From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.4 35/80] iommu/arm-smmu-v3: Use explicit mb() when moving cons pointer Date: Mon, 28 Jan 2019 11:23:16 -0500 Message-ID: <20190128162401.58841-35-sashal@kernel.org> References: <20190128162401.58841-1-sashal@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190128162401.58841-1-sashal-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Sasha Levin , Robin Murphy , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Will Deacon List-Id: iommu@lists.linux-foundation.org From: Will Deacon [ Upstream commit a868e8530441286342f90c1fd9c5f24de3aa2880 ] After removing an entry from a queue (e.g. reading an event in arm_smmu_evtq_thread()) it is necessary to advance the MMIO consumer pointer to free the queue slot back to the SMMU. A memory barrier is required here so that all reads targetting the queue entry have completed before the consumer pointer is updated. The implementation of queue_inc_cons() relies on a writel() to complete the previous reads, but this is incorrect because writel() is only guaranteed to complete prior writes. This patch replaces the call to writel() with an mb(); writel_relaxed() sequence, which gives us the read->write ordering which we require. Cc: Robin Murphy Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- drivers/iommu/arm-smmu-v3.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index fc6eb752ab35..eb9937225d64 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -683,7 +683,13 @@ static void queue_inc_cons(struct arm_smmu_queue *q) u32 cons = (Q_WRP(q, q->cons) | Q_IDX(q, q->cons)) + 1; q->cons = Q_OVF(q, q->cons) | Q_WRP(q, cons) | Q_IDX(q, cons); - writel(q->cons, q->cons_reg); + + /* + * Ensure that all CPU accesses (reads and writes) to the queue + * are complete before we update the cons pointer. + */ + mb(); + writel_relaxed(q->cons, q->cons_reg); } static int queue_sync_prod(struct arm_smmu_queue *q) -- 2.19.1 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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 4A283C282C8 for ; Mon, 28 Jan 2019 16:37:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0FE6120811 for ; Mon, 28 Jan 2019 16:37:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548693421; bh=L/z9AzkPPCaSA0RgojVr+F08SP13FjSvuaXE2YjmIwk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=iR5KwBy6w88S6obdtvG75vmzfbBYxQzGwcl0xsJDL5WwjfFwsfD26wswYE7WvegVD lt4yAojFXxqsM+EQoF2kuzgJorfH3uNmbdv+l7w//CWLGl+AGVl7lfYIxkU55HMZS0 whEVxMpSp44ZxKsFi9rDNZgyWulecGcBY5h47Yg4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389871AbfA1QZL (ORCPT ); Mon, 28 Jan 2019 11:25:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:33798 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389833AbfA1QZB (ORCPT ); Mon, 28 Jan 2019 11:25:01 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F2AC32171F; Mon, 28 Jan 2019 16:24:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548692700; bh=L/z9AzkPPCaSA0RgojVr+F08SP13FjSvuaXE2YjmIwk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DUtpqbY+5rCec9vN3P5UZozg11+KV/lbwQAitDIiNQ6WJ4V6BPsouRHilfj0CR6hh eVbqQB5zW57A/HfiiRvdUp6AyPU/AepsROcmlDaUzFJQhO5e7RGmCESRox+hgRDlo1 53l45+38hYtmftyO8CHAUra9u3f5lwbR9xnItSdY= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Will Deacon , Robin Murphy , Sasha Levin , iommu@lists.linux-foundation.org Subject: [PATCH AUTOSEL 4.4 35/80] iommu/arm-smmu-v3: Use explicit mb() when moving cons pointer Date: Mon, 28 Jan 2019 11:23:16 -0500 Message-Id: <20190128162401.58841-35-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190128162401.58841-1-sashal@kernel.org> References: <20190128162401.58841-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Will Deacon [ Upstream commit a868e8530441286342f90c1fd9c5f24de3aa2880 ] After removing an entry from a queue (e.g. reading an event in arm_smmu_evtq_thread()) it is necessary to advance the MMIO consumer pointer to free the queue slot back to the SMMU. A memory barrier is required here so that all reads targetting the queue entry have completed before the consumer pointer is updated. The implementation of queue_inc_cons() relies on a writel() to complete the previous reads, but this is incorrect because writel() is only guaranteed to complete prior writes. This patch replaces the call to writel() with an mb(); writel_relaxed() sequence, which gives us the read->write ordering which we require. Cc: Robin Murphy Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- drivers/iommu/arm-smmu-v3.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index fc6eb752ab35..eb9937225d64 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -683,7 +683,13 @@ static void queue_inc_cons(struct arm_smmu_queue *q) u32 cons = (Q_WRP(q, q->cons) | Q_IDX(q, q->cons)) + 1; q->cons = Q_OVF(q, q->cons) | Q_WRP(q, cons) | Q_IDX(q, cons); - writel(q->cons, q->cons_reg); + + /* + * Ensure that all CPU accesses (reads and writes) to the queue + * are complete before we update the cons pointer. + */ + mb(); + writel_relaxed(q->cons, q->cons_reg); } static int queue_sync_prod(struct arm_smmu_queue *q) -- 2.19.1