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

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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>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com <mailto:rnsastry@linux.ibm.com>>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1621950703-1532-3-git-send-email-atrajeev@linux.vnet.ibm.com
This commit is contained in:
Athira Rajeev 2021-05-25 09:51:43 -04:00 committed by Michael Ellerman
parent 45677c9aeb
commit d81090ed44
2 changed files with 64 additions and 1 deletions
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2
tools/testing/selftests/powerpc/pmu/ebb/Makefile
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@ -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

63
tools/testing/selftests/powerpc/pmu/ebb/regs_access_pmccext_test.c Normal file
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@ -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");
}