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 2F43CD6ACE2 for ; Thu, 18 Dec 2025 10:44:48 +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:MIME-Version:References:In-Reply-To:Message-ID:Subject:CC:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=KBZ4kngHz4nSdNUr3WEEynRgoxo3LXlMcyTui2TImWE=; b=xgWRpALLFtlyaB1JFzypaEJteN Cd4G2vj3lG7zjQvoLAgT2S1nAm22NY9c2mvFqGplyqSz6v4sWu9v70zTsNPn/JCRXv1ZM6MPSdDTP rZLv/mIQyAuFLWgz1JRGCBQARiR62PlNUerG0SjMsEeiU40P0Au4hdDBYsF14iyMrd9fGClo9Fcm9 w7CusiijkOstW5HKEOqFqMbTROMyeym1oBWgDGcbPSXJOf6DgPwbRCV7/iQScvGUsLxk1qfdmq+i3 2t8Erp/HzvmCPsHyZrBsClNuGu5Y4+W2tEYWEzZ6+BVN6rLq5b7vYKrAGqZK7MyuhwoX0iz+23Tm9 MXLEMUCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWBUw-00000008FfJ-3na1; Thu, 18 Dec 2025 10:44:42 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWBUt-00000008FeH-3sXA for linux-arm-kernel@lists.infradead.org; Thu, 18 Dec 2025 10:44:41 +0000 Received: from mail.maildlp.com (unknown [172.18.224.150]) by frasgout.his.huawei.com (SkyGuard) with ESMTPS id 4dX6jN4VrfzHnGjS; Thu, 18 Dec 2025 18:44:08 +0800 (CST) Received: from dubpeml100005.china.huawei.com (unknown [7.214.146.113]) by mail.maildlp.com (Postfix) with ESMTPS id 9B04740539; Thu, 18 Dec 2025 18:44:35 +0800 (CST) Received: from localhost (10.203.177.15) by dubpeml100005.china.huawei.com (7.214.146.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.36; Thu, 18 Dec 2025 10:44:34 +0000 Date: Thu, 18 Dec 2025 10:44:33 +0000 From: Jonathan Cameron To: James Morse CC: , , D Scott Phillips OS , , , , , , Jamie Iles , "Xin Hao" , , , , David Hildenbrand , Dave Martin , Koba Ko , Shanker Donthineni , , , Gavin Shan , Ben Horgan , , , Punit Agrawal Subject: Re: [RFC PATCH 05/38] arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG values Message-ID: <20251218104433.00002196@huawei.com> In-Reply-To: <20251205215901.17772-6-james.morse@arm.com> References: <20251205215901.17772-1-james.morse@arm.com> <20251205215901.17772-6-james.morse@arm.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100011.china.huawei.com (7.191.174.247) To dubpeml100005.china.huawei.com (7.214.146.113) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251218_024440_254038_487350DB X-CRM114-Status: GOOD ( 18.18 ) 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 On Fri, 5 Dec 2025 21:58:28 +0000 James Morse wrote: > Care must be taken when modifying the PARTID and PMG of a task in any > per-task structure as writing these values may race with the task being > scheduled in, and reading the modified values. > > Add helpers to set the task properties, and the CPU default value. > These use WRITE_ONCE() that pairs with the READ_ONCE() in mpam_get_regval() > to avoid causing torn values. > > CC: Dave Martin > CC: Ben Horgan > Signed-off-by: James Morse > --- > arch/arm64/include/asm/mpam.h | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h > index 86a55176f884..2960ffaf6574 100644 > --- a/arch/arm64/include/asm/mpam.h > +++ b/arch/arm64/include/asm/mpam.h > @@ -5,6 +5,7 @@ > #define __ASM__MPAM_H > > #include > +#include > #include > #include > #include > @@ -37,6 +38,35 @@ extern u64 arm64_mpam_global_default; > * A value in struct thread_info is used instead of struct task_struct as the > * cpu's u64 register format is used, but struct task_struct has two u32'. > */ I'd be tempted to reorder this so the comment ends up near at least one use of task_thread_info(tsk)->mpam_partid_pmg. Otherwise it is even less obvious what it is referring to. Easiest might be to put the mpam_get_regval() before the mpam_set_task_partid_pmg() > +static inline void mpam_set_cpu_defaults(int cpu, u16 partid_d, u16 partid_i, > + u8 pmg_d, u8 pmg_i) > +{ > + u64 default_val; > + > + default_val = FIELD_PREP(MPAM0_EL1_PARTID_D, partid_d); > + default_val |= FIELD_PREP(MPAM0_EL1_PARTID_I, partid_i); > + default_val |= FIELD_PREP(MPAM0_EL1_PMG_D, pmg_d); > + default_val |= FIELD_PREP(MPAM0_EL1_PMG_I, pmg_i); > + > + WRITE_ONCE(per_cpu(arm64_mpam_default, cpu), default_val); > +} > + > +static inline void mpam_set_task_partid_pmg(struct task_struct *tsk, > + u16 partid_d, u16 partid_i, > + u8 pmg_d, u8 pmg_i) > +{ > +#ifdef CONFIG_ARM64_MPAM > + u64 regval; > + > + regval = FIELD_PREP(MPAM0_EL1_PARTID_D, partid_d); > + regval |= FIELD_PREP(MPAM0_EL1_PARTID_I, partid_i); > + regval |= FIELD_PREP(MPAM0_EL1_PMG_D, pmg_d); > + regval |= FIELD_PREP(MPAM0_EL1_PMG_I, pmg_i); Maybe a macro or helper to build regval given this replicates the block in mpam_set_cpu_defaults. Obviously ignore if this changes in later patches! > + > + WRITE_ONCE(task_thread_info(tsk)->mpam_partid_pmg, regval); > +#endif > +} > + > static inline u64 mpam_get_regval(struct task_struct *tsk) > { > #ifdef CONFIG_ARM64_MPAM