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

[Pierre Morel <pmorel@linux.ibm.com>]

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@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.

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