From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A3BD62FB99D; Fri, 10 Oct 2025 16:53:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760115209; cv=none; b=WKNe4xx0MhIKld3FPwm04LMBkOmm6vOuRydcvE/k4UFJ/1jOWv/9dA86+K/MnUjuoZlfEB6RylJ78Su4sTn0/2YllDtjdd1Zelb/xrL3k3oWYATcLXvcSF/YVppNXW6YaB/v7Gi/9eYpHqAN6VymQ4K7elq7N9WlpWfsOwkSA28= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760115209; c=relaxed/simple; bh=OLzINQnM3CK/H4My4nDZ44YiZjxfmY4mZ0yqqdG5lx0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=u00xeEUavgkeaz9JwmnucDMLOseRxkup+0CuRtlrWuMp9H+1AbJCDMafCOdML1DlrKkP3aHX+ypNTS/ByZrDLRWUTh3jHCJimLv7h4rKe8pC0Kx4dJ/eRXcVeqC+nqdbwC3AqeDbc6dI30+wNlV1WoMTNqG8x1KoxUcwwhjYAvM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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