Re: [Qemu-devel] [kvm-unit-tests PATCH v11 1/3] arm: Add PMU test

[Andrew Jones]

On Wed, Nov 23, 2016 at 01:16:08PM +0000, Andre Przywara wrote:
> Hi,
> 
> On 22/11/16 18:29, Wei Huang wrote:
> > From: Christopher Covington <address@hidden>
> > 
> > Beginning with a simple sanity check of the control register, add
> > a unit test for the ARM Performance Monitors Unit (PMU).
> 
> Mmh, the output of this is a bit confusing. How about to join some
> information? I changed it to give me:
> INFO: pmu: PMU implementer/ID code:     "A"(0x41)/0x0
> INFO: pmu: Event counters:      0
> PASS: pmu: Control register
> 
> ... by using the newly introduced report_info() to make it look nicer.

Agreed. That would look nicer and make good use of report_info. Let's
do that.

> 
> > 
> > Signed-off-by: Christopher Covington <address@hidden>
> > Signed-off-by: Wei Huang <address@hidden>
> > Reviewed-by: Andrew Jones <address@hidden>
> > ---
> >  arm/Makefile.common |  3 ++-
> >  arm/pmu.c           | 74 
> > +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  arm/unittests.cfg   |  5 ++++
> >  3 files changed, 81 insertions(+), 1 deletion(-)
> >  create mode 100644 arm/pmu.c
> > 
> > diff --git a/arm/Makefile.common b/arm/Makefile.common
> > index f37b5c2..5da2fdd 100644
> > --- a/arm/Makefile.common
> > +++ b/arm/Makefile.common
> > @@ -12,7 +12,8 @@ endif
> >  tests-common = \
> >     $(TEST_DIR)/selftest.flat \
> >     $(TEST_DIR)/spinlock-test.flat \
> > -   $(TEST_DIR)/pci-test.flat
> > +   $(TEST_DIR)/pci-test.flat \
> > +   $(TEST_DIR)/pmu.flat
> >  
> >  all: test_cases
> >  
> > diff --git a/arm/pmu.c b/arm/pmu.c
> > new file mode 100644
> > index 0000000..9d9c53b
> > --- /dev/null
> > +++ b/arm/pmu.c
> > @@ -0,0 +1,74 @@
> > +/*
> > + * Test the ARM Performance Monitors Unit (PMU).
> > + *
> > + * Copyright (c) 2015-2016, The Linux Foundation. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU Lesser General Public License version 2.1 and
> > + * only version 2.1 as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful, but 
> > WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
> > License
> > + * for more details.
> > + */
> > +#include "libcflat.h"
> > +#include "asm/barrier.h"
> > +
> > +#define PMU_PMCR_N_SHIFT   11
> > +#define PMU_PMCR_N_MASK    0x1f
> > +#define PMU_PMCR_ID_SHIFT  16
> > +#define PMU_PMCR_ID_MASK   0xff
> > +#define PMU_PMCR_IMP_SHIFT 24
> > +#define PMU_PMCR_IMP_MASK  0xff
> > +
> > +#if defined(__arm__)
> 
> I guess you should use the arch specific header files we have in place
> for that (lib/arm{.64}/asm/processor.h). Also there are sysreg read
> wrappers (at least for arm64) in there already, can't we base this
> function on them: DEFINE_GET_SYSREG32(pmcr, el0)?
> (Requires a small change to get rid of the forced "_el1" suffix)
> 
> We should wait for the GIC series to be merged, as this contains some
> changes in this area.

As this unit test is the only consumer of PMC registers so far, then
I'd prefer the defines and accessors stay here for now. Once we see
a use in other unit tests then we can move some of it out.

> 
> > +static inline uint32_t pmcr_read(void)
> > +{
> > +   uint32_t ret;
> > +
> > +   asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret));
> > +   return ret;
> > +}
> > +#elif defined(__aarch64__)
> > +static inline uint32_t pmcr_read(void)
> > +{
> > +   uint32_t ret;
> > +
> > +   asm volatile("mrs %0, pmcr_el0" : "=r" (ret));
> > +   return ret;
> > +}
> > +#endif
> > +
> > +/*
> > + * As a simple sanity check on the PMCR_EL0, ensure the implementer field 
> > isn't
> > + * null. Also print out a couple other interesting fields for diagnostic
> > + * purposes. For example, as of fall 2016, QEMU TCG mode doesn't implement
> > + * event counters and therefore reports zero event counters, but hopefully
> > + * support for at least the instructions event will be added in the future 
> > and
> > + * the reported number of event counters will become nonzero.
> > + */
> > +static bool check_pmcr(void)
> > +{
> > +   uint32_t pmcr;
> > +
> > +   pmcr = pmcr_read();
> > +
> > +   printf("PMU implementer:     %c\n",
> > +          (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK);
> 
> If this register reads as zero, the output is mangled (since it cuts off
> the string before the newline):
> =====
> PMU implementer:     Identification code: 0x0
> =====
> 
> I guess you need something like:
> (pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK ?: ' '

Good idea.

> 
> > +   printf("Identification code: 0x%x\n",
> > +          (pmcr >> PMU_PMCR_ID_SHIFT) & PMU_PMCR_ID_MASK);
> 
> As mentioned above this should use report_info() now, also it would be
> nice to merge this with the message above into one line of output.

Agreed.

Thanks,
drew

> 
> Cheers,
> Andre
> 
> > +   printf("Event counters:      %d\n",
> > +          (pmcr >> PMU_PMCR_N_SHIFT) & PMU_PMCR_N_MASK);
> > +
> > +   return ((pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK) != 0;
> > +}
> > +
> > +int main(void)
> > +{
> > +   report_prefix_push("pmu");
> > +
> > +   report("Control register", check_pmcr());
> > +
> > +   return report_summary();
> > +}
> > diff --git a/arm/unittests.cfg b/arm/unittests.cfg
> > index ae32a42..816f494 100644
> > --- a/arm/unittests.cfg
> > +++ b/arm/unittests.cfg
> > @@ -58,3 +58,8 @@ groups = selftest
> >  [pci-test]
> >  file = pci-test.flat
> >  groups = pci
> > +
> > +# Test PMU support
> > +[pmu]
> > +file = pmu.flat
> > +groups = pmu
> > 
>