Re: [kvm-unit-tests PATCH v6 1/2] s390x: topology: Check the Perform Topology Function

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On 2/10/23 15:51, Nina Schoetterl-Glausch wrote:
On Thu, 2023-02-02 at 10:28 +0100, Pierre Morel wrote:
We check that the PTF instruction is working correctly when
the cpu topology facility is available.

For KVM only, we test changing of the polarity between horizontal
and vertical and that a reset set the horizontal polarity.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
  s390x/Makefile      |   1 +
  s390x/topology.c    | 155 ++++++++++++++++++++++++++++++++++++++++++++
  s390x/unittests.cfg |   3 +
  3 files changed, 159 insertions(+)
  create mode 100644 s390x/topology.c

diff --git a/s390x/Makefile b/s390x/Makefile
index 52a9d82..b5fe8a3 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -39,6 +39,7 @@ tests += $(TEST_DIR)/panic-loop-extint.elf
  tests += $(TEST_DIR)/panic-loop-pgm.elf
  tests += $(TEST_DIR)/migration-sck.elf
  tests += $(TEST_DIR)/exittime.elf
+tests += $(TEST_DIR)/topology.elf
pv-tests += $(TEST_DIR)/pv-diags.elf diff --git a/s390x/topology.c b/s390x/topology.c
new file mode 100644
index 0000000..20f7ba2
--- /dev/null
+++ b/s390x/topology.c
@@ -0,0 +1,155 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * CPU Topology
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * Authors:
+ *  Pierre Morel <pmorel@xxxxxxxxxxxxx>
+ */
+
+#include <libcflat.h>
+#include <asm/page.h>
+#include <asm/asm-offsets.h>
+#include <asm/interrupt.h>
+#include <asm/facility.h>
+#include <smp.h>
+#include <sclp.h>
+#include <s390x/hardware.h>
+
+#define PTF_REQ_HORIZONTAL	0
+#define PTF_REQ_VERTICAL	1
+#define PTF_REQ_CHECK		2
+
+#define PTF_ERR_NO_REASON	0
+#define PTF_ERR_ALRDY_POLARIZED	1
+#define PTF_ERR_IN_PROGRESS	2

Maybe also give the CC codes names for improved readability.

OK


+
+extern int diag308_load_reset(u64);
+
+static int ptf(unsigned long fc, unsigned long *rc)
+{
+	int cc;
+
+	asm volatile(
+		"       .insn   rre,0xb9a20000,%1,0\n"
+		"       ipm     %0\n"
+		"       srl     %0,28\n"
+		: "=d" (cc), "+d" (fc)
+		:
+		: "cc");

Personally I always name asm arguments, but it is a very short snippet,
so still very readable. Could also pull the shift into C code,
but again, small difference.

+
+	*rc = fc >> 8;
+	return cc;
+}
+
+static void test_ptf(void)
+{
+	unsigned long rc;
+	int cc;
+
+	/* PTF is a privilege instruction */
+	report_prefix_push("Privilege");
+	enter_pstate();
+	expect_pgm_int();
+	ptf(PTF_REQ_CHECK, &rc);
+	check_pgm_int_code(PGM_INT_CODE_PRIVILEGED_OPERATION);
+	report_prefix_pop();

IMO, you should repeat this test for all FCs, since some are emulated,
others interpreted by SIE.

right


+
+	report_prefix_push("Wrong fc");

"Undefined fc" is more informative IMO.

OK


+	expect_pgm_int();
+	ptf(0xff, &rc);
+	check_pgm_int_code(PGM_INT_CODE_SPECIFICATION);
+	report_prefix_pop();
+
+	report_prefix_push("Reserved bits");
+	expect_pgm_int();
+	ptf(0xffffffffffffff00UL, &rc);
+	check_pgm_int_code(PGM_INT_CODE_SPECIFICATION);
+	report_prefix_pop();
+
+	report_prefix_push("Topology Report pending");
+	/*
+	 * At this moment the topology may already have changed
+	 * since the VM has been started.
+	 * However, we can test if a second PTF instruction
+	 * reports that the topology did not change since the
+	 * preceding PFT instruction.
+	 */
+	ptf(PTF_REQ_CHECK, &rc);
+	cc = ptf(PTF_REQ_CHECK, &rc);
+	report(cc == 0, "PTF check should clear topology report");
+	report_prefix_pop();
+
+	report_prefix_push("Topology polarisation check");
+	/*
+	 * We can not assume the state of the polarization for
+	 * any Virtual Machine but KVM.

Random Capitalization :)

OK

Why can you not test the same thing for other hypervisors/LPAR?

At first QEMU did not support vertical polarization so my tests would have get a false negative on LPAR.
I could have done different tests but did not.

I think that now it is alright to do the checks on LPAR too.



+	 * Let's skip the polarisation tests for other VMs.
+	 */
+	if (!host_is_kvm()) {
+		report_skip("Topology polarisation check is done for KVM only");
+		goto end;
+	}
+
+	/*
+	 * Set vertical polarization to verify that RESET sets
+	 * horizontal polarization back.
+	 */

You might want to do a reset here also, since there could be some other
test case that could have run before and modified the polarization.
There isn't right now of course, but doing a reset improves separation of tests.

Not sure about this but it does not arm so why not.

Thanks.

regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen



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