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=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 0DE11C433DB for ; Fri, 22 Jan 2021 12:55:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CC926230FC for ; Fri, 22 Jan 2021 12:55:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727476AbhAVMzB (ORCPT ); Fri, 22 Jan 2021 07:55:01 -0500 Received: from foss.arm.com ([217.140.110.172]:46288 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727533AbhAVMyd (ORCPT ); Fri, 22 Jan 2021 07:54:33 -0500 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 9BD7511B3; Fri, 22 Jan 2021 04:53:41 -0800 (PST) Received: from [10.57.39.58] (unknown [10.57.39.58]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2AF2D3F66E; Fri, 22 Jan 2021 04:53:18 -0800 (PST) Subject: Re: [PATCH v2 1/3] iommu/arm-smmu: Add support for driver IOMMU fault handlers To: Will Deacon , Jordan Crouse Cc: linux-arm-msm@vger.kernel.org, iommu@lists.linux-foundation.org, Greg Kroah-Hartman , Joerg Roedel , Krishna Reddy , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20201124191600.2051751-1-jcrouse@codeaurora.org> <20201124191600.2051751-2-jcrouse@codeaurora.org> <20210122124125.GA24102@willie-the-truck> From: Robin Murphy Message-ID: <8ba2f53d-abbf-af7f-07f6-48ad7f383a37@arm.com> Date: Fri, 22 Jan 2021 12:53:17 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210122124125.GA24102@willie-the-truck> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-01-22 12:41, Will Deacon wrote: > On Tue, Nov 24, 2020 at 12:15:58PM -0700, Jordan Crouse wrote: >> Call report_iommu_fault() to allow upper-level drivers to register their >> own fault handlers. >> >> Signed-off-by: Jordan Crouse >> --- >> >> drivers/iommu/arm/arm-smmu/arm-smmu.c | 16 +++++++++++++--- >> 1 file changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> index 0f28a8614da3..7fd18bbda8f5 100644 >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> @@ -427,6 +427,7 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev) >> struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); >> struct arm_smmu_device *smmu = smmu_domain->smmu; >> int idx = smmu_domain->cfg.cbndx; >> + int ret; >> >> fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR); >> if (!(fsr & ARM_SMMU_FSR_FAULT)) >> @@ -436,11 +437,20 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev) >> iova = arm_smmu_cb_readq(smmu, idx, ARM_SMMU_CB_FAR); >> cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx)); >> >> - dev_err_ratelimited(smmu->dev, >> - "Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n", >> + ret = report_iommu_fault(domain, dev, iova, >> + fsynr & ARM_SMMU_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ); >> + >> + if (ret == -ENOSYS) >> + dev_err_ratelimited(smmu->dev, >> + "Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n", >> fsr, iova, fsynr, cbfrsynra, idx); >> >> - arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr); >> + /* >> + * If the iommu fault returns an error (except -ENOSYS) then assume that >> + * they will handle resuming on their own >> + */ >> + if (!ret || ret == -ENOSYS) >> + arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr); > > Hmm, I don't grok this part. If the fault handler returned an error and > we don't clear the FSR, won't we just re-take the irq immediately? If we don't touch the FSR at all, yes. Even if we clear the fault indicator bits, the interrupt *might* remain asserted until a stalled transaction is actually resolved - that's that lovely IMP-DEF corner. Robin. > I think > it would be better to do this unconditionally, and print the "Unhandled > context fault" message for any non-zero value of ret. > > Will >