From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3DAE6C433F5 for ; Fri, 17 Sep 2021 16:58:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24B4A6121F for ; Fri, 17 Sep 2021 16:58:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245546AbhIQQ7d (ORCPT ); Fri, 17 Sep 2021 12:59:33 -0400 Received: from foss.arm.com ([217.140.110.172]:55540 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244985AbhIQQ7R (ORCPT ); Fri, 17 Sep 2021 12:59:17 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3AB651063; Fri, 17 Sep 2021 09:57:55 -0700 (PDT) Received: from [192.168.0.14] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ED1243F99C; Fri, 17 Sep 2021 09:57:52 -0700 (PDT) From: James Morse Subject: Re: [PATCH v1 07/20] x86/resctrl: Remove architecture copy of mbps_val To: Reinette Chatre , x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, Jamie Iles , D Scott Phillips OS , lcherian@marvell.com, bobo.shaobowang@huawei.com References: <20210729223610.29373-1-james.morse@arm.com> <20210729223610.29373-8-james.morse@arm.com> Message-ID: <2dd5ef98-9734-d1c4-e165-a290b5bcd1a7@arm.com> Date: Fri, 17 Sep 2021 17:57:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Reinette, On 01/09/2021 22:26, Reinette Chatre wrote: > On 7/29/2021 3:35 PM, James Morse wrote: >> The resctrl arch code provides a second configuration array mbps_val[] >> for the mba socftware controller. > > "mba socftware" -> "MBA software" (fixed) >> Since resctrl switched over to allocating and freeing its own array >> when needed, nothing uses the arch code version. >> >> Remove it. >> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c >> index 56b3541617b5..e864dbc6fe3d 100644 >> --- a/arch/x86/kernel/cpu/resctrl/core.c >> +++ b/arch/x86/kernel/cpu/resctrl/core.c >> @@ -406,12 +406,9 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm) >>        * Initialize the Control MSRs to having no control. >>        * For Cache Allocation: Set all bits in cbm >>        * For Memory Allocation: Set b/w requested to 100% >> -     * and the bandwidth in MBps to U32_MAX >>        */ >> -    for (i = 0; i < hw_res->num_closid; i++, dc++, dm++) { >> +    for (i = 0; i < hw_res->num_closid; i++, dc++) >>           *dc = r->default_ctrl; >> -        *dm = MBA_MAX_MBPS; >> -    } > > Since this function used to reset the array to default I was expecting its callers to now > reset the new array (more below). dm/mbps_val? Its initialised when its allocated by mba_sc_domain_allocate() when the filesystem is mounted, or the domain online callback is made. >>   } >>     static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d) >> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c >> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c >> index 185f9bb992d1..297c20491549 100644 >> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c >> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c >> @@ -1906,7 +1906,7 @@ static int set_mba_sc(bool mba_sc) >>       r->membw.mba_sc = mba_sc; >>       list_for_each_entry(d, &r->domains, list) { >>           hw_dom = resctrl_to_arch_dom(d); >> -        setup_default_ctrlval(r, hw_dom->ctrl_val, hw_dom->mbps_val); >> +        setup_default_ctrlval(r, hw_dom->ctrl_val); >>       } >>   > > I am wondering why new array is not reset instead of original at this call site? set_mba_sc() doesn't need to. During mount mba_sc is set to true in rdt_enable_ctx(), which is before the mbps_val[] array is allocated. Once its allocated, its initialised. While the filesystem is mounted, and domains come and go, the array is re-allocated and re-initialised. On unmount, the array is freed when the schemata list is destroyed. I think moving the allocation/free into set_mba_sc() will make this clearer. > oh ... I > see it is removed in following patch BUT it mentions that it is ok because > reset_all_ctrls() does similar reset ... but it does not seem to do so for mbps_val. That is about the ctrl_val[] array. The reset_all_ctrls() call should reset the hardware that the arch code looks after. After these changes the mbps_val[] array is a resctrl filesystem thing that the arch code doesn't need to know anything about. Thanks, James