linux-kernel - Re: [RFC 09/12] fs/resctrl: Extend schemata write for priority partition control

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Message-ID: <944e7e64-509b-c916-5166-13e7bfe2161b@intel.com>
Date:   Thu, 17 Aug 2023 10:27:42 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Amit Singh Tomar <amitsinght@...vell.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <reinette.chatre@...el.com>, <james.morse@....com>,
        <gcherian@...vell.com>, <robh@...nel.org>, <peternewman@...gle.com>
Subject: Re: [RFC 09/12] fs/resctrl: Extend schemata write for priority
 partition control

Hi, Amit,

On 8/15/23 08:27, Amit Singh Tomar wrote:
> Currently, Users can pass the configurations for CPBM, and MBA through
> schemata file. For instance, CPBM can be passed using:
> 
> echo L3:0=ffff > schemata
> 
> This change allows, users to pass a new configuration for downstream
> priority along with CPBM. For instance, dspri value of "0xa" can be
> passed as:
> 
> echo L3:0=ffff,a > schemata
> 
> Signed-off-by: Amit Singh Tomar <amitsinght@...vell.com>
> ---
>   fs/resctrl/ctrlmondata.c | 92 ++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 92 insertions(+)
> 
> diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
> index ffeb68270968..b444adee2002 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -30,6 +30,74 @@ typedef int (ctrlval_parser_t)(struct rdt_parse_data *data,
>   			       struct resctrl_schema *s,
>   			       struct rdt_domain *d);
>   
> +static bool dspri_validate(char *buf, unsigned long *data, struct rdt_resource *r)
> +{
> +
> +	char *dup_buf, *dspri_token;
> +	unsigned long dspri_val;
> +	bool success = true;
> +	int ret;
> +
> +	dup_buf = kstrdup(buf, GFP_KERNEL);
> +	if (!dup_buf) {
> +		rdt_last_cmd_printf("Failed to allocate buffer %s\n",
> +					__func__);
> +		success = false;
> +		goto out;
> +	}
> +
> +	strsep(&dup_buf, ",");
> +	if (!dup_buf) {
> +		rdt_last_cmd_printf("Unable to find priority value token %s\n",
> +					__func__);
> +		success = false;
> +		goto out;
> +	}
> +
> +	dspri_token = strsep(&dup_buf, ",");
> +	ret = kstrtoul(dspri_token, 16, &dspri_val);
> +	if (ret) {
> +		rdt_last_cmd_printf("Non-hex character in the mask %s\n", buf);
> +		success = false;
> +		goto out;
> +	}
> +
> +	if (dspri_val > r->dspri_default_ctrl) {
> +		rdt_last_cmd_printf("dspri value %ld out of range [%d-%d]\n", dspri_val,
> +					0, r->dspri_default_ctrl);
> +		success = false;
> +		goto out;
> +	}
> +
> +	*data = dspri_val;
> +
> +out:
> +	kfree(dup_buf);
> +	return success;
> +}
> +
> +static int parse_dspri(struct rdt_parse_data *data, struct resctrl_schema *s,
> +			struct rdt_domain *d)
> +{
> +	struct resctrl_staged_config *cfg;
> +	struct rdt_resource *r = s->res;
> +	unsigned long pri_val;
> +
> +	cfg = &d->staged_config[s->conf_type];
> +	if (cfg->have_new_ctrl) {
> +		rdt_last_cmd_printf("Duplicate domain %d\n", d->id);
> +		return -EINVAL;
> +	}
> +
> +	if (!dspri_validate(data->buf, &pri_val, r))
> +		return -EINVAL;
> +
> +	cfg->new_ctrl = pri_val;
> +	cfg->have_new_ctrl = true;
> +
> +	return 0;
> +}
> +
>   /*
>    * Check whether MBA bandwidth percentage value is correct. The value is
>    * checked against the minimum and max bandwidth values specified by the
> @@ -293,6 +361,8 @@ static int rdtgroup_parse_resource(char *resname, char *tok,
>   ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
>   				char *buf, size_t nbytes, loff_t off)
>   {
> +	char *dup_buf = kstrdup(buf, GFP_KERNEL);
> +	struct rdt_parse_data data;
>   	struct resctrl_schema *s;
>   	struct rdtgroup *rdtgrp;
>   	struct rdt_domain *dom;
> @@ -354,10 +424,32 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
>   		if (is_mba_sc(r))
>   			continue;
>   
> +		if (r->priority_cap)
> +			r->dspri_store = false;
> +
>   		if (!strcmp(resname, s->name)) {
>   			ret = resctrl_arch_update_domains(r, rdtgrp->closid);
>   			if (ret)
>   				goto out;
> +
> +			if (r->priority_cap) {
> +				r->dspri_store = true;
> +				list_for_each_entry(dom, &r->domains, list) {
> +					ctrlval_parser_t *parse_ctrlval = &parse_dspri;
> +					char *dom_data = NULL;
> +
> +					dom_data = strsep(&dup_buf, ";");
> +					dom_data = strim(dom_data);
> +					data.buf = dom_data;
> +					data.rdtgrp = rdtgrp;
> +					if (parse_ctrlval(&data, s, dom))

Can this parse be called within parse_line()? So parsing and validation 
are before real write. If any parsing error, no write. Otherwise, 
partial write or roll back may happen.

> +						return -EINVAL;
> +				}
> +
> +				ret = resctrl_arch_update_domains(r, rdtgrp->closid);
> +				if (ret)
> +					goto out;

r->dspri_store = false here?

> +			}
>   		}
>   	}
>   

Thanks.

-Fenghua