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

[Nina Schoetterl-Glausch <nsg@linux.ibm.com>]

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@linux.ibm.com>
> ---
>  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@linux.ibm.com>
> + */
> +
> +#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.

> +
> +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.

> +
> +	report_prefix_push("Wrong fc");

"Undefined fc" is more informative IMO.

> +	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 :)
Why can you not test the same thing for other hypervisors/LPAR?

> +	 * 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.

> +	cc = ptf(PTF_REQ_VERTICAL, &rc);
> +	report(cc == 0, "Set vertical polarization.");
> +
> +	report(diag308_load_reset(1), "load normal reset done");
> +
> +	cc = ptf(PTF_REQ_CHECK, &rc);
> +	report(cc == 0, "Reset should clear topology report");
> +
> +	cc = ptf(PTF_REQ_HORIZONTAL, &rc);
> +	report(cc == 2 && rc == PTF_ERR_ALRDY_POLARIZED,
> +	       "After RESET polarization is horizontal");
> +
> +	/* Flip between vertical and horizontal polarization */
> +	cc = ptf(PTF_REQ_VERTICAL, &rc);
> +	report(cc == 0, "Change to vertical polarization.");
> +
> +	cc = ptf(PTF_REQ_CHECK, &rc);
> +	report(cc == 1, "Polarization change should set topology report");
> +
> +	cc = ptf(PTF_REQ_HORIZONTAL, &rc);
> +	report(cc == 0, "Change to horizontal polarization.");
> +
> +end:
> +	report_prefix_pop();
> +}
> +
> +static struct {
> +	const char *name;
> +	void (*func)(void);
> +} tests[] = {
> +	{ "PTF", test_ptf},
> +	{ NULL, NULL }
> +};
> +
> +int main(int argc, char *argv[])
> +{
> +	int i;
> +
> +	report_prefix_push("CPU Topology");
> +
> +	if (!test_facility(11)) {
> +		report_skip("Topology facility not present");
> +		goto end;
> +	}
> +
> +	report_info("Virtual machine level %ld", stsi_get_fc());
> +
> +	for (i = 0; tests[i].name; i++) {
> +		report_prefix_push(tests[i].name);
> +		tests[i].func();
> +		report_prefix_pop();
> +	}
> +
> +end:
> +	report_prefix_pop();
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 3caf81e..3530cc4 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -208,3 +208,6 @@ groups = migration
>  [exittime]
>  file = exittime.elf
>  smp = 2
> +
> +[topology]
> +file = topology.elf