Re: [PATCH v6 22/22] x86/resctrl: Introduce interface to modify assignment states of the groups

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

On 8/21/24 1:11 PM, Moger, Babu wrote:
> On 8/16/24 17:33, Reinette Chatre wrote:
>> On 8/6/24 3:00 PM, Babu Moger wrote:

...

>>> +
>>> +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;
>>
>> It looks like this supports flags like "_lt", treating it as assigning
>> both local and total. I expect this should remove all flags instead?
> 
> This is a cobination of flags.
> "_lt"  This will assign both local and total.
> "lt_"  This with remove both the flags.
> 
> It seems alright to me. Do you want me to change the bahaviour here?

This looks like undefined behavior to me. A request to set individual flags
and also clear all flags looks like a contradiction to me.

> 
> 
>>
>>> +        default:
>>> +            break;
>>> +        }
>>> +    }
>>> +
>>> +    return mon_state;
>>> +}
>>
>> hmmm ... so you removed assigning mon_state to ASSIGN_NONE from default,
>> but that did not change what this function returns since ASSIGN_NONE is 0
>> and mon_state is initialized to 0. Unknown flags should cause error so
>> that it is possible to add flags in the future. Above prevents us from
>> ever adding new flags.
> 
> May be I am missing something here. How about this?
> 
> enum {
>          ASSIGN_NONE = 0,
>          ASSIGN_TOTAL,
>          ASSIGN_LOCAL,
>          ASSIGN_INVALID,
> };
> 
> 
> static int rdtgroup_str_to_mon_state(char *flag)
> {
>          int i, mon_state = ASSIGN_NONE;
> 
>          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_INVALID;
>                          goto out_done;
>                 }
>          }
> 
> :out_done:
>          return mon_state;
> }
> 
> Then handle the ASSIGN_INVALID from the caller.  Is that what you think?

Why not return an error?

> 
>>
>>> +
>>> +static struct rdtgroup *rdtgroup_find_grp(enum rdt_group_type rtype,
>>> char *p_grp, char *c_grp)
>>
>> rdtgroup_find_grp() -> rdtgroup_find_grp_by_name()?
>>
>>> +{
>>> +    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(struct rdt_resource *r,
>>> +                  enum rdt_group_type rtype,
>>> +                  char *p_grp, char *c_grp, char *tok)
>>> +{
>>> +    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, "=+-");
>>> +
>>> +    /* Check for domain id '*' which means all domains */
>>> +    if (id_str && *id_str == '*') {
>>> +        d = NULL;
>>> +        goto check_state;
>>> +    } else 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;
>>> +    }
>>> +
>>> +check_state:
>>> +    mon_state = rdtgroup_str_to_mon_state(dom_str);
>>
>> Function should return error and exit here.
> 
> No. This is case to skip checking for domain when '*' is passed to apply
> assignment to all the domains.

Using "*" for a domain still requires valid flags, no?

Reinette