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    Subject[PATCH 1/8] perf/x86: Add msr probe interface
    Date
    Adding perf_msr_probe function to provide interface for
    checking up on MSR register and set the related attribute
    group visibility.

    User defines following struct for each MSR register:

    struct perf_msr {
    u64 msr;
    struct attribute_group *grp;
    bool (*test)(int idx, void *data);
    bool no_check;
    };

    Where:
    msr - is the MSR address
    attrs - is attribute groups array to add if the check passed
    test - is test function pointer
    no_check - is bool that bypass the check and adds the
    attribute without any test

    The array of struct perf_msr is passed into:

    perf_msr_probe(struct perf_msr *msr, int cnt, void *data)

    Together with:
    cnt - which is the number of struct msr array elements
    data -which is user pointer passed to the test function

    The perf_msr_probe will executed test code, read the MSR and
    check the value is != 0. If all these tests pass, related
    attribute group is kept visible.

    Also adding PMU_EVENT_GROUP macro helper to define attribute
    group for single attribute. It will be used in following patches.

    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    ---
    arch/x86/events/Makefile | 2 +-
    arch/x86/events/probe.c | 42 ++++++++++++++++++++++++++++++++++++++++
    arch/x86/events/probe.h | 29 +++++++++++++++++++++++++++
    3 files changed, 72 insertions(+), 1 deletion(-)
    create mode 100644 arch/x86/events/probe.c
    create mode 100644 arch/x86/events/probe.h

    diff --git a/arch/x86/events/Makefile b/arch/x86/events/Makefile
    index b8ccdb5c9244..ec29a466444a 100644
    --- a/arch/x86/events/Makefile
    +++ b/arch/x86/events/Makefile
    @@ -1,4 +1,4 @@
    -obj-y += core.o
    +obj-y += core.o probe.o
    obj-y += amd/
    obj-$(CONFIG_X86_LOCAL_APIC) += msr.o
    obj-$(CONFIG_CPU_SUP_INTEL) += intel/
    diff --git a/arch/x86/events/probe.c b/arch/x86/events/probe.c
    new file mode 100644
    index 000000000000..0b190f779ee1
    --- /dev/null
    +++ b/arch/x86/events/probe.c
    @@ -0,0 +1,42 @@
    +// SPDX-License-Identifier: GPL-2.0
    +#include <linux/export.h>
    +#include <linux/types.h>
    +#include <linux/bits.h>
    +#include "probe.h"
    +
    +static umode_t
    +not_visible(struct kobject *kobj, struct attribute *attr, int i)
    +{
    + return 0;
    +}
    +
    +unsigned long
    +perf_msr_probe(struct perf_msr *msr, int cnt, void *data)
    +{
    + unsigned long avail = 0;
    + unsigned int bit;
    + u64 val;
    +
    + if (cnt >= BITS_PER_LONG)
    + return 0;
    +
    + for (bit = 0; bit < cnt; bit++) {
    + if (!msr[bit].no_check) {
    + struct attribute_group *grp = msr[bit].grp;
    +
    + grp->is_visible = not_visible;
    +
    + if (msr[bit].test && !msr[bit].test(bit, data))
    + continue;
    + /* Virt sucks; you cannot tell if a R/O MSR is present :/ */
    + if (rdmsrl_safe(msr[bit].msr, &val) || !val)
    + continue;
    +
    + grp->is_visible = NULL;
    + }
    + avail |= BIT(bit);
    + }
    +
    + return avail;
    +}
    +EXPORT_SYMBOL_GPL(perf_msr_probe);
    diff --git a/arch/x86/events/probe.h b/arch/x86/events/probe.h
    new file mode 100644
    index 000000000000..f2c34c25f8a5
    --- /dev/null
    +++ b/arch/x86/events/probe.h
    @@ -0,0 +1,29 @@
    +/* SPDX-License-Identifier: GPL-2.0 */
    +#ifndef __ARCH_X86_EVENTS_PROBE_H__
    +#define __ARCH_X86_EVENTS_PROBE_H__
    +#include <linux/sysfs.h>
    +
    +struct perf_msr {
    + u64 msr;
    + struct attribute_group *grp;
    + bool (*test)(int idx, void *data);
    + bool no_check;
    +};
    +
    +unsigned long
    +perf_msr_probe(struct perf_msr *msr, int cnt, void *data);
    +
    +#define __PMU_EVENT_GROUP(_name) \
    +static struct attribute *attrs_##_name[] = { \
    + &attr_##_name.attr.attr, \
    + NULL, \
    +}
    +
    +#define PMU_EVENT_GROUP(_grp, _name) \
    +__PMU_EVENT_GROUP(_name); \
    +static struct attribute_group group_##_name = { \
    + .name = #_grp, \
    + .attrs = attrs_##_name, \
    +}
    +
    +#endif /* __ARCH_X86_EVENTS_PROBE_H__ */
    --
    2.20.1
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