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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 07EB5CCD185 for ; Fri, 10 Oct 2025 16:53:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=HqgiiZ5o5qv7rye5RH9b2UVmC+QWuqAgyTpGDi/EGkA=; b=HXELgiO2BXAykQHEXjB7G+cWSL IzcNJ0qHv67ORHy175ijmCY0exioEKIC1EQ0X3L8t/owt6sJ7SS+OKOhen1cIssOi8+dL1hAAquF4 HncZwYiaro/AuQlF0HTjDu5N4n7WjTHFAqJAkkUuc5KX5BIx12ahf1IY4mUPyeN7dcOyf3Sm7Rsvq TWpi8xT7p7jj6K5ZWmFC00SKLFi3Ux9JsjUyAQ4/foPn4R5ZA62tkmzLBFnU28cu29Y+DtB0kJiru 44XkNkEgL74YII9Li1TOw2XNjxFbd5/TX8J8K6El+gIMC9/n7LN4/LKJAEoQMbYF3ocY0ZauWaPjg EyVa86gg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7GN0-00000008zsP-477K; Fri, 10 Oct 2025 16:53:30 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7GMy-00000008zrX-0g8W for linux-arm-kernel@lists.infradead.org; Fri, 10 Oct 2025 16:53:29 +0000 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 0B9EE1596; Fri, 10 Oct 2025 09:53:19 -0700 (PDT) Received: from [10.1.197.69] (eglon.cambridge.arm.com [10.1.197.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6D3073F66E; Fri, 10 Oct 2025 09:53:21 -0700 (PDT) Message-ID: <31f11369-c6ef-4a6b-a36e-973128d8f0fd@arm.com> Date: Fri, 10 Oct 2025 17:53:19 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 27/29] arm_mpam: Add helper to reset saved mbwu state To: Jonathan Cameron Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com, David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , fenghuay@nvidia.com, baisheng.gao@unisoc.com, Rob Herring , Rohit Mathew , Rafael Wysocki , Len Brown , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , Greg Kroah-Hartman , Danilo Krummrich References: <20250910204309.20751-1-james.morse@arm.com> <20250910204309.20751-28-james.morse@arm.com> <20250912143302.00004d0e@huawei.com> Content-Language: en-GB From: James Morse In-Reply-To: <20250912143302.00004d0e@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251010_095328_321172_8290A356 X-CRM114-Status: GOOD ( 21.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Jonathan, On 12/09/2025 14:33, Jonathan Cameron wrote: > On Wed, 10 Sep 2025 20:43:07 +0000 > James Morse wrote: > >> resctrl expects to reset the bandwidth counters when the filesystem >> is mounted. >> >> To allow this, add a helper that clears the saved mbwu state. Instead >> of cross calling to each CPU that can access the component MSC to >> write to the counter, set a flag that causes it to be zero'd on the >> the next read. This is easily done by forcing a configuration update. >> >> Signed-off-by: James Morse > Minor comments inline. >> @@ -1245,6 +1257,37 @@ int mpam_msmon_read(struct mpam_component *comp, struct mon_cfg *ctx, >> return err; >> } >> >> +void mpam_msmon_reset_mbwu(struct mpam_component *comp, struct mon_cfg *ctx) >> +{ >> + int idx; >> + struct mpam_msc *msc; >> + struct mpam_vmsc *vmsc; >> + struct mpam_msc_ris *ris; >> + >> + if (!mpam_is_enabled()) >> + return; >> + >> + idx = srcu_read_lock(&mpam_srcu); > > Maybe guard() though it doesn't add that much here. 'Fixed' already based on your other feedback. >> + list_for_each_entry_rcu(vmsc, &comp->vmsc, comp_list) { > > Reason not to use _srcu variants? Typo - I'd switched it all to srcu because of the pcc thing's need to sleep, but didn't fix all these properly. >> + if (!mpam_has_feature(mpam_feat_msmon_mbwu, &vmsc->props)) >> + continue; >> + >> + msc = vmsc->msc; >> + list_for_each_entry_rcu(ris, &vmsc->ris, vmsc_list) { >> + if (!mpam_has_feature(mpam_feat_msmon_mbwu, &ris->props)) >> + continue; >> + >> + if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc))) >> + continue; >> + >> + ris->mbwu_state[ctx->mon].correction = 0; >> + ris->mbwu_state[ctx->mon].reset_on_next_read = true; >> + mpam_mon_sel_unlock(msc); >> + } >> + } >> + srcu_read_unlock(&mpam_srcu, idx); >> +} >> + >> static void mpam_reset_msc_bitmap(struct mpam_msc *msc, u16 reg, u16 wd) >> { >> u32 num_words, msb; >> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h >> index c190826dfbda..7cbcafe8294a 100644 >> --- a/drivers/resctrl/mpam_internal.h >> +++ b/drivers/resctrl/mpam_internal.h >> @@ -223,10 +223,12 @@ struct mon_cfg { >> >> /* >> * Changes to enabled and cfg are protected by the msc->lock. >> - * Changes to prev_val and correction are protected by the msc's mon_sel_lock. >> + * Changes to reset_on_next_read, prev_val and correction are protected by the >> + * msc's mon_sel_lock. > Getting close to the point where a list of one per line would reduce churn. > If you anticipate adding more to this in future I'd definitely consider it. > e.g. > * msc's mon_sel_lcok protects: > * - reset_on_next_read > * - prev_val > * - correction > */ It doesn't get expanded further, this is the last patch of the driver. But this is easier to read, so I'll do that. Thanks, James