From patchwork Thu Aug 9 11:48:52 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 10561271 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E5877139A for ; Thu, 9 Aug 2018 11:51:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D35372AE2B for ; Thu, 9 Aug 2018 11:51:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D1AA72AF14; Thu, 9 Aug 2018 11:51:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 6EC842AF0E for ; Thu, 9 Aug 2018 11:51:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=AZJoAvl3LRHHX7fnmKj10h7Q+xDvd4Ex2F+71fPEtpw=; b=tnvTX0P6aQt5Jg JfD77e2dcA2PjyspWVJzVQCkVm+1dDChCEVII6tFBPh2ZwE0ktod4FLALMT8f5gMG+ZJx2RPX5STO nAe+4OkEP0Dk24UihN3wv5w1C302KSS5wKuQqFXpL7VBIXUUKTwxcD3zmhp8z0s4zX2IKfyQV4CbG mBMJCAM8cAa+4wvVgkwANwHH/QCeBEOJgVef28jEfJlh60STl9XSutmHF+hj8tfkiZ9E90ey0etMC h7PBOlsEUjUq+1LAO759STwAvA10848xiPWGDrbgqoZcTgpHBrNxoGAf4FFjiRmxfl0udHudyvtfG mYdD/EHRZbmz2ZzCS5Fw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1fnjT4-0004xQ-Sr; Thu, 09 Aug 2018 11:51:02 +0000 Received: from szxga05-in.huawei.com ([45.249.212.191] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fnjSs-0004jJ-Qu for linux-arm-kernel@lists.infradead.org; Thu, 09 Aug 2018 11:50:52 +0000 Received: from DGGEMS408-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id EAD3249A3C293; Thu, 9 Aug 2018 19:50:32 +0800 (CST) Received: from localhost (10.177.23.164) by DGGEMS408-HUB.china.huawei.com (10.3.19.208) with Microsoft SMTP Server id 14.3.399.0; Thu, 9 Aug 2018 19:50:27 +0800 From: Zhen Lei To: Robin Murphy , Will Deacon , Joerg Roedel , linux-arm-kernel , iommu , linux-kernel Subject: [PATCH v2 1/2] iommu/arm-smmu-v3: fix unexpected CMD_SYNC timeout Date: Thu, 9 Aug 2018 19:48:52 +0800 Message-ID: <1533815333-17320-2-git-send-email-thunder.leizhen@huawei.com> X-Mailer: git-send-email 1.9.5.msysgit.0 In-Reply-To: <1533815333-17320-1-git-send-email-thunder.leizhen@huawei.com> References: <1533815333-17320-1-git-send-email-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.177.23.164] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180809_045051_053142_9F00BC1B X-CRM114-Status: GOOD ( 12.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Hanjun Guo , LinuxArm , Libin , Zhen Lei Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP The condition "(int)(VAL - sync_idx) >= 0" to break loop in function __arm_smmu_sync_poll_msi requires that sync_idx must be increased monotonously according to the sequence of the CMDs in the cmdq. But ".msidata = atomic_inc_return_relaxed(&smmu->sync_nr)" is not protected by spinlock, so the following scenarios may appear: cpu0 cpu1 msidata=0 msidata=1 insert cmd1 insert cmd0 smmu execute cmd1 smmu execute cmd0 poll timeout, because msidata=1 is overridden by cmd0, that means VAL=0, sync_idx=1. This is not a functional problem, just make the caller wait for a long time until TIMEOUT. It's rare to happen, because any other CMD_SYNCs during the waiting period will break it. Signed-off-by: Zhen Lei --- drivers/iommu/arm-smmu-v3.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) -- 1.8.3 diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 1d64710..d17a9a7 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -566,7 +566,7 @@ struct arm_smmu_device { int gerr_irq; int combined_irq; - atomic_t sync_nr; + u32 sync_nr; unsigned long ias; /* IPA */ unsigned long oas; /* PA */ @@ -947,14 +947,13 @@ static int __arm_smmu_cmdq_issue_sync_msi(struct arm_smmu_device *smmu) struct arm_smmu_cmdq_ent ent = { .opcode = CMDQ_OP_CMD_SYNC, .sync = { - .msidata = atomic_inc_return_relaxed(&smmu->sync_nr), .msiaddr = virt_to_phys(&smmu->sync_count), }, }; - arm_smmu_cmdq_build_cmd(cmd, &ent); - spin_lock_irqsave(&smmu->cmdq.lock, flags); + ent.sync.msidata = ++smmu->sync_nr; + arm_smmu_cmdq_build_cmd(cmd, &ent); arm_smmu_cmdq_insert_cmd(smmu, cmd); spin_unlock_irqrestore(&smmu->cmdq.lock, flags); @@ -2179,7 +2178,6 @@ static int arm_smmu_init_structures(struct arm_smmu_device *smmu) { int ret; - atomic_set(&smmu->sync_nr, 0); ret = arm_smmu_init_queues(smmu); if (ret) return ret;