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

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

On 2/8/23 12:06, Thomas Huth wrote:
> On 02/02/2023 10.28, 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
>> +
>> +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"
> 
> Why are you specifying the instruction manually? I think both, GCC and 
> Clang should know the "ptf" mnemonic, shouldn't they?

:D right !

> 
>> +        "       ipm     %0\n"
>> +        "       srl     %0,28\n"
>> +        : "=d" (cc), "+d" (fc)
>> +        :
>> +        : "cc");
>> +
>> +    *rc = fc >> 8;
>> +    return cc;
>> +}
>> +
>> +static void test_ptf(void)
>> +{
>> +    unsigned long rc;
>> +    int cc;
>> +
>> +    /* PTF is a privilege instruction */
> 
> s/privilege/privileged/ ?

Yes, thanks

> 
>> +    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();
>> +
>> +    report_prefix_push("Wrong fc");
>> +    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();
> 
> This function is quite big ... I'd maybe group the above checks for 
> error conditions into a separate function instead.

OK

> 
>> +    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
> 
> s/can not/cannot/ ?

OK

> 
> Also, you sometimes write polarization with "z" and sometimes with "s". 
> I'd suggest to standardize on "z" (as in "IBM Z" ;-))

OK

> 
>> +     * any Virtual Machine but KVM.
>> +     * 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.
>> +     */
>> +    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();
>> +}
> 
> Apart from the nits, the patch looks fine to me.
> 
>   Thomas
> 

Thanks,

Regards.
Pierre





-- 
Pierre Morel
IBM Lab Boeblingen