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SubjectRE: [PATCH 30/32] x86/intel_rdt_rdtgroup.c: Process schemas input from rscctrl interface
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> From: David Carrillo-Cisneros [mailto:davidcc@google.com]
> > +static int get_res_type(char **res, enum resource_type *res_type) {
> > + char *tok;
> > +
> > + tok = strsep(res, ":");
> > + if (tok == NULL)
> > + return -EINVAL;
> > +
> > + if (!strcmp(tok, "L3")) {
>
> Maybe use strstrip to allow a more readable input ? i.e. "L3 : <schema> "


>
> > + *res_type = RESOURCE_L3;
> > + return 0;
> > + }
> > +
> > + return -EINVAL;
> > +}
> > +
> > +static int divide_resources(char *buf, char *resources[RESOURCE_NUM])
> > +{
> > + char *tok;
> > + unsigned int resource_num = 0;
> > + int ret = 0;
> > + char *res;
> > + char *res_block;
> > + size_t size;
> > + enum resource_type res_type;
> > +
> > + size = strlen(buf) + 1;
> > + res = kzalloc(size, GFP_KERNEL);
> > + if (!res) {
> > + ret = -ENOSPC;
>
> -ENOMEM?

Will change to -ENOMEM.

>
> > +
> > + res_block = res;
> > + ret = get_res_type(&res_block, &res_type);
> > + if (ret) {
> > + pr_info("Unknown resource type!");
> > + goto out;
> > + }
>
> does this work if res_block doesn't have ":"? don't you need to check
> res_block?

get_res_type() checks ":" and return -EINVAL if no ":".

>
> > +static int get_cache_schema(char *buf, struct cache_resource *l, int level,
> > + struct rdtgroup *rdtgrp) {
> > + char *tok, *tok_cache_id;
> > + int ret;
> > + int domain_num;
> > + int input_domain_num;
> > + int len;
> > + unsigned int input_cache_id;
> > + unsigned int cid;
> > + unsigned int leaf;
> > +
> > + if (!cat_enabled(level) && strcmp(buf, ";")) {
> > + pr_info("Disabled resource should have empty schema\n");
> > + return -EINVAL;
> > + }
> > +
> > + len = strlen(buf);
> > + /*
> > + * Translate cache id based cbm from one line string with format
> > + * "<cache prefix>:<cache id0>=xxxx;<cache id1>=xxxx;..." for
> > + * disabled cdp.
> > + * Or
> > + * "<cache prefix>:<cache id0>=xxxxx,xxxxx;<cache
> id1>=xxxxx,xxxxx;..."
> > + * for enabled cdp.
> > + */
> > + input_domain_num = 0;
> > + while ((tok = strsep(&buf, ";")) != NULL) {
> > + tok_cache_id = strsep(&tok, "=");
> > + if (tok_cache_id == NULL)
> > + goto cache_id_err;
>
> what if no "=" ? , also would be nice to allow spaces around "=" .

Without "=-", reports id error. Sure I can strip the spaces around "=".

>
> > +
> > + ret = kstrtouint(tok_cache_id, 16, &input_cache_id);
> > + if (ret)
> > + goto cache_id_err;
> > +
> > + leaf = level_to_leaf(level);
>
> why is this in the loop?

Leaf is the cache index number which is contiguous starting from 0. We need to save and get
cache id info from cache index.

<leaf, cache id> uniquely identifies a cache.

Architecturally level can not be used to identify a cache. There could be 2 caches in one level, ie. icache and dcache.

So we need to translate from level
>
> > + cid = cache_domains[leaf].shared_cache_id[input_domain_num];
> > + if (input_cache_id != cid)
> > + goto cache_id_err;
>
> so schemata must be present for all cache_id's and sorted in increasing order
> of cache_id? what's the point of having the cache_id# then?

Cache_id may be not be contiguous. It can not be used directly as array index.
For user interface, user inputs cache_id to identify a cache. Internally kernel uses
domain, which is contiguous and used as index for internally saved cbm. Kernel
interface code does the mapping between cache_id and domain number.

>
> > +
> > +/*
> > + * Check if the reference counts are all ones in rdtgrp's domain.
> > + */
> > +static bool one_refcnt(struct rdtgroup *rdtgrp, int domain) {
> > + int refcnt;
> > + int closid;
> > +
> > + closid = rdtgrp->resource.closid[domain];
> > + if (cat_l3_enabled) {
>
> if cat_l3_enabled == false, then reference counts are always one?

I can change to return false if cat_l3_enabled==false.

>
> > + * Go through all shared domains. Check if there is an existing
> > +closid
> > + * in all rdtgroups that matches l3 cbms in the shared
> > + * domain. If find one, reuse the closid. Otherwise, allocate a new one.
> > + */
> > +static int get_rdtgroup_resources(struct resources *resources_set,
> > + struct rdtgroup *rdtgrp) {
> > + struct cache_resource *l3;
> > + bool l3_cbm_found;
> > + struct list_head *l;
> > + struct rdtgroup *r;
> > + u64 cbm;
> > + int rdt_closid[MAX_CACHE_DOMAINS];
> > + int rdt_closid_type[MAX_CACHE_DOMAINS];
> > + int domain;
> > + int closid;
> > + int ret;
> > +
> > + l3 = resources_set->l3;
>
> l3 is NULL if cat_l3_enabled == false but it seems like it may be used later
> even though.


>
> > + memcpy(rdt_closid, rdtgrp->resource.closid,
> > + shared_domain_num * sizeof(int));
> > + for (domain = 0; domain < shared_domain_num; domain++) {
> > + if (rdtgrp->resource.valid) {
> > + /*
> > + * If current rdtgrp is the only user of cbms in
> > + * this domain, will replace the cbms with the input
> > + * cbms and reuse its own closid.
> > + */
> > + if (one_refcnt(rdtgrp, domain)) {
> > + closid = rdtgrp->resource.closid[domain];
> > + rdt_closid[domain] = closid;
> > + rdt_closid_type[domain] = REUSED_OWN_CLOSID;
> > + continue;
> > + }
> > +
> > + l3_cbm_found = true;
> > +
> > + if (cat_l3_enabled)
> > + l3_cbm_found = cbm_found(l3, rdtgrp, domain,
> > +
> > + CACHE_LEVEL3);
> > +
> > + /*
> > + * If the cbms in this shared domain are already
> > + * existing in current rdtgrp, record the closid
> > + * and its type.
> > + */
> > + if (l3_cbm_found) {
> > + closid = rdtgrp->resource.closid[domain];
> > + rdt_closid[domain] = closid;
> > + rdt_closid_type[domain] =
> > + CURRENT_CLOSID;
>
> a new l3 resource will be created if cat_l3_enabled is false.

This code actually handles both l3 and l2.

L2 patches will be sent out later on top of this patch set.

With this patch set alone, when l3 is disabled, we will not come
to this function because initialization will fail and there is no
rscctrl file system.

>
>
> > +static void init_cache_resource(struct cache_resource *l) {
> > + l->cbm = NULL;
> > + l->cbm2 = NULL;
>
> is cbm2 the data bitmask for when CDP is enabled? if so, a more descriptive
> name may help.

Yes, that's right. It's the second CBM when CDP is enabled. Maybe I change
to a nicer name.

>
> > + l->closid = NULL;
> > + l->refcnt = NULL;
> > +}
> > +
> > +static void free_cache_resource(struct cache_resource *l) {
> > + kfree(l->cbm);
> > + kfree(l->cbm2);
> > + kfree(l->closid);
> > + kfree(l->refcnt);
>
> this function is used to clean up alloc_cache_resource in the error path of
> get_resources where it's not necessarily true that all of l's members were
> allocated.

As Thomas already said, kfree(NULL) is safe. Don't need to check pointer
before kfree() and code is short.

Thanks.

-Fenghua
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