[V2 0/2] selftests/powerpc: Updates to EBB selftest for ISA v3.1

[V2 0/2] selftests/powerpc: Updates to EBB selftest for ISA v3.1

[Athira Rajeev]

The "no_handler_test" in ebb selftests attempts to read the PMU
registers after closing of the event via helper function
"dump_ebb_state". With the MMCR0 control bit (PMCCEXT) in ISA v3.1,
read access to group B registers is restricted when MMCR0 PMCC=0b00.
Hence the call to dump_ebb_state after closing of event will generate
a SIGILL, which is expected.

Test has below in logs:
<<>>
!! child died by signal 4
failure: no_handler_test
<<>>

In other platforms (like power9), the older behaviour works where
group B PMU SPRs are readable. The "dump_ebb_state" is called twice
in the test. The second call after closing of event was done inorder
to dump state of registers when the counters are frozen. But since
the counters should already be frozen by the time first dump is done,
patch1 drops the second call to "dump_ebb_state".

To address the new sigill behaviour in ISA v3.1, patch2 creates
a separate selftest.

Changelog:
v1 -> v2:
        Addressed review comments from Michael Ellerman.
        First version attempted to address the SIGILL
        behaviour in existing "no_handler_test" test itself.
        As per mpe's suggestion, moved that to a separate test
        and removed the second call to "dump_ebb_state" since
        that is actually not needed.

Athira Rajeev (2):
  selftests/powerpc: Fix "no_handler" EBB selftest
  selftests/powerpc: EBB selftest for MMCR0 control for PMU SPRs in ISA
    v3.1

 tools/testing/selftests/powerpc/pmu/ebb/Makefile   |  2 +-
 .../selftests/powerpc/pmu/ebb/no_handler_test.c    |  2 -
 .../powerpc/pmu/ebb/regs_access_pmccext_test.c     | 63 ++++++++++++++++++++++
 3 files changed, 64 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c

-- 
1.8.3.1

[V2 1/2] selftests/powerpc: Fix "no_handler" EBB selftest

[Athira Rajeev]

The "no_handler_test" in ebb selftests attempts to read the PMU
registers twice via helper function "dump_ebb_state". First dump is
just before closing of event and the second invocation is done after
closing of the event. The original intention of second
dump_ebb_state was to dump the state of registers at the end of
the test when the counters are frozen. But this will be achieved
with the first call itself since sample period is set to low value
and PMU will be frozen by then. Hence patch removes the
dump which was done before closing of the event.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reported-by: Shirisha Ganta <shirisha.ganta1@ibm.com>
---
 tools/testing/selftests/powerpc/pmu/ebb/no_handler_test.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/tools/testing/selftests/powerpc/pmu/ebb/no_handler_test.c b/tools/testing/selftests/powerpc/pmu/ebb/no_handler_test.c
index fc5bf48..01e827c 100644
--- a/tools/testing/selftests/powerpc/pmu/ebb/no_handler_test.c
+++ b/tools/testing/selftests/powerpc/pmu/ebb/no_handler_test.c
@@ -50,8 +50,6 @@ static int no_handler_test(void)
 
 	event_close(&event);
 
-	dump_ebb_state();
-
 	/* The real test is that we never took an EBB at 0x0 */
 
 	return 0;
-- 
1.8.3.1

[V2 2/2] selftests/powerpc: EBB selftest for MMCR0 control for PMU SPRs in ISA v3.1

[Athira Rajeev]

With the MMCR0 control bit (PMCCEXT) in ISA v3.1, read access to
group B registers is restricted when MMCR0 PMCC=0b00. In other
platforms (like power9), the older behaviour works where group B
PMU SPRs are readable.

Patch creates a selftest which verifies that the test takes a
SIGILL when attempting to read PMU registers via helper function
"dump_ebb_state" for ISA v3.1.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
---
 tools/testing/selftests/powerpc/pmu/ebb/Makefile   |  2 +-
 .../powerpc/pmu/ebb/regs_access_pmccext_test.c     | 63 ++++++++++++++++++++++
 2 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c

diff --git a/tools/testing/selftests/powerpc/pmu/ebb/Makefile b/tools/testing/selftests/powerpc/pmu/ebb/Makefile
index c5ecb46..0101606 100644
--- a/tools/testing/selftests/powerpc/pmu/ebb/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/ebb/Makefile
@@ -24,7 +24,7 @@ TEST_GEN_PROGS := reg_access_test event_attributes_test cycles_test	\
 	 fork_cleanup_test ebb_on_child_test			\
 	 ebb_on_willing_child_test back_to_back_ebbs_test	\
 	 lost_exception_test no_handler_test			\
-	 cycles_with_mmcr2_test
+	 cycles_with_mmcr2_test regs_access_pmccext_test
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk
diff --git a/tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c b/tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c
new file mode 100644
index 0000000..5f1a040
--- /dev/null
+++ b/tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2021, Athira Rajeev, IBM Corp.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <setjmp.h>
+#include <signal.h>
+
+#include "ebb.h"
+
+
+/*
+ * Test that closing the EBB event clears MMCR0_PMCC and
+ * sets MMCR0_PMCCEXT preventing further read access to the
+ * group B PMU registers.
+ */
+
+static int regs_access_pmccext(void)
+{
+	struct event event;
+
+	SKIP_IF(!ebb_is_supported());
+
+	event_init_named(&event, 0x1001e, "cycles");
+	event_leader_ebb_init(&event);
+
+	FAIL_IF(event_open(&event));
+
+	ebb_enable_pmc_counting(1);
+	setup_ebb_handler(standard_ebb_callee);
+	ebb_global_enable();
+	FAIL_IF(ebb_event_enable(&event));
+
+	mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
+
+	while (ebb_state.stats.ebb_count < 1)
+		FAIL_IF(core_busy_loop());
+
+	ebb_global_disable();
+	event_close(&event);
+
+	FAIL_IF(ebb_state.stats.ebb_count == 0);
+
+	/*
+	 * For ISA v3.1, verify the test takes a SIGILL when reading
+	 * PMU regs after the event is closed. With the control bit
+	 * in MMCR0 (PMCCEXT) restricting access to group B PMU regs,
+	 * sigill is expected.
+	 */
+	if (have_hwcap2(PPC_FEATURE2_ARCH_3_1))
+		FAIL_IF(catch_sigill(dump_ebb_state));
+	else
+		dump_ebb_state();
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(regs_access_pmccext,"regs_access_pmccext");
+}
-- 
1.8.3.1