Re: [PATCH v8 8/9] perf/amd/iommu: Fix sysfs perf attribute groups

Borislav Petkov
2017-01-22T19:54:50Z

On Mon, Jan 16, 2017 at 01:23:35AM -0600, Suravee Suthikulpanit wrote:
> From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
>
> Introduce static amd_iommu_attr_groups to simplify the
> sysfs attributes initialization code.
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
> ---
> arch/x86/events/amd/iommu.c | 85 ++++++++++++++++++++-------------------------
> 1 file changed, 37 insertions(+), 48 deletions(-)
>
> diff --git a/arch/x86/events/amd/iommu.c b/arch/x86/events/amd/iommu.c
> index cc7bea4..223c01d 100644
> --- a/arch/x86/events/amd/iommu.c
> +++ b/arch/x86/events/amd/iommu.c
> @@ -43,14 +43,8 @@ struct perf_amd_iommu {
> u8 max_counters;
> u64 cntr_assign_mask;
> raw_spinlock_t lock;
> - const struct attribute_group *attr_groups[4];
> };
>
> -#define format_group attr_groups[0]
> -#define cpumask_group attr_groups[1]
> -#define events_group attr_groups[2]
> -#define null_group attr_groups[3]
> -
> /*---------------------------------------------
> * sysfs format attributes
> *---------------------------------------------*/
> @@ -81,6 +75,10 @@ struct perf_amd_iommu {
> /*---------------------------------------------
> * sysfs events attributes
> *---------------------------------------------*/
> +static struct attribute_group amd_iommu_events_group = {
> + .name = "events",
> +};
> +
> struct amd_iommu_event_desc {
> struct kobj_attribute attr;
> const char *event;
> @@ -388,76 +386,63 @@ static void perf_iommu_del(struct perf_event *event, int flags)
> perf_event_update_userpage(event);
> }
>
> -static __init int _init_events_attrs(struct perf_amd_iommu *perf_iommu)
> +static __init int _init_events_attrs(void)
> {
> - struct attribute **attrs;
> - struct attribute_group *attr_group;
> int i = 0, j;
> + struct attribute **attrs;
>
> while (amd_iommu_v2_event_descs[i].attr.attr.name)
> i++;
>
> - attr_group = kzalloc(sizeof(struct attribute *)
> - * (i + 1) + sizeof(*attr_group), GFP_KERNEL);
> - if (!attr_group)
> + attrs = kzalloc(sizeof(struct attribute **) * (i + 1), GFP_KERNEL);
> + if (!attrs)
> return -ENOMEM;
>
> - attrs = (struct attribute **)(attr_group + 1);
> for (j = 0; j < i; j++)
> attrs[j] = &amd_iommu_v2_event_descs[j].attr.attr;
>
> - attr_group->name = "events";
> - attr_group->attrs = attrs;
> - perf_iommu->events_group = attr_group;
> -
> + amd_iommu_events_group.attrs = attrs;
> return 0;
> }
>
> static __init void amd_iommu_pc_exit(void)
> {
> - if (__perf_iommu.events_group != NULL) {
> - kfree(__perf_iommu.events_group);
> - __perf_iommu.events_group = NULL;
> + if (amd_iommu_events_group.attrs) {
> + kfree(amd_iommu_events_group.attrs);

Please integrate scripts/checkpatch.pl in your patch creation workflow.
Some of the warnings/errors *actually* make sense. Like this one:

WARNING: kfree(NULL) is safe and this check is probably not required
#98: FILE: arch/x86/events/amd/iommu.c:411:
+ if (amd_iommu_events_group.attrs) {
+ kfree(amd_iommu_events_group.attrs);

> + amd_iommu_events_group.attrs = NULL;

You keep doing that. Why?

> }
> }
>
> -static __init int _init_perf_amd_iommu(
> - struct perf_amd_iommu *perf_iommu, char *name)
> +const struct attribute_group *amd_iommu_attr_groups[] = {
> + &amd_iommu_format_group,
> + &amd_iommu_cpumask_group,
> + &amd_iommu_events_group,
> + NULL,
> +};
> +
> +static __init int
> +_init_perf_amd_iommu(struct perf_amd_iommu *perf_iommu, char *name)
> {
> int ret;
>
> raw_spin_lock_init(&perf_iommu->lock);
>
> - perf_iommu->format_group = &amd_iommu_format_group;
> -
> /* Init cpumask attributes to only core 0 */
> cpumask_set_cpu(0, &iommu_cpumask);
> - perf_iommu->cpumask_group = &amd_iommu_cpumask_group;
> -
> - ret = _init_events_attrs(perf_iommu);
> - if (ret) {
> - pr_err("Error initializing AMD IOMMU perf events.\n");
> - return ret;
> - }
>
> perf_iommu->max_banks = amd_iommu_pc_get_max_banks(0);
> perf_iommu->max_counters = amd_iommu_pc_get_max_counters(0);
> if (!perf_iommu->max_banks || !perf_iommu->max_counters)
> return -EINVAL;
>
> - perf_iommu->null_group = NULL;
> - perf_iommu->pmu.attr_groups = perf_iommu->attr_groups;
> -
> + perf_iommu->pmu.attr_groups = amd_iommu_attr_groups;
> ret = perf_pmu_register(&perf_iommu->pmu, name, -1);
> - if (ret) {
> + if (ret)
> pr_err("Error initializing AMD IOMMU perf counters.\n");
> - amd_iommu_pc_exit();
> - } else {
> + else
> pr_info("perf: amd_iommu: Detected. (%d banks, %d counters/bank)\n",
> amd_iommu_pc_get_max_banks(0),
> amd_iommu_pc_get_max_counters(0));
> - }
> -
> return ret;
> }
>
> @@ -471,24 +456,28 @@ static __init int _init_perf_amd_iommu(
> .stop = perf_iommu_stop,
> .read = perf_iommu_read,
> },
> - .max_banks = 0x00,
> - .max_counters = 0x00,
> - .cntr_assign_mask = 0ULL,
> - .format_group = NULL,
> - .cpumask_group = NULL,
> - .events_group = NULL,
> - .null_group = NULL,
> };
>
> static __init int amd_iommu_pc_init(void)
> {
> + int ret;
> +
> /* Make sure the IOMMU PC resource is available */
> if (!amd_iommu_pc_supported())
> return -ENODEV;
>
> - _init_perf_amd_iommu(&__perf_iommu, "amd_iommu");
> + ret = _init_events_attrs();
> + if (ret)
> + goto err_out;

So that's actually

if (ret)
return ret;

to propagate the -ENOMEM.

>
> - return 0;
> + ret = _init_perf_amd_iommu(&__perf_iommu, "amd_iommu");
> + if (ret)
> + goto err_out;

Then here you can do:

if (ret)
amd_iommu_pc_exit();

return ret;

and simplify it a bit and get rid of the err_out label.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.