
 
 static int test_membarrier_flags_fail(void)
 {
 	int cmd = MEMBARRIER_CMD_QUERY, flags = 1;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_QUERY invalid flags";
 
 	if (sys_membarrier(cmd, flags) != -1) {
 		ksft_exit_fail_msg(
-			"sys membarrier MEMBARRIER_CMD_QUERY invalid flags test: flags = %d. Should fail, but passed\n",
-			flags);
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EINVAL) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EINVAL, strerror(EINVAL),
+			errno, strerror(errno));
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier MEMBARRIER_CMD_QUERY invalid flags test: flags = %d. Failed as expected\n",
-		flags);
+		"%s test: flags = %d, errno = %d. Failed as expected\n",
+		test_name, flags, errno);
 	return 0;
 }
 
-static int test_membarrier_success(void)
+static int test_membarrier_shared_success(void)
 {
 	int cmd = MEMBARRIER_CMD_SHARED, flags = 0;
-	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED\n";
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n", test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_fail(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED not registered failure";
+
+	if (sys_membarrier(cmd, flags) != -1) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EPERM) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EPERM, strerror(EPERM),
+			errno, strerror(errno));
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d, errno = %d\n",
+		test_name, flags, errno);
+	return 0;
+}
+
+static int test_membarrier_register_private_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED";
 
 	if (sys_membarrier(cmd, flags) != 0) {
 		ksft_exit_fail_msg(
-			"sys membarrier MEMBARRIER_CMD_SHARED test: flags = %d\n",
-			flags);
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier MEMBARRIER_CMD_SHARED test: flags = %d\n",
-		flags);
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
 	return 0;
 }
 
@@ -72,7 +142,16 @@ static int test_membarrier(void)
 	status = test_membarrier_flags_fail();
 	if (status)
 		return status;
-	status = test_membarrier_success();
+	status = test_membarrier_shared_success();
+	if (status)
+		return status;
+	status = test_membarrier_private_expedited_fail();
+	if (status)
+		return status;
+	status = test_membarrier_register_private_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
 	return 0;
@@ -108,5 +187,5 @@ int main(int argc, char **argv)
 	test_membarrier_query();
 	test_membarrier();
 
-	ksft_exit_pass();
+	return ksft_exit_pass();
 }
-- 
2.11.0

[RFC PATCH v2 for 4.15 15/24] membarrier: selftest: Test private expedited cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED and
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED commands.

Add checks expecting specific error values on system calls expected to
fail.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
Changes since v1:
- return result of ksft_exit_pass from main(), silencing compiler
  warning about missing return value.
---
 .../testing/selftests/membarrier/membarrier_test.c | 111 ++++++++++++++++++---
 1 file changed, 95 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index 9e674d9514d1..e6ee73d01fa1 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -16,49 +16,119 @@ static int sys_membarrier(int cmd, int flags)
 static int test_membarrier_cmd_fail(void)
 {
 	int cmd = -1, flags = 0;
+	const char *test_name = "sys membarrier invalid command";
 
 	if (sys_membarrier(cmd, flags) != -1) {
 		ksft_exit_fail_msg(
-			"sys membarrier invalid command test: command = %d, flags = %d. Should fail, but passed\n",
-			cmd, flags);
+			"%s test: command = %d, flags = %d. Should fail, but passed\n",
+			test_name, cmd, flags);
+	}
+	if (errno != EINVAL) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EINVAL, strerror(EINVAL),
+			errno, strerror(errno));
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier invalid command test: command = %d, flags = %d. Failed as expected\n",
-		cmd, flags);
+		"%s test: command = %d, flags = %d, errno = %d. Failed as expected\n",
+		test_name, cmd, flags, errno);
 	return 0;
 }
 
 static int test_membarrier_flags_fail(void)
 {
 	int cmd = MEMBARRIER_CMD_QUERY, flags = 1;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_QUERY invalid flags";
 
 	if (sys_membarrier(cmd, flags) != -1) {
 		ksft_exit_fail_msg(
-			"sys membarrier MEMBARRIER_CMD_QUERY invalid flags test: flags = %d. Should fail, but passed\n",
-			flags);
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EINVAL) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EINVAL, strerror(EINVAL),
+			errno, strerror(errno));
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier MEMBARRIER_CMD_QUERY invalid flags test: flags = %d. Failed as expected\n",
-		flags);
+		"%s test: flags = %d, errno = %d. Failed as expected\n",
+		test_name, flags, errno);
 	return 0;
 }
 
-static int test_membarrier_success(void)
+static int test_membarrier_shared_success(void)
 {
 	int cmd = MEMBARRIER_CMD_SHARED, flags = 0;
-	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED\n";
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n", test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_fail(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED not registered failure";
+
+	if (sys_membarrier(cmd, flags) != -1) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EPERM) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EPERM, strerror(EPERM),
+			errno, strerror(errno));
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d, errno = %d\n",
+		test_name, flags, errno);
+	return 0;
+}
+
+static int test_membarrier_register_private_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED";
 
 	if (sys_membarrier(cmd, flags) != 0) {
 		ksft_exit_fail_msg(
-			"sys membarrier MEMBARRIER_CMD_SHARED test: flags = %d\n",
-			flags);
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
 	}
 
 	ksft_test_result_pass(
-		"sys membarrier MEMBARRIER_CMD_SHARED test: flags = %d\n",
-		flags);
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
 	return 0;
 }
 
@@ -72,7 +142,16 @@ static int test_membarrier(void)
 	status = test_membarrier_flags_fail();
 	if (status)
 		return status;
-	status = test_membarrier_success();
+	status = test_membarrier_shared_success();
+	if (status)
+		return status;
+	status = test_membarrier_private_expedited_fail();
+	if (status)
+		return status;
+	status = test_membarrier_register_private_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
 	return 0;
@@ -108,5 +187,5 @@ int main(int argc, char **argv)
 	test_membarrier_query();
 	test_membarrier();
 
-	ksft_exit_pass();
+	return ksft_exit_pass();
 }
-- 
2.11.0

[RFC PATCH v7 for 4.15 16/24] membarrier: powerpc: Skip memory barrier in switch_mm()

[Mathieu Desnoyers]

Allow PowerPC to skip the full memory barrier in switch_mm(), and
only issue the barrier when scheduling into a task belonging to a
process that has registered to use expedited private.

Threads targeting the same VM but which belong to different thread
groups is a tricky case. It has a few consequences:

It turns out that we cannot rely on get_nr_threads(p) to count the
number of threads using a VM. We can use
(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)
instead to skip the synchronize_sched() for cases where the VM only has
a single user, and that user only has a single thread.

It also turns out that we cannot use for_each_thread() to set
thread flags in all threads using a VM, as it only iterates on the
thread group.

Therefore, test the membarrier state variable directly rather than
relying on thread flags. This means
membarrier_register_private_expedited() needs to set the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag, issue synchronize_sched(), and
only then set MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY which allows
private expedited membarrier commands to succeed.
membarrier_arch_switch_mm() now tests for the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag.

Changes since v1:
- Use test_ti_thread_flag(next, ...) instead of test_thread_flag() in
  powerpc membarrier_arch_sched_in(), given that we want to specifically
  check the next thread state.
- Add missing ARCH_HAS_MEMBARRIER_HOOKS in Kconfig.
- Use task_thread_info() to pass thread_info from task to
  *_ti_thread_flag().

Changes since v2:
- Move membarrier_arch_sched_in() call to finish_task_switch().
- Check for NULL t->mm in membarrier_arch_fork().
- Use membarrier_sched_in() in generic code, which invokes the
  arch-specific membarrier_arch_sched_in(). This fixes allnoconfig
  build on PowerPC.
- Move asm/membarrier.h include under CONFIG_MEMBARRIER, fixing
  allnoconfig build on PowerPC.
- Build and runtime tested on PowerPC.

Changes since v3:
- Simply rely on copy_mm() to copy the membarrier_private_expedited mm
  field on fork.
- powerpc: test thread flag instead of reading
  membarrier_private_expedited in membarrier_arch_fork().
- powerpc: skip memory barrier in membarrier_arch_sched_in() if coming
  from kernel thread, since mmdrop() implies a full barrier.
- Set membarrier_private_expedited to 1 only after arch registration
  code, thus eliminating a race where concurrent commands could succeed
  when they should fail if issued concurrently with process
  registration.
- Use READ_ONCE() for membarrier_private_expedited field access in
  membarrier_private_expedited. Matches WRITE_ONCE() performed in
  process registration.

Changes since v4:
- Move powerpc hook from sched_in() to switch_mm(), based on feedback
  from Nicholas Piggin.

Changes since v5:
- Rebase on v4.14-rc6.
- Fold "Fix: membarrier: Handle CLONE_VM + !CLONE_THREAD correctly on
  powerpc (v2)"

Changes since v6:
- Rename MEMBARRIER_STATE_SWITCH_MM to MEMBARRIER_STATE_PRIVATE_EXPEDITED.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Ingo Molnar <mingo@redhat.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Nicholas Piggin <npiggin@gmail.com>
CC: linuxppc-dev@lists.ozlabs.org
CC: linux-arch@vger.kernel.org
---
 MAINTAINERS                           |  1 +
 arch/powerpc/Kconfig                  |  1 +
 arch/powerpc/include/asm/membarrier.h | 25 +++++++++++++++++++++++++
 arch/powerpc/mm/mmu_context.c         |  7 +++++++
 include/linux/sched/mm.h              | 12 +++++++++++-
 init/Kconfig                          |  3 +++
 kernel/sched/core.c                   | 10 ----------
 kernel/sched/membarrier.c             |  9 +++++++++
 8 files changed, 57 insertions(+), 11 deletions(-)
 create mode 100644 arch/powerpc/include/asm/membarrier.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d0bf5c5b4267..cf41984201d2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8842,6 +8842,7 @@ L:	linux-kernel@vger.kernel.org
 S:	Supported
 F:	kernel/sched/membarrier.c
 F:	include/uapi/linux/membarrier.h
+F:	arch/powerpc/include/asm/membarrier.h
 
 MEMORY MANAGEMENT
 L:	linux-mm@kvack.org
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 41d1dae3b1b5..e54a822e5fb9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -139,6 +139,7 @@ config PPC
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_MEMBARRIER_HOOKS
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/powerpc/include/asm/membarrier.h b/arch/powerpc/include/asm/membarrier.h
new file mode 100644
index 000000000000..046f96768ab5
--- /dev/null
+++ b/arch/powerpc/include/asm/membarrier.h
@@ -0,0 +1,25 @@
+#ifndef _ASM_POWERPC_MEMBARRIER_H
+#define _ASM_POWERPC_MEMBARRIER_H
+
+static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
+		struct mm_struct *next, struct task_struct *tsk)
+{
+	/*
+	 * Only need the full barrier when switching between processes.
+	 * Barrier when switching from kernel to userspace is not
+	 * required here, given that it is implied by mmdrop(). Barrier
+	 * when switching from userspace to kernel is not needed after
+	 * store to rq->curr.
+	 */
+	if (likely(!(atomic_read(&next->membarrier_state)
+			& MEMBARRIER_STATE_PRIVATE_EXPEDITED) || !prev))
+		return;
+
+	/*
+	 * The membarrier system call requires a full memory barrier
+	 * after storing to rq->curr, before going back to user-space.
+	 */
+	smp_mb();
+}
+
+#endif /* _ASM_POWERPC_MEMBARRIER_H */
diff --git a/arch/powerpc/mm/mmu_context.c b/arch/powerpc/mm/mmu_context.c
index 0f613bc63c50..22f5c91cdc38 100644
--- a/arch/powerpc/mm/mmu_context.c
+++ b/arch/powerpc/mm/mmu_context.c
@@ -12,6 +12,7 @@
 
 #include <linux/mm.h>
 #include <linux/cpu.h>
+#include <linux/sched/mm.h>
 
 #include <asm/mmu_context.h>
 
@@ -67,6 +68,10 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 		 *
 		 * On the read side the barrier is in pte_xchg(), which orders
 		 * the store to the PTE vs the load of mm_cpumask.
+		 *
+		 * This full barrier is needed by membarrier when switching
+		 * between processes after store to rq->curr, before user-space
+		 * memory accesses.
 		 */
 		smp_mb();
 
@@ -89,6 +94,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 
 	if (new_on_cpu)
 		radix_kvm_prefetch_workaround(next);
+	else
+		membarrier_arch_switch_mm(prev, next, tsk);
 
 	/*
 	 * The actual HW switching method differs between the various
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 3d49b91b674d..7077253d0df4 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -215,14 +215,24 @@ static inline void memalloc_noreclaim_restore(unsigned int flags)
 #ifdef CONFIG_MEMBARRIER
 enum {
 	MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY	= (1U << 0),
-	MEMBARRIER_STATE_SWITCH_MM			= (1U << 1),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED		= (1U << 1),
 };
 
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
+#include <asm/membarrier.h>
+#endif
+
 static inline void membarrier_execve(struct task_struct *t)
 {
 	atomic_set(&t->mm->membarrier_state, 0);
 }
 #else
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
+static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
+		struct mm_struct *next, struct task_struct *tsk)
+{
+}
+#endif
 static inline void membarrier_execve(struct task_struct *t)
 {
 }
diff --git a/init/Kconfig b/init/Kconfig
index e4fbb5dd6a24..609296e764d6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1400,6 +1400,9 @@ config MEMBARRIER
 
 	  If unsure, say Y.
 
+config ARCH_HAS_MEMBARRIER_HOOKS
+	bool
+
 config RSEQ
 	bool "Enable rseq() system call" if EXPERT
 	default y
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e547f93a46c2..0ac96e8329d5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2684,16 +2684,6 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 	prev_state = prev->state;
 	vtime_task_switch(prev);
 	perf_event_task_sched_in(prev, current);
-	/*
-	 * The membarrier system call requires a full memory barrier
-	 * after storing to rq->curr, before going back to user-space.
-	 *
-	 * TODO: This smp_mb__after_unlock_lock can go away if PPC end
-	 * up adding a full barrier to switch_mm(), or we should figure
-	 * out if a smp_mb__after_unlock_lock is really the proper API
-	 * to use.
-	 */
-	smp_mb__after_unlock_lock();
 	finish_lock_switch(rq, prev);
 	finish_arch_post_lock_switch();
 
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index dd7908743dab..b045974346d0 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -116,6 +116,15 @@ static void membarrier_register_private_expedited(void)
 	if (atomic_read(&mm->membarrier_state)
 			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)
 		return;
+	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
+			&mm->membarrier_state);
+	if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
+		/*
+		 * Ensure all future scheduler executions will observe the
+		 * new thread flag state for this process.
+		 */
+		synchronize_sched();
+	}
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY,
 			&mm->membarrier_state);
 }
-- 
2.11.0

[RFC PATCH v7 for 4.15 16/24] membarrier: powerpc: Skip memory barrier in switch_mm()

[Mathieu Desnoyers]

Allow PowerPC to skip the full memory barrier in switch_mm(), and
only issue the barrier when scheduling into a task belonging to a
process that has registered to use expedited private.

Threads targeting the same VM but which belong to different thread
groups is a tricky case. It has a few consequences:

It turns out that we cannot rely on get_nr_threads(p) to count the
number of threads using a VM. We can use
(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)
instead to skip the synchronize_sched() for cases where the VM only has
a single user, and that user only has a single thread.

It also turns out that we cannot use for_each_thread() to set
thread flags in all threads using a VM, as it only iterates on the
thread group.

Therefore, test the membarrier state variable directly rather than
relying on thread flags. This means
membarrier_register_private_expedited() needs to set the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag, issue synchronize_sched(), and
only then set MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY which allows
private expedited membarrier commands to succeed.
membarrier_arch_switch_mm() now tests for the
MEMBARRIER_STATE_PRIVATE_EXPEDITED flag.

Changes since v1:
- Use test_ti_thread_flag(next, ...) instead of test_thread_flag() in
  powerpc membarrier_arch_sched_in(), given that we want to specifically
  check the next thread state.
- Add missing ARCH_HAS_MEMBARRIER_HOOKS in Kconfig.
- Use task_thread_info() to pass thread_info from task to
  *_ti_thread_flag().

Changes since v2:
- Move membarrier_arch_sched_in() call to finish_task_switch().
- Check for NULL t->mm in membarrier_arch_fork().
- Use membarrier_sched_in() in generic code, which invokes the
  arch-specific membarrier_arch_sched_in(). This fixes allnoconfig
  build on PowerPC.
- Move asm/membarrier.h include under CONFIG_MEMBARRIER, fixing
  allnoconfig build on PowerPC.
- Build and runtime tested on PowerPC.

Changes since v3:
- Simply rely on copy_mm() to copy the membarrier_private_expedited mm
  field on fork.
- powerpc: test thread flag instead of reading
  membarrier_private_expedited in membarrier_arch_fork().
- powerpc: skip memory barrier in membarrier_arch_sched_in() if coming
  from kernel thread, since mmdrop() implies a full barrier.
- Set membarrier_private_expedited to 1 only after arch registration
  code, thus eliminating a race where concurrent commands could succeed
  when they should fail if issued concurrently with process
  registration.
- Use READ_ONCE() for membarrier_private_expedited field access in
  membarrier_private_expedited. Matches WRITE_ONCE() performed in
  process registration.

Changes since v4:
- Move powerpc hook from sched_in() to switch_mm(), based on feedback
  from Nicholas Piggin.

Changes since v5:
- Rebase on v4.14-rc6.
- Fold "Fix: membarrier: Handle CLONE_VM + !CLONE_THREAD correctly on
  powerpc (v2)"

Changes since v6:
- Rename MEMBARRIER_STATE_SWITCH_MM to MEMBARRIER_STATE_PRIVATE_EXPEDITED.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Ingo Molnar <mingo@redhat.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Nicholas Piggin <npiggin@gmail.com>
CC: linuxppc-dev@lists.ozlabs.org
CC: linux-arch@vger.kernel.org
---
 MAINTAINERS                           |  1 +
 arch/powerpc/Kconfig                  |  1 +
 arch/powerpc/include/asm/membarrier.h | 25 +++++++++++++++++++++++++
 arch/powerpc/mm/mmu_context.c         |  7 +++++++
 include/linux/sched/mm.h              | 12 +++++++++++-
 init/Kconfig                          |  3 +++
 kernel/sched/core.c                   | 10 ----------
 kernel/sched/membarrier.c             |  9 +++++++++
 8 files changed, 57 insertions(+), 11 deletions(-)
 create mode 100644 arch/powerpc/include/asm/membarrier.h

diff --git a/MAINTAINERS b/MAINTAINERS
index d0bf5c5b4267..cf41984201d2 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8842,6 +8842,7 @@ L:	linux-kernel@vger.kernel.org
 S:	Supported
 F:	kernel/sched/membarrier.c
 F:	include/uapi/linux/membarrier.h
+F:	arch/powerpc/include/asm/membarrier.h
 
 MEMORY MANAGEMENT
 L:	linux-mm@kvack.org
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 41d1dae3b1b5..e54a822e5fb9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -139,6 +139,7 @@ config PPC
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_MEMBARRIER_HOOKS
 	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
diff --git a/arch/powerpc/include/asm/membarrier.h b/arch/powerpc/include/asm/membarrier.h
new file mode 100644
index 000000000000..046f96768ab5
--- /dev/null
+++ b/arch/powerpc/include/asm/membarrier.h
@@ -0,0 +1,25 @@
+#ifndef _ASM_POWERPC_MEMBARRIER_H
+#define _ASM_POWERPC_MEMBARRIER_H
+
+static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
+		struct mm_struct *next, struct task_struct *tsk)
+{
+	/*
+	 * Only need the full barrier when switching between processes.
+	 * Barrier when switching from kernel to userspace is not
+	 * required here, given that it is implied by mmdrop(). Barrier
+	 * when switching from userspace to kernel is not needed after
+	 * store to rq->curr.
+	 */
+	if (likely(!(atomic_read(&next->membarrier_state)
+			& MEMBARRIER_STATE_PRIVATE_EXPEDITED) || !prev))
+		return;
+
+	/*
+	 * The membarrier system call requires a full memory barrier
+	 * after storing to rq->curr, before going back to user-space.
+	 */
+	smp_mb();
+}
+
+#endif /* _ASM_POWERPC_MEMBARRIER_H */
diff --git a/arch/powerpc/mm/mmu_context.c b/arch/powerpc/mm/mmu_context.c
index 0f613bc63c50..22f5c91cdc38 100644
--- a/arch/powerpc/mm/mmu_context.c
+++ b/arch/powerpc/mm/mmu_context.c
@@ -12,6 +12,7 @@
 
 #include <linux/mm.h>
 #include <linux/cpu.h>
+#include <linux/sched/mm.h>
 
 #include <asm/mmu_context.h>
 
@@ -67,6 +68,10 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 		 *
 		 * On the read side the barrier is in pte_xchg(), which orders
 		 * the store to the PTE vs the load of mm_cpumask.
+		 *
+		 * This full barrier is needed by membarrier when switching
+		 * between processes after store to rq->curr, before user-space
+		 * memory accesses.
 		 */
 		smp_mb();
 
@@ -89,6 +94,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 
 	if (new_on_cpu)
 		radix_kvm_prefetch_workaround(next);
+	else
+		membarrier_arch_switch_mm(prev, next, tsk);
 
 	/*
 	 * The actual HW switching method differs between the various
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 3d49b91b674d..7077253d0df4 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -215,14 +215,24 @@ static inline void memalloc_noreclaim_restore(unsigned int flags)
 #ifdef CONFIG_MEMBARRIER
 enum {
 	MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY	= (1U << 0),
-	MEMBARRIER_STATE_SWITCH_MM			= (1U << 1),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED		= (1U << 1),
 };
 
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
+#include <asm/membarrier.h>
+#endif
+
 static inline void membarrier_execve(struct task_struct *t)
 {
 	atomic_set(&t->mm->membarrier_state, 0);
 }
 #else
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
+static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
+		struct mm_struct *next, struct task_struct *tsk)
+{
+}
+#endif
 static inline void membarrier_execve(struct task_struct *t)
 {
 }
diff --git a/init/Kconfig b/init/Kconfig
index e4fbb5dd6a24..609296e764d6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1400,6 +1400,9 @@ config MEMBARRIER
 
 	  If unsure, say Y.
 
+config ARCH_HAS_MEMBARRIER_HOOKS
+	bool
+
 config RSEQ
 	bool "Enable rseq() system call" if EXPERT
 	default y
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e547f93a46c2..0ac96e8329d5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2684,16 +2684,6 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 	prev_state = prev->state;
 	vtime_task_switch(prev);
 	perf_event_task_sched_in(prev, current);
-	/*
-	 * The membarrier system call requires a full memory barrier
-	 * after storing to rq->curr, before going back to user-space.
-	 *
-	 * TODO: This smp_mb__after_unlock_lock can go away if PPC end
-	 * up adding a full barrier to switch_mm(), or we should figure
-	 * out if a smp_mb__after_unlock_lock is really the proper API
-	 * to use.
-	 */
-	smp_mb__after_unlock_lock();
 	finish_lock_switch(rq, prev);
 	finish_arch_post_lock_switch();
 
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index dd7908743dab..b045974346d0 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -116,6 +116,15 @@ static void membarrier_register_private_expedited(void)
 	if (atomic_read(&mm->membarrier_state)
 			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)
 		return;
+	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
+			&mm->membarrier_state);
+	if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
+		/*
+		 * Ensure all future scheduler executions will observe the
+		 * new thread flag state for this process.
+		 */
+		synchronize_sched();
+	}
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY,
 			&mm->membarrier_state);
 }
-- 
2.11.0

[RFC PATCH for 4.15 19/24] membarrier: selftest: Test shared expedited cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_SHARED_EXPEDITED and
MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED commands.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Shuah Khan <shuahkh@osg.samsung.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
 .../testing/selftests/membarrier/membarrier_test.c | 51 +++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index e6ee73d01fa1..bb9c58072c5c 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -132,6 +132,40 @@ static int test_membarrier_private_expedited_success(void)
 	return 0;
 }
 
+static int test_membarrier_register_shared_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_shared_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_SHARED_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
 static int test_membarrier(void)
 {
 	int status;
@@ -154,6 +188,19 @@ static int test_membarrier(void)
 	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
+	/*
+	 * It is valid to send a shared membarrier from a non-registered
+	 * process.
+	 */
+	status = test_membarrier_shared_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_register_shared_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_shared_expedited_success();
+	if (status)
+		return status;
 	return 0;
 }
 
@@ -173,8 +220,10 @@ static int test_membarrier_query(void)
 		}
 		ksft_exit_fail_msg("sys_membarrier() failed\n");
 	}
-	if (!(ret & MEMBARRIER_CMD_SHARED))
+	if (!(ret & MEMBARRIER_CMD_SHARED)) {
+		ksft_test_result_fail("sys_membarrier() CMD_SHARED query failed\n");
 		ksft_exit_fail_msg("sys_membarrier is not supported.\n");
+	}
 
 	ksft_test_result_pass("sys_membarrier available\n");
 	return 0;
-- 
2.11.0

[RFC PATCH for 4.15 19/24] membarrier: selftest: Test shared expedited cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_SHARED_EXPEDITED and
MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED commands.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Shuah Khan <shuahkh@osg.samsung.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
 .../testing/selftests/membarrier/membarrier_test.c | 51 +++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index e6ee73d01fa1..bb9c58072c5c 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -132,6 +132,40 @@ static int test_membarrier_private_expedited_success(void)
 	return 0;
 }
 
+static int test_membarrier_register_shared_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_shared_expedited_success(void)
+{
+	int cmd = MEMBARRIER_CMD_SHARED_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED_EXPEDITED";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
 static int test_membarrier(void)
 {
 	int status;
@@ -154,6 +188,19 @@ static int test_membarrier(void)
 	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
+	/*
+	 * It is valid to send a shared membarrier from a non-registered
+	 * process.
+	 */
+	status = test_membarrier_shared_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_register_shared_expedited_success();
+	if (status)
+		return status;
+	status = test_membarrier_shared_expedited_success();
+	if (status)
+		return status;
 	return 0;
 }
 
@@ -173,8 +220,10 @@ static int test_membarrier_query(void)
 		}
 		ksft_exit_fail_msg("sys_membarrier() failed\n");
 	}
-	if (!(ret & MEMBARRIER_CMD_SHARED))
+	if (!(ret & MEMBARRIER_CMD_SHARED)) {
+		ksft_test_result_fail("sys_membarrier() CMD_SHARED query failed\n");
 		ksft_exit_fail_msg("sys_membarrier is not supported.\n");
+	}
 
 	ksft_test_result_pass("sys_membarrier available\n");
 	return 0;
-- 
2.11.0

Re: [RFC PATCH for 4.15 19/24] membarrier: selftest: Test shared expedited cmd

[Shuah Khan]

On 11/14/2017 01:04 PM, Mathieu Desnoyers wrote:
> Test the new MEMBARRIER_CMD_SHARED_EXPEDITED and
> MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED commands.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
> CC: Shuah Khan <shuahkh-JPH+aEBZ4P+UEJcrhfAQsw@public.gmane.org>
> CC: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
> CC: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
> CC: Paul E. McKenney <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> CC: Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> CC: Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> CC: Maged Michael <maged.michael-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> CC: Avi Kivity <avi-VrcmuVmyx1hWk0Htik3J/w@public.gmane.org>
> CC: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
> CC: Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> CC: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
> CC: Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>
> CC: Alan Stern <stern-nwvwT67g6+6dFdvTe/nMLpVzexx5G7lz@public.gmane.org>
> CC: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
> CC: Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> CC: Alice Ferrazzi <alice.ferrazzi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> CC: Paul Elder <paul.elder-fYq5UfK3d1k@public.gmane.org>
> CC: linux-kselftest-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> CC: linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> ---
>  .../testing/selftests/membarrier/membarrier_test.c | 51 +++++++++++++++++++++-
>  1 file changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
> index e6ee73d01fa1..bb9c58072c5c 100644
> --- a/tools/testing/selftests/membarrier/membarrier_test.c
> +++ b/tools/testing/selftests/membarrier/membarrier_test.c
> @@ -132,6 +132,40 @@ static int test_membarrier_private_expedited_success(void)
>  	return 0;
>  }
>  
> +static int test_membarrier_register_shared_expedited_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
> +static int test_membarrier_shared_expedited_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_SHARED_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED_EXPEDITED";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
>  static int test_membarrier(void)
>  {
>  	int status;
> @@ -154,6 +188,19 @@ static int test_membarrier(void)
>  	status = test_membarrier_private_expedited_success();
>  	if (status)
>  		return status;
> +	/*
> +	 * It is valid to send a shared membarrier from a non-registered
> +	 * process.
> +	 */
> +	status = test_membarrier_shared_expedited_success();
> +	if (status)
> +		return status;
> +	status = test_membarrier_register_shared_expedited_success();
> +	if (status)
> +		return status;
> +	status = test_membarrier_shared_expedited_success();
> +	if (status)
> +		return status;
>  	return 0;
>  }
>  
> @@ -173,8 +220,10 @@ static int test_membarrier_query(void)
>  		}
>  		ksft_exit_fail_msg("sys_membarrier() failed\n");
>  	}
> -	if (!(ret & MEMBARRIER_CMD_SHARED))
> +	if (!(ret & MEMBARRIER_CMD_SHARED)) {
> +		ksft_test_result_fail("sys_membarrier() CMD_SHARED query failed\n");
>  		ksft_exit_fail_msg("sys_membarrier is not supported.\n");
> +	}
>  
>  	ksft_test_result_pass("sys_membarrier available\n");
>  	return 0;
> 

Looks good to me. I am assuming this patch goes in with the rest of the
series. For this patch:

Acked-by: Shuah Khan <shuahkh-JPH+aEBZ4P+UEJcrhfAQsw@public.gmane.org>

thanks,
-- Shuah

Re: [RFC PATCH for 4.15 19/24] membarrier: selftest: Test shared expedited cmd

[Shuah Khan]

On 11/14/2017 01:04 PM, Mathieu Desnoyers wrote:
> Test the new MEMBARRIER_CMD_SHARED_EXPEDITED and
> MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED commands.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> CC: Shuah Khan <shuahkh@osg.samsung.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Andy Lutomirski <luto@kernel.org>
> CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
> CC: Paul Elder <paul.elder@pitt.edu>
> CC: linux-kselftest@vger.kernel.org
> CC: linux-arch@vger.kernel.org
> ---
>  .../testing/selftests/membarrier/membarrier_test.c | 51 +++++++++++++++++++++-
>  1 file changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
> index e6ee73d01fa1..bb9c58072c5c 100644
> --- a/tools/testing/selftests/membarrier/membarrier_test.c
> +++ b/tools/testing/selftests/membarrier/membarrier_test.c
> @@ -132,6 +132,40 @@ static int test_membarrier_private_expedited_success(void)
>  	return 0;
>  }
>  
> +static int test_membarrier_register_shared_expedited_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
> +static int test_membarrier_shared_expedited_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_SHARED_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_SHARED_EXPEDITED";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
>  static int test_membarrier(void)
>  {
>  	int status;
> @@ -154,6 +188,19 @@ static int test_membarrier(void)
>  	status = test_membarrier_private_expedited_success();
>  	if (status)
>  		return status;
> +	/*
> +	 * It is valid to send a shared membarrier from a non-registered
> +	 * process.
> +	 */
> +	status = test_membarrier_shared_expedited_success();
> +	if (status)
> +		return status;
> +	status = test_membarrier_register_shared_expedited_success();
> +	if (status)
> +		return status;
> +	status = test_membarrier_shared_expedited_success();
> +	if (status)
> +		return status;
>  	return 0;
>  }
>  
> @@ -173,8 +220,10 @@ static int test_membarrier_query(void)
>  		}
>  		ksft_exit_fail_msg("sys_membarrier() failed\n");
>  	}
> -	if (!(ret & MEMBARRIER_CMD_SHARED))
> +	if (!(ret & MEMBARRIER_CMD_SHARED)) {
> +		ksft_test_result_fail("sys_membarrier() CMD_SHARED query failed\n");
>  		ksft_exit_fail_msg("sys_membarrier is not supported.\n");
> +	}
>  
>  	ksft_test_result_pass("sys_membarrier available\n");
>  	return 0;
> 

Looks good to me. I am assuming this patch goes in with the rest of the
series. For this patch:

Acked-by: Shuah Khan <shuahkh@osg.samsung.com>

thanks,
-- Shuah

[RFC PATCH for 4.15 20/24] membarrier: Provide core serializing command

[Mathieu Desnoyers]

Provide core serializing membarrier command to support memory reclaim
by JIT.

Each architecture needs to explicitly opt into that support by
documenting in their architecture code how they provide the core
serializing instructions required when returning from the membarrier
IPI, and after the scheduler has updated the curr->mm pointer (before
going back to user-space). They should then select
ARCH_HAS_MEMBARRIER_SYNC_CORE to enable support for that command on
their architecture.

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: linux-arch@vger.kernel.org
---
 include/linux/sched/mm.h        |  6 +++++
 include/uapi/linux/membarrier.h | 32 +++++++++++++++++++++++++-
 init/Kconfig                    |  3 +++
 kernel/sched/membarrier.c       | 50 +++++++++++++++++++++++++++++++----------
 4 files changed, 78 insertions(+), 13 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index c7b0f5970d7c..b7abb7de250f 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -223,6 +223,12 @@ enum {
 	MEMBARRIER_STATE_PRIVATE_EXPEDITED			= (1U << 1),
 	MEMBARRIER_STATE_SHARED_EXPEDITED_READY			= (1U << 2),
 	MEMBARRIER_STATE_SHARED_EXPEDITED			= (1U << 3),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY	= (1U << 4),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE		= (1U << 5),
+};
+
+enum {
+	MEMBARRIER_FLAG_SYNC_CORE	= (1U << 0),
 };
 
 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h
index 2de01e595d3b..99a66577bd85 100644
--- a/include/uapi/linux/membarrier.h
+++ b/include/uapi/linux/membarrier.h
@@ -73,7 +73,7 @@
  *                          to and return from the system call
  *                          (non-running threads are de facto in such a
  *                          state). This only covers threads from the
- *                          same processes as the caller thread. This
+ *                          same process as the caller thread. This
  *                          command returns 0 on success. The
  *                          "expedited" commands complete faster than
  *                          the non-expedited ones, they never block,
@@ -86,6 +86,34 @@
  *                          Register the process intent to use
  *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always
  *                          returns 0.
+ * @MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+ *                          In addition to provide memory ordering
+ *                          guarantees described in
+ *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED, ensure
+ *                          the caller thread, upon return from system
+ *                          call, that all its running threads siblings
+ *                          have executed a core serializing
+ *                          instruction. (architectures are required to
+ *                          guarantee that non-running threads issue
+ *                          core serializing instructions before they
+ *                          resume user-space execution). This only
+ *                          covers threads from the same process as the
+ *                          caller thread. This command returns 0 on
+ *                          success. The "expedited" commands complete
+ *                          faster than the non-expedited ones, they
+ *                          never block, but have the downside of
+ *                          causing extra overhead. If this command is
+ *                          not implemented by an architecture, -EINVAL
+ *                          is returned. A process needs to register its
+ *                          intent to use the private expedited sync
+ *                          core command prior to using it, otherwise
+ *                          this command returns -EPERM.
+ * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+ *                          Register the process intent to use
+ *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE.
+ *                          If this command is not implemented by an
+ *                          architecture, -EINVAL is returned.
+ *                          Returns 0 on success.
  *
  * Command to be passed to the membarrier system call. The commands need to
  * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to
@@ -98,6 +126,8 @@ enum membarrier_cmd {
 	MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED		= (1 << 2),
 	MEMBARRIER_CMD_PRIVATE_EXPEDITED			= (1 << 3),
 	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED		= (1 << 4),
+	MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE		= (1 << 5),
+	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE	= (1 << 6),
 };
 
 #endif /* _UAPI_LINUX_MEMBARRIER_H */
diff --git a/init/Kconfig b/init/Kconfig
index 609296e764d6..d3e5440051b8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1403,6 +1403,9 @@ config MEMBARRIER
 config ARCH_HAS_MEMBARRIER_HOOKS
 	bool
 
+config ARCH_HAS_MEMBARRIER_SYNC_CORE
+	bool
+
 config RSEQ
 	bool "Enable rseq() system call" if EXPERT
 	default y
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 76534531098f..72f42eac99ab 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -26,11 +26,20 @@
  * Bitmask made from a "or" of all commands within enum membarrier_cmd,
  * except MEMBARRIER_CMD_QUERY.
  */
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	\
+	(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE \
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE)
+#else
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	0
+#endif
+
 #define MEMBARRIER_CMD_BITMASK	\
 	(MEMBARRIER_CMD_SHARED | MEMBARRIER_CMD_SHARED_EXPEDITED \
 	| MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED \
 	| MEMBARRIER_CMD_PRIVATE_EXPEDITED	\
-	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED)
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED	\
+	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)
 
 static void ipi_mb(void *info)
 {
@@ -102,15 +111,23 @@ static int membarrier_shared_expedited(void)
 	return 0;
 }
 
-static int membarrier_private_expedited(void)
+static int membarrier_private_expedited(int flags)
 {
 	int cpu;
 	bool fallback = false;
 	cpumask_var_t tmpmask;
 
-	if (!(atomic_read(&current->mm->membarrier_state)
-			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
-		return -EPERM;
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+			return -EINVAL;
+		if (!(atomic_read(&current->mm->membarrier_state)
+				& MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY))
+			return -EPERM;
+	} else {
+		if (!(atomic_read(&current->mm->membarrier_state)
+				& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
+			return -EPERM;
+	}
 
 	if (num_online_cpus() == 1)
 		return 0;
@@ -201,18 +218,24 @@ static int membarrier_register_shared_expedited(void)
 	return 0;
 }
 
-static int membarrier_register_private_expedited(void)
+static int membarrier_register_private_expedited(int flags)
 {
 	struct task_struct *p = current;
 	struct mm_struct *mm = p->mm;
+	int state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY;
+
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+			return -EINVAL;
+		state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY;
+	}
 
 	/*
 	 * We need to consider threads belonging to different thread
 	 * groups, which use the same mm. (CLONE_VM but not
 	 * CLONE_THREAD).
 	 */
-	if (atomic_read(&mm->membarrier_state)
-			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)
+	if (atomic_read(&mm->membarrier_state) & state)
 		return 0;
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
 			&mm->membarrier_state);
@@ -223,8 +246,7 @@ static int membarrier_register_private_expedited(void)
 		 */
 		synchronize_sched();
 	}
-	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY,
-			&mm->membarrier_state);
+	atomic_or(state, &mm->membarrier_state);
 	return 0;
 }
 
@@ -280,9 +302,13 @@ SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
 	case MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED:
 		return membarrier_register_shared_expedited();
 	case MEMBARRIER_CMD_PRIVATE_EXPEDITED:
-		return membarrier_private_expedited();
+		return membarrier_private_expedited(0);
 	case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
-		return membarrier_register_private_expedited();
+		return membarrier_register_private_expedited(0);
+	case MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+		return membarrier_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
+	case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+		return membarrier_register_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
 	default:
 		return -EINVAL;
 	}
-- 
2.11.0

[RFC PATCH for 4.15 20/24] membarrier: Provide core serializing command

[Mathieu Desnoyers]

Provide core serializing membarrier command to support memory reclaim
by JIT.

Each architecture needs to explicitly opt into that support by
documenting in their architecture code how they provide the core
serializing instructions required when returning from the membarrier
IPI, and after the scheduler has updated the curr->mm pointer (before
going back to user-space). They should then select
ARCH_HAS_MEMBARRIER_SYNC_CORE to enable support for that command on
their architecture.

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: linux-arch@vger.kernel.org
---
 include/linux/sched/mm.h        |  6 +++++
 include/uapi/linux/membarrier.h | 32 +++++++++++++++++++++++++-
 init/Kconfig                    |  3 +++
 kernel/sched/membarrier.c       | 50 +++++++++++++++++++++++++++++++----------
 4 files changed, 78 insertions(+), 13 deletions(-)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index c7b0f5970d7c..b7abb7de250f 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -223,6 +223,12 @@ enum {
 	MEMBARRIER_STATE_PRIVATE_EXPEDITED			= (1U << 1),
 	MEMBARRIER_STATE_SHARED_EXPEDITED_READY			= (1U << 2),
 	MEMBARRIER_STATE_SHARED_EXPEDITED			= (1U << 3),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY	= (1U << 4),
+	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE		= (1U << 5),
+};
+
+enum {
+	MEMBARRIER_FLAG_SYNC_CORE	= (1U << 0),
 };
 
 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h
index 2de01e595d3b..99a66577bd85 100644
--- a/include/uapi/linux/membarrier.h
+++ b/include/uapi/linux/membarrier.h
@@ -73,7 +73,7 @@
  *                          to and return from the system call
  *                          (non-running threads are de facto in such a
  *                          state). This only covers threads from the
- *                          same processes as the caller thread. This
+ *                          same process as the caller thread. This
  *                          command returns 0 on success. The
  *                          "expedited" commands complete faster than
  *                          the non-expedited ones, they never block,
@@ -86,6 +86,34 @@
  *                          Register the process intent to use
  *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always
  *                          returns 0.
+ * @MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+ *                          In addition to provide memory ordering
+ *                          guarantees described in
+ *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED, ensure
+ *                          the caller thread, upon return from system
+ *                          call, that all its running threads siblings
+ *                          have executed a core serializing
+ *                          instruction. (architectures are required to
+ *                          guarantee that non-running threads issue
+ *                          core serializing instructions before they
+ *                          resume user-space execution). This only
+ *                          covers threads from the same process as the
+ *                          caller thread. This command returns 0 on
+ *                          success. The "expedited" commands complete
+ *                          faster than the non-expedited ones, they
+ *                          never block, but have the downside of
+ *                          causing extra overhead. If this command is
+ *                          not implemented by an architecture, -EINVAL
+ *                          is returned. A process needs to register its
+ *                          intent to use the private expedited sync
+ *                          core command prior to using it, otherwise
+ *                          this command returns -EPERM.
+ * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+ *                          Register the process intent to use
+ *                          MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE.
+ *                          If this command is not implemented by an
+ *                          architecture, -EINVAL is returned.
+ *                          Returns 0 on success.
  *
  * Command to be passed to the membarrier system call. The commands need to
  * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to
@@ -98,6 +126,8 @@ enum membarrier_cmd {
 	MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED		= (1 << 2),
 	MEMBARRIER_CMD_PRIVATE_EXPEDITED			= (1 << 3),
 	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED		= (1 << 4),
+	MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE		= (1 << 5),
+	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE	= (1 << 6),
 };
 
 #endif /* _UAPI_LINUX_MEMBARRIER_H */
diff --git a/init/Kconfig b/init/Kconfig
index 609296e764d6..d3e5440051b8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1403,6 +1403,9 @@ config MEMBARRIER
 config ARCH_HAS_MEMBARRIER_HOOKS
 	bool
 
+config ARCH_HAS_MEMBARRIER_SYNC_CORE
+	bool
+
 config RSEQ
 	bool "Enable rseq() system call" if EXPERT
 	default y
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 76534531098f..72f42eac99ab 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -26,11 +26,20 @@
  * Bitmask made from a "or" of all commands within enum membarrier_cmd,
  * except MEMBARRIER_CMD_QUERY.
  */
+#ifdef CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	\
+	(MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE \
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE)
+#else
+#define MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK	0
+#endif
+
 #define MEMBARRIER_CMD_BITMASK	\
 	(MEMBARRIER_CMD_SHARED | MEMBARRIER_CMD_SHARED_EXPEDITED \
 	| MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED \
 	| MEMBARRIER_CMD_PRIVATE_EXPEDITED	\
-	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED)
+	| MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED	\
+	| MEMBARRIER_PRIVATE_EXPEDITED_SYNC_CORE_BITMASK)
 
 static void ipi_mb(void *info)
 {
@@ -102,15 +111,23 @@ static int membarrier_shared_expedited(void)
 	return 0;
 }
 
-static int membarrier_private_expedited(void)
+static int membarrier_private_expedited(int flags)
 {
 	int cpu;
 	bool fallback = false;
 	cpumask_var_t tmpmask;
 
-	if (!(atomic_read(&current->mm->membarrier_state)
-			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
-		return -EPERM;
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+			return -EINVAL;
+		if (!(atomic_read(&current->mm->membarrier_state)
+				& MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY))
+			return -EPERM;
+	} else {
+		if (!(atomic_read(&current->mm->membarrier_state)
+				& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY))
+			return -EPERM;
+	}
 
 	if (num_online_cpus() == 1)
 		return 0;
@@ -201,18 +218,24 @@ static int membarrier_register_shared_expedited(void)
 	return 0;
 }
 
-static int membarrier_register_private_expedited(void)
+static int membarrier_register_private_expedited(int flags)
 {
 	struct task_struct *p = current;
 	struct mm_struct *mm = p->mm;
+	int state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY;
+
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE))
+			return -EINVAL;
+		state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY;
+	}
 
 	/*
 	 * We need to consider threads belonging to different thread
 	 * groups, which use the same mm. (CLONE_VM but not
 	 * CLONE_THREAD).
 	 */
-	if (atomic_read(&mm->membarrier_state)
-			& MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)
+	if (atomic_read(&mm->membarrier_state) & state)
 		return 0;
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
 			&mm->membarrier_state);
@@ -223,8 +246,7 @@ static int membarrier_register_private_expedited(void)
 		 */
 		synchronize_sched();
 	}
-	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY,
-			&mm->membarrier_state);
+	atomic_or(state, &mm->membarrier_state);
 	return 0;
 }
 
@@ -280,9 +302,13 @@ SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
 	case MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED:
 		return membarrier_register_shared_expedited();
 	case MEMBARRIER_CMD_PRIVATE_EXPEDITED:
-		return membarrier_private_expedited();
+		return membarrier_private_expedited(0);
 	case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
-		return membarrier_register_private_expedited();
+		return membarrier_register_private_expedited(0);
+	case MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE:
+		return membarrier_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
+	case MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+		return membarrier_register_private_expedited(MEMBARRIER_FLAG_SYNC_CORE);
 	default:
 		return -EINVAL;
 	}
-- 
2.11.0

[RFC PATCH v2 for 4.15 21/24] x86: Introduce sync_core_before_usermode

[Mathieu Desnoyers]

Introduce an architecture function that ensures the current CPU
issues a core serializing instruction before returning to usermode.

This is needed for the membarrier "sync_core" command.

Architectures defining the sync_core_before_usermode() static inline
need to select 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
---
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.
---
 arch/x86/Kconfig                 |  1 +
 arch/x86/include/asm/processor.h | 10 ++++++++++
 include/linux/processor.h        |  6 ++++++
 init/Kconfig                     |  3 +++
 kernel/sched/core.c              |  1 +
 5 files changed, 21 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..e47a98a33c2e 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,
+ * sysrel, 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..866de5326d34 100644
--- a/include/linux/processor.h
+++ b/include/linux/processor.h
@@ -68,4 +68,10 @@ do {								\
 
 #endif
 
+#ifndef CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
+static inline void sync_core_before_usermode(void)
+{
+}
+#endif
+
 #endif /* _LINUX_PROCESSOR_H */
diff --git a/init/Kconfig b/init/Kconfig
index d3e5440051b8..ab073d436a9a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1943,3 +1943,6 @@ config ASN1
 	  functions to call on what tags.
 
 source "kernel/Kconfig.locks"
+
+config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
+	bool
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c79e94278613..688b65c68731 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -26,6 +26,7 @@
 #include <linux/profile.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/processor.h>
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
-- 
2.11.0

[RFC PATCH v2 for 4.15 21/24] x86: Introduce sync_core_before_usermode

[Mathieu Desnoyers]

Introduce an architecture function that ensures the current CPU
issues a core serializing instruction before returning to usermode.

This is needed for the membarrier "sync_core" command.

Architectures defining the sync_core_before_usermode() static inline
need to select 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
---
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.
---
 arch/x86/Kconfig                 |  1 +
 arch/x86/include/asm/processor.h | 10 ++++++++++
 include/linux/processor.h        |  6 ++++++
 init/Kconfig                     |  3 +++
 kernel/sched/core.c              |  1 +
 5 files changed, 21 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..e47a98a33c2e 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,
+ * sysrel, 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..866de5326d34 100644
--- a/include/linux/processor.h
+++ b/include/linux/processor.h
@@ -68,4 +68,10 @@ do {								\
 
 #endif
 
+#ifndef CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
+static inline void sync_core_before_usermode(void)
+{
+}
+#endif
+
 #endif /* _LINUX_PROCESSOR_H */
diff --git a/init/Kconfig b/init/Kconfig
index d3e5440051b8..ab073d436a9a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1943,3 +1943,6 @@ config ASN1
 	  functions to call on what tags.
 
 source "kernel/Kconfig.locks"
+
+config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
+	bool
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c79e94278613..688b65c68731 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -26,6 +26,7 @@
 #include <linux/profile.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/processor.h>
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
-- 
2.11.0

[RFC PATCH v2 for 4.15 22/24] membarrier: x86: Provide core serializing command

[Mathieu Desnoyers]

There are two places where core serialization is needed by membarrier:

1) When returning from the membarrier IPI,
2) After scheduler updates curr to a thread with a different mm, before
   going back to user-space, since the curr->mm is used by membarrier to
   check whether it needs to send an IPI to that CPU.

x86-32 uses iret as return from interrupt, and both iret and sysexit to go
back to user-space. The iret instruction is core serializing, but not
sysexit.

x86-64 uses iret as return from interrupt, which takes care of the IPI.
However, it can return to user-space through either sysretl (compat
code), sysretq, or iret. Given that sysret{l,q} is not core serializing,
we rely instead on write_cr3() performed by switch_mm() to provide core
serialization after changing the current mm, and deal with the special
case of kthread -> uthread (temporarily keeping current mm into
active_mm) by adding a sync_core() in that specific case.

Use the new sync_core_before_usermode() to guarantee this.

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: x86@kernel.org
CC: linux-arch@vger.kernel.org

---
Changes since v1:
- Use the newly introduced sync_core_before_usermode(). Move all state
  handling to generic code.
- Add linux/processor.h include to include/linux/sched/mm.h.
---
 arch/x86/Kconfig          |  1 +
 arch/x86/entry/entry_32.S |  5 +++++
 arch/x86/entry/entry_64.S |  8 ++++++++
 arch/x86/mm/tlb.c         |  7 ++++---
 include/linux/sched/mm.h  | 12 ++++++++++++
 kernel/sched/core.c       |  6 +++++-
 kernel/sched/membarrier.c |  4 ++++
 7 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 54fbb8960d94..94bdf5fc7d94 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,7 @@ config X86
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_KCOV			if X86_64
+	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_PMEM_API		if X86_64
 	# Causing hangs/crashes, see the commit that added this change for details.
 	select ARCH_HAS_REFCOUNT		if BROKEN
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 4838037f97f6..04e5daba8456 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -553,6 +553,11 @@ restore_all:
 .Lrestore_nocheck:
 	RESTORE_REGS 4				# skip orig_eax/error_code
 .Lirq_return:
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler and when returning from
+	 * scheduler to user-space.
+	 */
 	INTERRUPT_RETURN
 
 .section .fixup, "ax"
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index bcfc5668dcb2..4859f04e1695 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -642,6 +642,10 @@ GLOBAL(restore_regs_and_iret)
 restore_c_regs_and_iret:
 	RESTORE_C_REGS
 	REMOVE_PT_GPREGS_FROM_STACK 8
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler.
+	 */
 	INTERRUPT_RETURN
 
 ENTRY(native_iret)
@@ -1122,6 +1126,10 @@ paranoid_exit_restore:
 	RESTORE_EXTRA_REGS
 	RESTORE_C_REGS
 	REMOVE_PT_GPREGS_FROM_STACK 8
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler.
+	 */
 	INTERRUPT_RETURN
 END(paranoid_exit)
 
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5abf9bfcca1f..3b13d6735fa5 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -147,9 +147,10 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	this_cpu_write(cpu_tlbstate.is_lazy, false);
 
 	/*
-	 * The membarrier system call requires a full memory barrier
-	 * before returning to user-space, after storing to rq->curr.
-	 * Writing to CR3 provides that full memory barrier.
+	 * The membarrier system call requires a full memory barrier and
+	 * core serialization before returning to user-space, after
+	 * storing to rq->curr. Writing to CR3 provides that full
+	 * memory barrier and core serializing instruction.
 	 */
 	if (real_prev == next) {
 		VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index b7abb7de250f..5b763a73ae43 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -7,6 +7,7 @@
 #include <linux/sched.h>
 #include <linux/mm_types.h>
 #include <linux/gfp.h>
+#include <linux/processor.h>
 
 /*
  * Routines for handling mm_structs
@@ -235,6 +236,14 @@ enum {
 #include <asm/membarrier.h>
 #endif
 
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+	if (likely(!(atomic_read(&mm->membarrier_state) &
+			MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
+		return;
+	sync_core_before_usermode();
+}
+
 static inline void membarrier_execve(struct task_struct *t)
 {
 	atomic_set(&t->mm->membarrier_state, 0);
@@ -249,6 +258,9 @@ static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
 static inline void membarrier_execve(struct task_struct *t)
 {
 }
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+}
 #endif
 
 #endif /* _LINUX_SCHED_MM_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 688b65c68731..43099a091742 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2694,9 +2694,13 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 	 * thread, mmdrop()'s implicit full barrier is required by the
 	 * membarrier system call, because the current active_mm can
 	 * become the current mm without going through switch_mm().
+	 * membarrier also requires a core serializing instruction
+	 * before going back to user-space after storing to rq->curr.
 	 */
-	if (mm)
+	if (mm) {
 		mmdrop(mm);
+		membarrier_mm_sync_core_before_usermode(mm);
+	}
 	if (unlikely(prev_state == TASK_DEAD)) {
 		if (prev->sched_class->task_dead)
 			prev->sched_class->task_dead(prev);
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 72f42eac99ab..d48185974ae0 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -239,6 +239,10 @@ static int membarrier_register_private_expedited(int flags)
 		return 0;
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
 			&mm->membarrier_state);
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE,
+				&mm->membarrier_state);
+	}
 	if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
 		/*
 		 * Ensure all future scheduler executions will observe the
-- 
2.11.0

[RFC PATCH v2 for 4.15 22/24] membarrier: x86: Provide core serializing command

[Mathieu Desnoyers]

There are two places where core serialization is needed by membarrier:

1) When returning from the membarrier IPI,
2) After scheduler updates curr to a thread with a different mm, before
   going back to user-space, since the curr->mm is used by membarrier to
   check whether it needs to send an IPI to that CPU.

x86-32 uses iret as return from interrupt, and both iret and sysexit to go
back to user-space. The iret instruction is core serializing, but not
sysexit.

x86-64 uses iret as return from interrupt, which takes care of the IPI.
However, it can return to user-space through either sysretl (compat
code), sysretq, or iret. Given that sysret{l,q} is not core serializing,
we rely instead on write_cr3() performed by switch_mm() to provide core
serialization after changing the current mm, and deal with the special
case of kthread -> uthread (temporarily keeping current mm into
active_mm) by adding a sync_core() in that specific case.

Use the new sync_core_before_usermode() to guarantee this.

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: x86@kernel.org
CC: linux-arch@vger.kernel.org

---
Changes since v1:
- Use the newly introduced sync_core_before_usermode(). Move all state
  handling to generic code.
- Add linux/processor.h include to include/linux/sched/mm.h.
---
 arch/x86/Kconfig          |  1 +
 arch/x86/entry/entry_32.S |  5 +++++
 arch/x86/entry/entry_64.S |  8 ++++++++
 arch/x86/mm/tlb.c         |  7 ++++---
 include/linux/sched/mm.h  | 12 ++++++++++++
 kernel/sched/core.c       |  6 +++++-
 kernel/sched/membarrier.c |  4 ++++
 7 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 54fbb8960d94..94bdf5fc7d94 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -54,6 +54,7 @@ config X86
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_KCOV			if X86_64
+	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_PMEM_API		if X86_64
 	# Causing hangs/crashes, see the commit that added this change for details.
 	select ARCH_HAS_REFCOUNT		if BROKEN
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 4838037f97f6..04e5daba8456 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -553,6 +553,11 @@ restore_all:
 .Lrestore_nocheck:
 	RESTORE_REGS 4				# skip orig_eax/error_code
 .Lirq_return:
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler and when returning from
+	 * scheduler to user-space.
+	 */
 	INTERRUPT_RETURN
 
 .section .fixup, "ax"
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index bcfc5668dcb2..4859f04e1695 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -642,6 +642,10 @@ GLOBAL(restore_regs_and_iret)
 restore_c_regs_and_iret:
 	RESTORE_C_REGS
 	REMOVE_PT_GPREGS_FROM_STACK 8
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler.
+	 */
 	INTERRUPT_RETURN
 
 ENTRY(native_iret)
@@ -1122,6 +1126,10 @@ paranoid_exit_restore:
 	RESTORE_EXTRA_REGS
 	RESTORE_C_REGS
 	REMOVE_PT_GPREGS_FROM_STACK 8
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on iret core serialization
+	 * when returning from IPI handler.
+	 */
 	INTERRUPT_RETURN
 END(paranoid_exit)
 
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 5abf9bfcca1f..3b13d6735fa5 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -147,9 +147,10 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	this_cpu_write(cpu_tlbstate.is_lazy, false);
 
 	/*
-	 * The membarrier system call requires a full memory barrier
-	 * before returning to user-space, after storing to rq->curr.
-	 * Writing to CR3 provides that full memory barrier.
+	 * The membarrier system call requires a full memory barrier and
+	 * core serialization before returning to user-space, after
+	 * storing to rq->curr. Writing to CR3 provides that full
+	 * memory barrier and core serializing instruction.
 	 */
 	if (real_prev == next) {
 		VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index b7abb7de250f..5b763a73ae43 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -7,6 +7,7 @@
 #include <linux/sched.h>
 #include <linux/mm_types.h>
 #include <linux/gfp.h>
+#include <linux/processor.h>
 
 /*
  * Routines for handling mm_structs
@@ -235,6 +236,14 @@ enum {
 #include <asm/membarrier.h>
 #endif
 
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+	if (likely(!(atomic_read(&mm->membarrier_state) &
+			MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
+		return;
+	sync_core_before_usermode();
+}
+
 static inline void membarrier_execve(struct task_struct *t)
 {
 	atomic_set(&t->mm->membarrier_state, 0);
@@ -249,6 +258,9 @@ static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
 static inline void membarrier_execve(struct task_struct *t)
 {
 }
+static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
+{
+}
 #endif
 
 #endif /* _LINUX_SCHED_MM_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 688b65c68731..43099a091742 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2694,9 +2694,13 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 	 * thread, mmdrop()'s implicit full barrier is required by the
 	 * membarrier system call, because the current active_mm can
 	 * become the current mm without going through switch_mm().
+	 * membarrier also requires a core serializing instruction
+	 * before going back to user-space after storing to rq->curr.
 	 */
-	if (mm)
+	if (mm) {
 		mmdrop(mm);
+		membarrier_mm_sync_core_before_usermode(mm);
+	}
 	if (unlikely(prev_state == TASK_DEAD)) {
 		if (prev->sched_class->task_dead)
 			prev->sched_class->task_dead(prev);
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 72f42eac99ab..d48185974ae0 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -239,6 +239,10 @@ static int membarrier_register_private_expedited(int flags)
 		return 0;
 	atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED,
 			&mm->membarrier_state);
+	if (flags & MEMBARRIER_FLAG_SYNC_CORE) {
+		atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE,
+				&mm->membarrier_state);
+	}
 	if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) {
 		/*
 		 * Ensure all future scheduler executions will observe the
-- 
2.11.0

[RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE and
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE commands.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Shuah Khan <shuahkh@osg.samsung.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
 .../testing/selftests/membarrier/membarrier_test.c | 73 ++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index bb9c58072c5c..d9ab8b6ee52e 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -132,6 +132,63 @@ static int test_membarrier_private_expedited_success(void)
 	return 0;
 }
 
+static int test_membarrier_private_expedited_sync_core_fail(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE not registered failure";
+
+	if (sys_membarrier(cmd, flags) != -1) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EPERM) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EPERM, strerror(EPERM),
+			errno, strerror(errno));
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d, errno = %d\n",
+		test_name, flags, errno);
+	return 0;
+}
+
+static int test_membarrier_register_private_expedited_sync_core_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_sync_core_success(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
 static int test_membarrier_register_shared_expedited_success(void)
 {
 	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
@@ -188,6 +245,22 @@ static int test_membarrier(void)
 	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
+	status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0);
+	if (status < 0) {
+		ksft_test_result_fail("sys_membarrier() failed\n");
+		return status;
+	}
+	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
+		status = test_membarrier_private_expedited_sync_core_fail();
+		if (status)
+			return status;
+		status = test_membarrier_register_private_expedited_sync_core_success();
+		if (status)
+			return status;
+		status = test_membarrier_private_expedited_sync_core_success();
+		if (status)
+			return status;
+	}
 	/*
 	 * It is valid to send a shared membarrier from a non-registered
 	 * process.
-- 
2.11.0

[RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Mathieu Desnoyers]

Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE and
MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE commands.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Shuah Khan <shuahkh@osg.samsung.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
CC: Will Deacon <will.deacon@arm.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
CC: Paul Elder <paul.elder@pitt.edu>
CC: linux-kselftest@vger.kernel.org
CC: linux-arch@vger.kernel.org
---
 .../testing/selftests/membarrier/membarrier_test.c | 73 ++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
index bb9c58072c5c..d9ab8b6ee52e 100644
--- a/tools/testing/selftests/membarrier/membarrier_test.c
+++ b/tools/testing/selftests/membarrier/membarrier_test.c
@@ -132,6 +132,63 @@ static int test_membarrier_private_expedited_success(void)
 	return 0;
 }
 
+static int test_membarrier_private_expedited_sync_core_fail(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE not registered failure";
+
+	if (sys_membarrier(cmd, flags) != -1) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should fail, but passed\n",
+			test_name, flags);
+	}
+	if (errno != EPERM) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
+			test_name, flags, EPERM, strerror(EPERM),
+			errno, strerror(errno));
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d, errno = %d\n",
+		test_name, flags, errno);
+	return 0;
+}
+
+static int test_membarrier_register_private_expedited_sync_core_success(void)
+{
+	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
+static int test_membarrier_private_expedited_sync_core_success(void)
+{
+	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
+	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE";
+
+	if (sys_membarrier(cmd, flags) != 0) {
+		ksft_exit_fail_msg(
+			"%s test: flags = %d, errno = %d\n",
+			test_name, flags, errno);
+	}
+
+	ksft_test_result_pass(
+		"%s test: flags = %d\n",
+		test_name, flags);
+	return 0;
+}
+
 static int test_membarrier_register_shared_expedited_success(void)
 {
 	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
@@ -188,6 +245,22 @@ static int test_membarrier(void)
 	status = test_membarrier_private_expedited_success();
 	if (status)
 		return status;
+	status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0);
+	if (status < 0) {
+		ksft_test_result_fail("sys_membarrier() failed\n");
+		return status;
+	}
+	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
+		status = test_membarrier_private_expedited_sync_core_fail();
+		if (status)
+			return status;
+		status = test_membarrier_register_private_expedited_sync_core_success();
+		if (status)
+			return status;
+		status = test_membarrier_private_expedited_sync_core_success();
+		if (status)
+			return status;
+	}
 	/*
 	 * It is valid to send a shared membarrier from a non-registered
 	 * process.
-- 
2.11.0

Re: [RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Shuah Khan]

On 11/14/2017 01:04 PM, Mathieu Desnoyers wrote:
> Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE and
> MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE commands.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> CC: Shuah Khan <shuahkh@osg.samsung.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Andy Lutomirski <luto@kernel.org>
> CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
> CC: Paul Elder <paul.elder@pitt.edu>
> CC: linux-kselftest@vger.kernel.org
> CC: linux-arch@vger.kernel.org
> ---
>  .../testing/selftests/membarrier/membarrier_test.c | 73 ++++++++++++++++++++++
>  1 file changed, 73 insertions(+)
> 
> diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
> index bb9c58072c5c..d9ab8b6ee52e 100644
> --- a/tools/testing/selftests/membarrier/membarrier_test.c
> +++ b/tools/testing/selftests/membarrier/membarrier_test.c
> @@ -132,6 +132,63 @@ static int test_membarrier_private_expedited_success(void)
>  	return 0;
>  }
>  
> +static int test_membarrier_private_expedited_sync_core_fail(void)
> +{
> +	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE not registered failure";
> +
> +	if (sys_membarrier(cmd, flags) != -1) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d. Should fail, but passed\n",
> +			test_name, flags);
> +	}
> +	if (errno != EPERM) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
> +			test_name, flags, EPERM, strerror(EPERM),
> +			errno, strerror(errno));
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d, errno = %d\n",
> +		test_name, flags, errno);
> +	return 0;
> +}
> +
> +static int test_membarrier_register_private_expedited_sync_core_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
> +static int test_membarrier_private_expedited_sync_core_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
>  static int test_membarrier_register_shared_expedited_success(void)
>  {
>  	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
> @@ -188,6 +245,22 @@ static int test_membarrier(void)
>  	status = test_membarrier_private_expedited_success();
>  	if (status)
>  		return status;
> +	status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0);
> +	if (status < 0) {
> +		ksft_test_result_fail("sys_membarrier() failed\n");
> +		return status;
> +	}
> +	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
> +		status = test_membarrier_private_expedited_sync_core_fail();
> +		if (status)
> +			return status;
> +		status = test_membarrier_register_private_expedited_sync_core_success();
> +		if (status)
> +			return status;
> +		status = test_membarrier_private_expedited_sync_core_success();
> +		if (status)
> +			return status;
> +	}
>  	/*
>  	 * It is valid to send a shared membarrier from a non-registered
>  	 * process.
> 

Looks good to me. I am assuming this patch goes in with the rest of the
series. For this patch:

Acked-by: Shuah Khan <shuahkh@osg.samsung.com>

thanks,
-- Shuah

Re: [RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Shuah Khan]

On 11/14/2017 01:04 PM, Mathieu Desnoyers wrote:
> Test the new MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE and
> MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE commands.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> CC: Shuah Khan <shuahkh@osg.samsung.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: Peter Zijlstra <peterz@infradead.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: Alan Stern <stern@rowland.harvard.edu>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Andy Lutomirski <luto@kernel.org>
> CC: Alice Ferrazzi <alice.ferrazzi@gmail.com>
> CC: Paul Elder <paul.elder@pitt.edu>
> CC: linux-kselftest@vger.kernel.org
> CC: linux-arch@vger.kernel.org
> ---
>  .../testing/selftests/membarrier/membarrier_test.c | 73 ++++++++++++++++++++++
>  1 file changed, 73 insertions(+)
> 
> diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test.c
> index bb9c58072c5c..d9ab8b6ee52e 100644
> --- a/tools/testing/selftests/membarrier/membarrier_test.c
> +++ b/tools/testing/selftests/membarrier/membarrier_test.c
> @@ -132,6 +132,63 @@ static int test_membarrier_private_expedited_success(void)
>  	return 0;
>  }
>  
> +static int test_membarrier_private_expedited_sync_core_fail(void)
> +{
> +	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE not registered failure";
> +
> +	if (sys_membarrier(cmd, flags) != -1) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d. Should fail, but passed\n",
> +			test_name, flags);
> +	}
> +	if (errno != EPERM) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d. Should return (%d: \"%s\"), but returned (%d: \"%s\").\n",
> +			test_name, flags, EPERM, strerror(EPERM),
> +			errno, strerror(errno));
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d, errno = %d\n",
> +		test_name, flags, errno);
> +	return 0;
> +}
> +
> +static int test_membarrier_register_private_expedited_sync_core_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
> +static int test_membarrier_private_expedited_sync_core_success(void)
> +{
> +	int cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED, flags = 0;
> +	const char *test_name = "sys membarrier MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE";
> +
> +	if (sys_membarrier(cmd, flags) != 0) {
> +		ksft_exit_fail_msg(
> +			"%s test: flags = %d, errno = %d\n",
> +			test_name, flags, errno);
> +	}
> +
> +	ksft_test_result_pass(
> +		"%s test: flags = %d\n",
> +		test_name, flags);
> +	return 0;
> +}
> +
>  static int test_membarrier_register_shared_expedited_success(void)
>  {
>  	int cmd = MEMBARRIER_CMD_REGISTER_SHARED_EXPEDITED, flags = 0;
> @@ -188,6 +245,22 @@ static int test_membarrier(void)
>  	status = test_membarrier_private_expedited_success();
>  	if (status)
>  		return status;
> +	status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0);
> +	if (status < 0) {
> +		ksft_test_result_fail("sys_membarrier() failed\n");
> +		return status;
> +	}
> +	if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
> +		status = test_membarrier_private_expedited_sync_core_fail();
> +		if (status)
> +			return status;
> +		status = test_membarrier_register_private_expedited_sync_core_success();
> +		if (status)
> +			return status;
> +		status = test_membarrier_private_expedited_sync_core_success();
> +		if (status)
> +			return status;
> +	}
>  	/*
>  	 * It is valid to send a shared membarrier from a non-registered
>  	 * process.
> 

Looks good to me. I am assuming this patch goes in with the rest of the
series. For this patch:

Acked-by: Shuah Khan <shuahkh@osg.samsung.com>

thanks,
-- Shuah

Re: [RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Mathieu Desnoyers]

----- On Nov 17, 2017, at 10:09 AM, Shuah Khan shuahkh@osg.samsung.com wrote:
> 
> Looks good to me. I am assuming this patch goes in with the rest of the
> series. For this patch:
> 
> Acked-by: Shuah Khan <shuahkh@osg.samsung.com>

Thanks for the Acked-by. I'll add it to the patch changelog.
The sync_core membarrier patches are now queued for 4.16 however.

Thanks,

Mathieu

> 
> thanks,
> -- Shuah

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

Re: [RFC PATCH for 4.15 23/24] membarrier: selftest: Test private expedited sync core cmd

[Mathieu Desnoyers]

----- On Nov 17, 2017, at 10:09 AM, Shuah Khan shuahkh@osg.samsung.com wrote:
> 
> Looks good to me. I am assuming this patch goes in with the rest of the
> series. For this patch:
> 
> Acked-by: Shuah Khan <shuahkh@osg.samsung.com>

Thanks for the Acked-by. I'll add it to the patch changelog.
The sync_core membarrier patches are now queued for 4.16 however.

Thanks,

Mathieu

> 
> thanks,
> -- Shuah

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

[RFC PATCH for 4.15 24/24] membarrier: arm64: Provide core serializing command

[Mathieu Desnoyers]

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: x86@kernel.org
CC: linux-arch@vger.kernel.org
---
 arch/arm64/Kconfig        | 1 +
 arch/arm64/kernel/entry.S | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0df64a6a56d4..38272601850d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -16,6 +16,7 @@ config ARM64
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e1c59d4008a8..0ec02508e53c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -300,6 +300,10 @@ alternative_else_nop_endif
 	ldp	x28, x29, [sp, #16 * 14]
 	ldr	lr, [sp, #S_LR]
 	add	sp, sp, #S_FRAME_SIZE		// restore sp
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
+	 * when returning from IPI handler, and when returning to user-space.
+	 */
 	eret					// return to kernel
 	.endm
 
-- 
2.11.0

[RFC PATCH for 4.15 24/24] membarrier: arm64: Provide core serializing command

[Mathieu Desnoyers]

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: x86@kernel.org
CC: linux-arch@vger.kernel.org
---
 arch/arm64/Kconfig        | 1 +
 arch/arm64/kernel/entry.S | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0df64a6a56d4..38272601850d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -16,6 +16,7 @@ config ARM64
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e1c59d4008a8..0ec02508e53c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -300,6 +300,10 @@ alternative_else_nop_endif
 	ldp	x28, x29, [sp, #16 * 14]
 	ldr	lr, [sp, #S_LR]
 	add	sp, sp, #S_FRAME_SIZE		// restore sp
+	/*
+	 * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
+	 * when returning from IPI handler, and when returning to user-space.
+	 */
 	eret					// return to kernel
 	.endm
 
-- 
2.11.0