linux-kernel - Re: [PATCH v8 06/10] fs/resctrl: Add user interface to enable/disable io

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cfe2a26f-59a7-4563-b6a8-aaa674f60636@intel.com>
Date: Thu, 28 Aug 2025 19:47:41 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Moger, Babu" <babu.moger@....com>, <corbet@....net>,
	<tony.luck@...el.com>, <Dave.Martin@....com>, <james.morse@....com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
	<paulmck@...nel.org>, <rostedt@...dmis.org>, <Neeraj.Upadhyay@....com>,
	<david@...hat.com>, <arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
	<yosry.ahmed@...ux.dev>, <sohil.mehta@...el.com>, <xin@...or.com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <peterz@...radead.org>,
	<me@...aill.net>, <mario.limonciello@....com>, <xin3.li@...el.com>,
	<ebiggers@...gle.com>, <ak@...ux.intel.com>, <chang.seok.bae@...el.com>,
	<andrew.cooper3@...rix.com>, <perry.yuan@....com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<manali.shukla@....com>, <gautham.shenoy@....com>
Subject: Re: [PATCH v8 06/10] fs/resctrl: Add user interface to enable/disable
 io_alloc feature

Hi Babu,

On 8/27/25 1:39 PM, Moger, Babu wrote:
> On 8/22/25 17:53, Moger, Babu wrote:
>> On 8/7/2025 8:49 PM, Reinette Chatre wrote:
>>> On 8/5/25 4:30 PM, Babu Moger wrote:

>>>
>>>> +    enum resctrl_conf_type peer_type;
>>>> +    struct resctrl_schema *peer_s;
>>>> +    int ret;
>>>> +
>>>> +    rdt_staged_configs_clear();
>>>> +
>>>> +    ret = rdtgroup_init_cat(s, closid);
>>>> +    if (ret < 0)
>>>> +        goto out;
>>>> +
>>>> +    /* Initialize schema for both CDP_DATA and CDP_CODE when CDP is
>>>> enabled */
>>>> +    if (resctrl_arch_get_cdp_enabled(r->rid)) {
>>>> +        peer_type = resctrl_peer_type(s->conf_type);
>>>> +        peer_s = resctrl_get_schema(peer_type);
>>>> +        if (peer_s) {
>>>> +            ret = rdtgroup_init_cat(peer_s, closid);
>>> This is unexpected. In v7 I suggested that when parsing the CBM of one
>>> of the CDP
>>> resources it is not necessary to do so again for the peer. The CBM can be
>>> parsed *once* and the configuration just copied over. See:
>>> https://lore.kernel.org/
>>> lkml/82045638-2b26-4682-9374-1c3e400a580a@...el.com/
>>
>> Let met try to understand.
>>
>> So, rdtgroup_init_cat() sets up the staged _config for the specific CDP
>> type for all the domains.
>>
>> We need to apply those staged_configs to its peer type on all the domains.

To put it more directly, this implementation keeps the CBM of CDP_CODE and
CDP_DATA in sync. Skipping the unnecessary and duplicate parsing and instead
copying the CBM from one to the other makes that obvious.

>>
>> Something like this?
>>
>> /* Initialize staged_config of the peer type when CDP is enabled */
>>         if (resctrl_arch_get_cdp_enabled(r->rid)) {
>>                 list_for_each_entry(d, &s->res->ctrl_domains, hdr.list) {
>>                         cfg = &d->staged_config[s->conf_type];
>>                         cfg_peer = &d->staged_config[peer_type];
>>                         cfg_peer->new_ctrl = cfg->new_ctrl;
>>                         cfg_peer->have_new_ctrl = cfg->have_new_ctrl;
>>                 }
>>         }
>>
> 
> Replaced with following snippet.
> 
> /* Initialize schema for both CDP_DATA and CDP_CODE when CDP is enabled */

Could this be more specific? For example,
"Keep CDP_CODE and CDP_DATA of io_alloc CLOSID's CBM in sync."

> +	if (resctrl_arch_get_cdp_enabled(r->rid)) {
> +		peer_type = resctrl_peer_type(s->conf_type);
> +		list_for_each_entry(d, &s->res->ctrl_domains, hdr.list)
> +			memcpy(&d->staged_config[peer_type],
> +			       &d->staged_config[s->conf_type],
> +			       sizeof(*d->staged_config));

This looks good to me. To make it obvious what types are dealt with this
can instead use sizeof(d->staged_config[0]).

Thank you.

Reinette