Re: [PATCH v5 20/20] x86/resctrl: Introduce interface to modify assignment states of the groups

Reinette Chatre
2024-07-12T22:17:43Z

Hi Babu,

On 7/3/24 2:48 PM, Babu Moger wrote:
> Introduce the interface to enable events in ABMC mode.

As mentioned in cover letter, please take care with terms. This
interface does not "enable events" - note that events can be
"enabled" even in legacy mode. This is the interface to
assign counters.

>
> Events can be enabled or disabled by writing to file
> /sys/fs/resctrl/info/L3_MON/mbm_control
>
> Format is similar to the list format with addition of op-code for the
> assignment operation.
> "<CTRL_MON group>/<MON group>/<op-code><flags>"

Missing a "domain_id".

>
> Format for specific type of groups:
>
> * Default CTRL_MON group:
> "//<domain_id><op-code><flags>"
>
> * Non-default CTRL_MON group:
> "<CTRL_MON group>//<domain_id><op-code><flags>"
>
> * Child MON group of default CTRL_MON group:
> "/<MON group>/<domain_id><op-code><flags>"
>
> * Child MON group of non-default CTRL_MON group:
> "<CTRL_MON group>/<MON group>/<domain_id><op-code><flags>"
>
> Op-code can be one of the following:
>
> = Update the assignment to match the flags
> + enable a new state
> - disable a new state

(note comment in cover letter about consistent terms)

>
> Assignment flags can be one of the following:
> t MBM total event is enabled
> l MBM local event is enabled
> tl Both total and local MBM events are enabled
> _ None of the MBM events are enabled. Valid only with '=" opcode.
>
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> v5: Interface name changed from mbm_assign_control to mbm_control.
> Fixed opcode and flags combination.
> '=_" is valid.
> "-_" amd "+_" is not valid.
> Minor message update.
> Renamed the function with prefix - rdtgroup_.
> Corrected few documentation mistakes.
> Rebase related changes after SNC support.
>
> v4: Added domain specific assignments. Fixed the opcode parsing.
>
> v3: New patch.
> Addresses the feedback to provide the global assignment interface.
> https://lore.kernel.org/lkml/c73f444b-83a1-4e9a-95d3-54c5165ee782@intel.com/
> ---
> Documentation/arch/x86/resctrl.rst | 81 +++++++-
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 250 ++++++++++++++++++++++++-
> 2 files changed, 329 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 05fee779e109..5a621235eb2b 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -331,7 +331,7 @@ with the following files:
> t MBM total event is enabled.
> l MBM local event is enabled.
> tl Both total and local MBM events are enabled.
> - _ None of the MBM events are enabled.
> + _ None of the MBM events are enabled. Only works with opcode '=' for write.
>
> Examples:
> ::
> @@ -358,6 +358,85 @@ with the following files:
>
> /child_default_mon_grp/ - This is a child monitor group of default CTRL_MON group.
>
> + Assignment state can be updated by writing to the interface.
> +
> + Format is similar to the list format with addition of op-code for the
> + assignment operation.
> +
> + "<CTRL_MON group>/<MON group>/<op-code><flags>"

Missing domain_id

> +
> + Format for each type of groups:
> +
> + * Default CTRL_MON group:
> + "//<domain_id><op-code><flags>"
> +
> + * Non-default CTRL_MON group:
> + "<CTRL_MON group>//<domain_id><op-code><flags>"
> +
> + * Child MON group of default CTRL_MON group:
> + "/<MON group>/<domain_id><op-code><flags>"
> +
> + * Child MON group of non-default CTRL_MON group:
> + "<CTRL_MON group>/<MON group>/<domain_id><op-code><flags>"
> +
> + Op-code can be one of the following:
> + ::
> +
> + = Update the assignment to match the flags.
> + + Add a new state.
> + - delete a new state.
> +
> + Examples:
> + ::
> +
> + Initial group status:
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_control
> + non_default_ctrl_mon_grp//0=tl;1=tl;
> + non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> + //0=tl;1=tl;
> + /child_default_mon_grp/0=tl;1=tl;
> +
> + To update the default group to enable only total event on domain 0:
> + # echo "//0=t" > /sys/fs/resctrl/info/L3_MON/mbm_control
> +
> + Assignment status after the update:
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_control
> + non_default_ctrl_mon_grp//0=tl;1=tl;
> + non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> + //0=t;1=tl;
> + /child_default_mon_grp/0=tl;1=tl;
> +
> + To update the MON group child_default_mon_grp to remove total event on domain 1:
> + # echo "/child_default_mon_grp/1-t" > /sys/fs/resctrl/info/L3_MON/mbm_control
> +
> + Assignment status after the update:
> + $ cat /sys/fs/resctrl/info/L3_MON/mbm_control
> + non_default_ctrl_mon_grp//0=tl;1=tl;
> + non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> + //0=t;1=tl;
> + /child_default_mon_grp/0=tl;1=l;
> +
> + To update the MON group non_default_ctrl_mon_grp/child_non_default_mon_grp to
> + remove both local and total events on domain 1:
> + # echo "non_default_ctrl_mon_grp/child_non_default_mon_grp/1=_" >
> + /sys/fs/resctrl/info/L3_MON/mbm_control
> +
> + Assignment status after the update:
> + non_default_ctrl_mon_grp//0=tl;1=tl;
> + non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=_;
> + //0=t;1=tl;
> + /child_default_mon_grp/0=tl;1=l;
> +
> + To update the default group to add a local event domain 0.
> + # echo "//0+l" > /sys/fs/resctrl/info/L3_MON/mbm_control
> +
> + Assignment status after the update:
> + # cat /sys/fs/resctrl/info/L3_MON/mbm_control
> + non_default_ctrl_mon_grp//0=tl;1=tl;
> + non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=_;
> + //0=tl;1=tl;
> + /child_default_mon_grp/0=tl;1=l;
> +
> "max_threshold_occupancy":
> Read/write file provides the largest value (in
> bytes) at which a previously used LLC_occupancy
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 0de9f23d5389..84c0874d7872 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1068,6 +1068,253 @@ static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
> return 0;
> }
>
> +static int rdtgroup_str_to_mon_state(char *flag)
> +{
> + int i, mon_state = 0;
> +
> + for (i = 0; i < strlen(flag); i++) {
> + switch (*(flag + i)) {
> + case 't':
> + mon_state |= ASSIGN_TOTAL;
> + break;
> + case 'l':
> + mon_state |= ASSIGN_LOCAL;
> + break;
> + case '_':
> + mon_state = ASSIGN_NONE;
> + break;
> + default:
> + mon_state = ASSIGN_NONE;
> + break;
> + }
> + }
> +

No. As I mentioned before this makes all this work for nothing
by preventing us from ever adding another flag. Please do not
have a default catchall that unassigns all flags.

> + return mon_state;
> +}
> +
> +static struct rdtgroup *rdtgroup_find_grp(enum rdt_group_type rtype, char *p_grp, char *c_grp)
> +{
> + struct rdtgroup *rdtg, *crg;
> +
> + if (rtype == RDTCTRL_GROUP && *p_grp == '\0') {
> + return &rdtgroup_default;
> + } else if (rtype == RDTCTRL_GROUP) {
> + list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list)
> + if (!strcmp(p_grp, rdtg->kn->name))
> + return rdtg;
> + } else if (rtype == RDTMON_GROUP) {
> + list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
> + if (!strcmp(p_grp, rdtg->kn->name)) {
> + list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
> + mon.crdtgrp_list) {
> + if (!strcmp(c_grp, crg->kn->name))
> + return crg;
> + }
> + }
> + }
> + }
> +
> + return NULL;
> +}
> +
> +static int rdtgroup_process_flags(enum rdt_group_type rtype, char *p_grp, char *c_grp, char *tok)
> +{
> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> + int op, mon_state, assign_state, unassign_state;
> + char *dom_str, *id_str, *op_str;
> + struct rdt_mon_domain *d;
> + struct rdtgroup *rdtgrp;
> + unsigned long dom_id;
> + int ret, found = 0;
> +
> + rdtgrp = rdtgroup_find_grp(rtype, p_grp, c_grp);
> +
> + if (!rdtgrp) {
> + rdt_last_cmd_puts("Not a valid resctrl group\n");
> + return -EINVAL;
> + }
> +
> +next:
> + if (!tok || tok[0] == '\0')
> + return 0;
> +
> + /* Start processing the strings for each domain */
> + dom_str = strim(strsep(&tok, ";"));
> +
> + op_str = strpbrk(dom_str, "=+-");
> +
> + if (op_str) {
> + op = *op_str;
> + } else {
> + rdt_last_cmd_puts("Missing operation =, +, -, _ character\n");
> + return -EINVAL;
> + }
> +
> + id_str = strsep(&dom_str, "=+-");
> +
> + if (!id_str || kstrtoul(id_str, 10, &dom_id)) {
> + rdt_last_cmd_puts("Missing domain id\n");
> + return -EINVAL;
> + }
> +
> + /* Verify if the dom_id is valid */
> + list_for_each_entry(d, &r->mon_domains, hdr.list) {
> + if (d->hdr.id == dom_id) {
> + found = 1;
> + break;
> + }
> + }
> + if (!found) {
> + rdt_last_cmd_printf("Invalid domain id %ld\n", dom_id);
> + return -EINVAL;
> + }
> +
> + mon_state = rdtgroup_str_to_mon_state(dom_str);
> +
> + assign_state = 0;
> + unassign_state = 0;
> +
> + switch (op) {
> + case '+':
> + if (mon_state == ASSIGN_NONE) {
> + rdt_last_cmd_puts("Invalid assign opcode\n");
> + goto out_fail;
> + }
> + assign_state = mon_state;
> + break;
> + case '-':
> + if (mon_state == ASSIGN_NONE) {
> + rdt_last_cmd_puts("Invalid assign opcode\n");
> + goto out_fail;
> + }
> + unassign_state = mon_state;
> + break;
> + case '=':
> + assign_state = mon_state;
> + unassign_state = (ASSIGN_TOTAL | ASSIGN_LOCAL) & ~assign_state;
> + break;
> + default:
> + break;
> + }
> +

this flow is not clear to me ... I see how an existing counter is
configured but I do not see any counter being freed/allocated, where is that
done?

> + if (assign_state & ASSIGN_TOTAL)
> + ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_TOTAL_EVENT_ID,
> + rdtgrp->mon.rmid,
> + rdtgrp->mon.cntr_id[0],
> + rdtgrp->closid, 1);
> + if (ret)
> + goto out_fail;
> +
> + if (assign_state & ASSIGN_LOCAL)
> + ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_LOCAL_EVENT_ID,
> + rdtgrp->mon.rmid,
> + rdtgrp->mon.cntr_id[1],
> + rdtgrp->closid, 1);
> +
> + if (ret)
> + goto out_fail;
> +
> + if (unassign_state & ASSIGN_TOTAL)
> + ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_TOTAL_EVENT_ID,
> + rdtgrp->mon.rmid,
> + rdtgrp->mon.cntr_id[0],
> + rdtgrp->closid, 0);
> +
> + if (ret)
> + goto out_fail;
> +
> + if (unassign_state & ASSIGN_LOCAL)
> + ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_LOCAL_EVENT_ID,
> + rdtgrp->mon.rmid,
> + rdtgrp->mon.cntr_id[1],
> + rdtgrp->closid, 0);
> + if (ret)
> + goto out_fail;
> +
> + goto next;
> +
> +out_fail:
> +
> + return -EINVAL;
> +}
> +
> +static ssize_t rdtgroup_mbm_control_write(struct kernfs_open_file *of,
> + char *buf, size_t nbytes,
> + loff_t off)
> +{
> + struct rdt_resource *r = of->kn->parent->priv;
> + char *token, *cmon_grp, *mon_grp;
> + struct rdt_hw_resource *hw_res;
> + int ret;
> +
> + hw_res = resctrl_to_arch_res(r);
> + if (!hw_res->abmc_enabled)
> + return -EINVAL;
> +
> + /* Valid input requires a trailing newline */
> + if (nbytes == 0 || buf[nbytes - 1] != '\n')
> + return -EINVAL;
> +
> + buf[nbytes - 1] = '\0';
> + rdt_last_cmd_clear();

rdt_last_cmd_clear() should be called with mutex held

> +
> + cpus_read_lock();
> + mutex_lock(&rdtgroup_mutex);
> +
> + while ((token = strsep(&buf, "\n")) != NULL) {
> + if (strstr(token, "//")) {
> + /*
> + * The CTRL_MON group processing:
> + * default CTRL_MON group: "//<flags>"
> + * non-default CTRL_MON group: "<CTRL_MON group>//flags"
> + * The CTRL_MON group will be empty string if it is a
> + * default group.
> + */
> + cmon_grp = strsep(&token, "//");
> +
> + /*
> + * strsep returns empty string for contiguous delimiters.
> + * Make sure check for two consicutive delimiters and

consicutive -> consecutive

> + * advance the token.
> + */
> + mon_grp = strsep(&token, "//");
> + if (*mon_grp != '\0') {
> + rdt_last_cmd_printf("Invalid CTRL_MON group format %s\n", token);
> + ret = -EINVAL;
> + break;
> + }
> +
> + ret = rdtgroup_process_flags(RDTCTRL_GROUP, cmon_grp, mon_grp, token);
> + if (ret)
> + break;
> + } else if (strstr(token, "/")) {
> + /*
> + * MON group processing:
> + * MON_GROUP inside default CTRL_MON group: "/<MON group>/<flags>"
> + * MON_GROUP within CTRL_MON group: "<CTRL_MON group>/<MON group>/<flags>"
> + */
> + cmon_grp = strsep(&token, "/");
> +
> + /* Extract the MON_GROUP. It cannot be empty string */
> + mon_grp = strsep(&token, "/");
> + if (*mon_grp == '\0') {
> + rdt_last_cmd_printf("Invalid MON_GROUP format %s\n", token);
> + ret = -EINVAL;
> + break;
> + }
> +
> + ret = rdtgroup_process_flags(RDTMON_GROUP, cmon_grp, mon_grp, token);
> + if (ret)
> + break;
> + }

can these two blocks not be merged? strsep(&token, "//") and strsep(&token, "/") do the same
thing, no?

> + }
> +
> + mutex_unlock(&rdtgroup_mutex);
> + cpus_read_unlock();
> +
> + return ret ?: nbytes;
> +}
> +
> #ifdef CONFIG_PROC_CPU_RESCTRL
>
> /*
> @@ -2282,9 +2529,10 @@ static struct rftype res_common_files[] = {
> },
> {
> .name = "mbm_control",
> - .mode = 0444,
> + .mode = 0644,
> .kf_ops = &rdtgroup_kf_single_ops,
> .seq_show = rdtgroup_mbm_control_show,
> + .write = rdtgroup_mbm_control_write,
> },
> {
> .name = "cpus_list",

Reinette