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 55958F4BB6C for ; Tue, 24 Feb 2026 17:58:58 +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: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rtHbmFo2/voKLy5pRuxTgB8urATfjI3cl2qCaw0Shps=; b=DHm3EYwPJ5jcl+XRs5coU2T3EW EJC2felBTvRMZmAeox42wkI6KQCZoFIw+VqwQakgZwXhIuEXBfNDy0I3odevMUrB8b3nk+j+yX9wd ocCmFllNojuQ9sN88Fl8bhBLUlbzCZI6aEm01s24f1fvksAlDsLvTBB7oVa7eYPMqzyG2Wh0/T7Ux YCYJ3ej1vfremMxhoeQCusKeWHaj2IDPsei4tsgWmwA9cnbsEhYaeN/lG3z9STjiYryqKCHpwfKwR qTGBg6e0EjzAMxUkjyBvF92Yn+tqUd6tngyB2YLjNuQ8Ju03xjqMh954CEnqaIIAPQ8YiNIWYzUP6 RquEeYaA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vuwgH-00000002XVA-2xbS; Tue, 24 Feb 2026 17:58:45 +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 1vuwfy-00000002X5P-0zdN for linux-arm-kernel@lists.infradead.org; Tue, 24 Feb 2026 17:58:29 +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 14B6E1595; Tue, 24 Feb 2026 09:58:19 -0800 (PST) Received: from e134344.cambridge.arm.com (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 562EB3F59E; Tue, 24 Feb 2026 09:58:20 -0800 (PST) From: Ben Horgan To: ben.horgan@arm.com Cc: amitsinght@marvell.com, baisheng.gao@unisoc.com, baolin.wang@linux.alibaba.com, carl@os.amperecomputing.com, dave.martin@arm.com, david@kernel.org, dfustini@baylibre.com, fenghuay@nvidia.com, gshan@redhat.com, james.morse@arm.com, jonathan.cameron@huawei.com, kobak@nvidia.com, lcherian@marvell.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peternewman@google.com, punit.agrawal@oss.qualcomm.com, quic_jiles@quicinc.com, reinette.chatre@intel.com, rohit.mathew@arm.com, scott@os.amperecomputing.com, sdonthineni@nvidia.com, tan.shaopeng@fujitsu.com, xhao@linux.alibaba.com, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, kvmarm@lists.linux.dev, zengheng4@huawei.com, linux-doc@vger.kernel.org, Shaopeng Tan , Dave Martin Subject: [PATCH v5 10/41] arm64: mpam: Add helpers to change a task or cpu's MPAM PARTID/PMG values Date: Tue, 24 Feb 2026 17:56:49 +0000 Message-ID: <20260224175720.2663924-11-ben.horgan@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260224175720.2663924-1-ben.horgan@arm.com> References: <20260224175720.2663924-1-ben.horgan@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260224_095826_503698_77A19D29 X-CRM114-Status: GOOD ( 11.92 ) 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 From: James Morse 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. Tested-by: Gavin Shan Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Zeng Heng CC: Dave Martin Reviewed-by: Shaopeng Tan Reviewed-by: Jonathan Cameron Reviewed-by: Catalin Marinas Signed-off-by: James Morse Signed-off-by: Ben Horgan --- Changes since rfc: Keep comment attached to mpam_get_regval() Add internal helper, __mpam_regval() (Jonathan) Changes since v3: Remove extra CONFIG_ARM64_MPAM guarding Extend CONFIG_ARM64_MPAM guarding --- arch/arm64/include/asm/mpam.h | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/mpam.h b/arch/arm64/include/asm/mpam.h index 6bccbfdccb87..05aa71200f61 100644 --- a/arch/arm64/include/asm/mpam.h +++ b/arch/arm64/include/asm/mpam.h @@ -4,6 +4,7 @@ #ifndef __ASM__MPAM_H #define __ASM__MPAM_H +#include #include #include #include @@ -22,6 +23,23 @@ DECLARE_PER_CPU(u64, arm64_mpam_current); */ extern u64 arm64_mpam_global_default; +#ifdef CONFIG_ARM64_MPAM +static inline u64 __mpam_regval(u16 partid_d, u16 partid_i, u8 pmg_d, u8 pmg_i) +{ + return FIELD_PREP(MPAM0_EL1_PARTID_D, partid_d) | + FIELD_PREP(MPAM0_EL1_PARTID_I, partid_i) | + FIELD_PREP(MPAM0_EL1_PMG_D, pmg_d) | + FIELD_PREP(MPAM0_EL1_PMG_I, pmg_i); +} + +static inline void mpam_set_cpu_defaults(int cpu, u16 partid_d, u16 partid_i, + u8 pmg_d, u8 pmg_i) +{ + u64 default_val = __mpam_regval(partid_d, partid_i, pmg_d, pmg_i); + + WRITE_ONCE(per_cpu(arm64_mpam_default, cpu), default_val); +} + /* * The resctrl filesystem writes to the partid/pmg values for threads and CPUs, * which may race with reads in mpam_thread_switch(). Ensure only one of the old @@ -30,12 +48,20 @@ extern u64 arm64_mpam_global_default; * value to be stored with cache allocations, despite being considered 'free' by * resctrl. */ -#ifdef CONFIG_ARM64_MPAM static inline u64 mpam_get_regval(struct task_struct *tsk) { return READ_ONCE(task_thread_info(tsk)->mpam_partid_pmg); } +static inline void mpam_set_task_partid_pmg(struct task_struct *tsk, + u16 partid_d, u16 partid_i, + u8 pmg_d, u8 pmg_i) +{ + u64 regval = __mpam_regval(partid_d, partid_i, pmg_d, pmg_i); + + WRITE_ONCE(task_thread_info(tsk)->mpam_partid_pmg, regval); +} + static inline void mpam_thread_switch(struct task_struct *tsk) { u64 oldregval; -- 2.43.0