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

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

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@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
> > +
> > +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