Re: [PATCH v4 10/13] x86/resctrl: Add the sysfs interface to read the event configuration

Reinette Chatre
2022-09-16T15:59:51Z

Hi Babu,

On 9/7/2022 11:01 AM, Babu Moger wrote:
> The current event configuration can be viewed by the user by reading
> the sysfs configuration file.
>
> Following are the types of events supported:
>
> ==== ===========================================================
> Bits Description
> ==== ===========================================================
> 6 Dirty Victims from the QOS domain to all types of memory
> 5 Reads to slow memory in the non-local NUMA domain
> 4 Reads to slow memory in the local NUMA domain
> 3 Non-temporal writes to non-local NUMA domain
> 2 Non-temporal writes to local NUMA domain
> 1 Reads to memory in the non-local NUMA domain
> 0 Reads to memory in the local NUMA domain
> ==== ===========================================================
>

...

> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 45923eb4022f..96f439324d78 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -15,6 +15,7 @@
> #define MSR_IA32_MBA_THRTL_BASE 0xd50
> #define MSR_IA32_MBA_BW_BASE 0xc0000200
> #define MSR_IA32_SMBA_BW_BASE 0xc0000280
> +#define MSR_IA32_EVT_CFG_BASE 0xc0000400
>
> #define MSR_IA32_QM_CTR 0x0c8e
> #define MSR_IA32_QM_EVTSEL 0x0c8d
> @@ -50,6 +51,29 @@
> */
> #define MBM_CNTR_WIDTH_OFFSET_MAX (62 - MBM_CNTR_WIDTH_BASE)
>
> +/* Reads to Local DRAM Memory */

What prompted the terminology switch between the
changelog ("local NUMA") and the comments ("DRAM")?

> +#define READS_TO_LOCAL_MEM BIT(0)
> +
> +/* Reads to Remote DRAM Memory */
> +#define READS_TO_REMOTE_MEM BIT(1)
> +
> +/* Non-Temporal Writes to Local Memory */
> +#define NON_TEMP_WRITE_TO_LOCAL_MEM BIT(2)
> +
> +/* Non-Temporal Writes to Remote Memory */
> +#define NON_TEMP_WRITE_TO_REMOTE_MEM BIT(3)
> +
> +/* Reads to Local Memory the system identifies as "Slow Memory" */
> +#define READS_TO_LOCAL_S_MEM BIT(4)
> +
> +/* Reads to Remote Memory the system identifies as "Slow Memory" */
> +#define READS_TO_REMOTE_S_MEM BIT(5)
> +
> +/* Dirty Victims to All Types of Memory */
> +#define DIRTY_VICTIMS_TO_ALL_MEM BIT(6)
> +

Could you please fixup the comments to only capitalize
the first word of each sentence (unless it is an acronym
or required for some other reason)?

> +/* Max event bits supported */
> +#define MAX_EVT_CONFIG_BITS GENMASK(6, 0)
>
> struct rdt_fs_context {
> struct kernfs_fs_context kfc;
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index da11fdad204d..6f067c1ac7c1 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -254,8 +254,85 @@ static const struct kernfs_ops kf_mondata_ops = {
> .seq_show = rdtgroup_mondata_show,
> };
>
> +struct mon_config_info {
> + u32 evtid;
> + u32 mon_config;
> +};
> +
> +/*
> + * This is called via IPI to read the CQM/MBM counters
> + * in a domain.

This comment does not seem accurate - it is not reading the
actual counters but the configuration of the counters?

> + */
> +void mon_event_config_read(void *info)
> +{
> + struct mon_config_info *mon_info = info;
> + u32 h, msr_index;
> +
> + switch (mon_info->evtid) {
> + case QOS_L3_MBM_TOTAL_EVENT_ID:
> + msr_index = 0;
> + break;
> + case QOS_L3_MBM_LOCAL_EVENT_ID:
> + msr_index = 1;
> + break;
> + default:
> + /* Not expected to come here */
> + return;
> + }
> +
> + rdmsr(MSR_IA32_EVT_CFG_BASE + msr_index, mon_info->mon_config, h);
> +}
> +
> +void mondata_config_read(struct rdt_domain *d, struct mon_config_info *mon_info)
> +{
> + smp_call_function_any(&d->cpu_mask, mon_event_config_read, mon_info, 1);
> +}
> +
> +int rdtgroup_mondata_config_show(struct seq_file *m, void *arg)
> +{
> + struct kernfs_open_file *of = m->private;
> + struct mon_config_info mon_info;

Could you please initialize this struct? I think this is important considering
that there is an (albeit unlikely) chance that uninitialized data can be returned
to user space.

> + struct rdt_hw_resource *hw_res;
> + u32 resid, evtid, domid;
> + struct rdtgroup *rdtgrp;
> + struct rdt_resource *r;
> + union mon_data_bits md;
> + struct rdt_domain *d;
> + int ret = 0;
> +
> + rdtgrp = rdtgroup_kn_lock_live(of->kn);
> + if (!rdtgrp) {
> + ret = -ENOENT;
> + goto out;
> + }
> +
> + md.priv = of->kn->priv;
> + resid = md.u.rid;
> + domid = md.u.domid;
> + evtid = md.u.evtid;
> +
> + hw_res = &rdt_resources_all[resid];
> + r = &hw_res->r_resctrl;
> +
> + d = rdt_find_domain(r, domid, NULL);
> + if (IS_ERR_OR_NULL(d)) {
> + ret = -ENOENT;
> + goto out;
> + }
> +
> + mon_info.evtid = evtid;
> + mondata_config_read(d, &mon_info);
> +
> + seq_printf(m, "0x%x\n", mon_info.mon_config);
> +
> +out:
> + rdtgroup_kn_unlock(of->kn);
> + return ret;
> +}
> +
> static const struct kernfs_ops kf_mondata_config_ops = {
> .atomic_write_len = PAGE_SIZE,
> + .seq_show = rdtgroup_mondata_config_show,
> };

> static bool is_cpu_list(struct kernfs_open_file *of)
>
>

Reinette