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 0B29FC6FD1C for ; Tue, 14 Mar 2023 11:59:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jS62sDsIRtriAn7uZumX7uHg7apn77erWrW3cOhlSgc=; b=cdDgHr4LmwCU1D Uj+1k4BEOXJl0/3yGVvHe6LTyYe1ymSWAh01asf4z5S+fEC0SvHOzclwE6R06yQcxrXkk5OyM0Oz6 hFEE0Bt8HXZXNrTv8qRSqBFaeuZUW8NQySPk8tSu0eBGulUpyRzzmTcLB1BKrA/ewc3r3T1cLRx7o /SaDEX1rfKkDTrr1yQG0e0PAULHNIfaJGdU+/ZtvMcn5nATqBug83xicuzBqApF9HcgQl5MakMfKW mt3MenenhVXs6StE2IP67IWcZvjQFDm6+U2GWuw30jly/Y78Iv1pwNHQwIg+RIh1RIbGorkwwNFqa kyu/1i23uDyrrQkFuIxA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pc3Ia-00A37k-0j; Tue, 14 Mar 2023 11:58:36 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pc3IX-00A37J-0g for linux-arm-kernel@lists.infradead.org; Tue, 14 Mar 2023 11:58:34 +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 947054B3; Tue, 14 Mar 2023 04:59:14 -0700 (PDT) Received: from [10.57.91.139] (unknown [10.57.91.139]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E08E73F67D; Tue, 14 Mar 2023 04:58:28 -0700 (PDT) Message-ID: <13b46d42-e497-8dd7-4785-f58447128a40@arm.com> Date: Tue, 14 Mar 2023 11:58:24 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH v2] iommu/arm-smmu-qcom: Rework the logic finding the bypass quirk Content-Language: en-GB To: Manivannan Sadhasivam , Johan Hovold Cc: will@kernel.org, joro@8bytes.org, andersson@kernel.org, johan+linaro@kernel.org, steev@kali.org, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org References: <20230314105905.137241-1-manivannan.sadhasivam@linaro.org> <20230314112620.GB137001@thinkpad> From: Robin Murphy In-Reply-To: <20230314112620.GB137001@thinkpad> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230314_045833_341788_10F94AA7 X-CRM114-Status: GOOD ( 21.55 ) 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: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2023-03-14 11:26, Manivannan Sadhasivam wrote: > On Tue, Mar 14, 2023 at 12:17:38PM +0100, Johan Hovold wrote: >> On Tue, Mar 14, 2023 at 04:29:05PM +0530, Manivannan Sadhasivam wrote: >>> The logic used to find the quirky firmware that intercepts the writes to >>> S2CR register to replace bypass type streams with a fault, and ignore the >>> fault type, is not working with the firmware on newer SoCs like SC8280XP. >>> >>> The current logic uses the last stream mapping group (num_mapping_groups >>> - 1) as an index for finding quirky firmware. But on SC8280XP, NUSMRG >>> reports a value of 162 (possibly emulated by the hypervisor) and logic is >>> not working for stream mapping groups > 128. (Note that the ARM SMMU >>> architecture specification defines NUMSMRG in the range of 0-127). >>> >>> So the current logic that checks the (162-1)th S2CR entry fails to detect >>> the quirky firmware on these devices and SMMU triggers invalid context >>> fault for bypass streams. >>> >>> To fix this issue, rework the logic to find the first non-valid (free) >>> stream mapping register group (SMR) within 128 groups and use that index >>> to access S2CR for detecting the bypass quirk. If no free groups are >>> available, then just skip the quirk detection. >>> >>> While at it, let's move the quirk detection logic to a separate function >>> and change the local variable name from last_s2cr to free_s2cr. >>> >>> Reviewed-by: Bjorn Andersson >>> Signed-off-by: Manivannan Sadhasivam >>> --- >>> >>> Changes in v2: >>> >>> * Limited the check to 128 groups as per ARM SMMU spec's NUMSMRG range >>> * Moved the quirk handling to its own function >>> * Collected review tag from Bjorn >>> >>> drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 48 ++++++++++++++++++---- >>> 1 file changed, 40 insertions(+), 8 deletions(-) >>> >>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c >>> index d1b296b95c86..48362d7ef451 100644 >>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c >>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c >>> @@ -266,25 +266,49 @@ static int qcom_smmu_init_context(struct arm_smmu_domain *smmu_domain, >>> return 0; >>> } >>> >>> -static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu) >>> +static void qcom_smmu_bypass_quirk(struct arm_smmu_device *smmu) >>> { >>> - unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1); >>> struct qcom_smmu *qsmmu = to_qcom_smmu(smmu); >>> - u32 reg; >>> - u32 smr; >>> + u32 free_s2cr; >>> + u32 reg, smr; >>> int i; >>> >>> + /* >>> + * Find the first non-valid (free) stream mapping register group and >>> + * use that index to access S2CR for detecting the bypass quirk. >>> + * >>> + * Note that only the first 128 stream mapping groups are considered for >>> + * the check. This is because the ARM SMMU architecture specification >>> + * defines NUMSMRG (Number of Stream Mapping Register Groups) in the >>> + * range of 0-127, but some Qcom platforms emulate more stream mapping >>> + * groups with the help of hypervisor. And those groups don't exhibit >>> + * the quirky behavior. >>> + */ >>> + for (i = 0; i < 128; i++) { >> >> This may now access registers beyond smmu->num_mapping_groups. Should >> you not use the minimum of these two values here (and below)? >> > > Doh! yeah, you're right. Will fix it in v3. FWIW I'd say it's probably best if the cfg_probe hook clamps smmu->num_mapping_groups to the architectural maximum straight away, to also prevent the main driver iterating off into the nonsensical area in arm_smmu_device_reset() or the SMR allocator itself. (Note that we don't support the weird EXSMRGS extension that appeared in a late version of the architecture, but even if we did, that still reports 128 for IDR0.NUMSMRG, and the extra extended SMRs live somewhere completely different.) Thanks, Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel