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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 854C3C001DE for ; Mon, 7 Aug 2023 20:14:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230078AbjHGUOj (ORCPT ); Mon, 7 Aug 2023 16:14:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229696AbjHGUOh (ORCPT ); Mon, 7 Aug 2023 16:14:37 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 68D1510CF; Mon, 7 Aug 2023 13:14:35 -0700 (PDT) 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 DE9021FB; Mon, 7 Aug 2023 13:15:17 -0700 (PDT) Received: from [192.168.1.102] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 702233F6C4; Mon, 7 Aug 2023 13:14:32 -0700 (PDT) Message-ID: <919ab857-30cf-00a5-1a40-fb180678792e@arm.com> Date: Mon, 7 Aug 2023 21:14:24 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v3 5.15 4/6] iommu/arm-smmu-v3: Document MMU-700 erratum 2812531 Content-Language: en-GB To: Easwar Hariharan , stable@vger.kernel.org Cc: easwar.hariharan@microsoft.com, Nicolin Chen , Will Deacon , Catalin Marinas , Jonathan Corbet , Joerg Roedel , Sasha Levin , Yicong Yang , Tomas Krcka , "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" , "open list:DOCUMENTATION" , open list , "open list:IOMMU DRIVERS" , "open list:IOMMU DRIVERS" References: <20230802170227.1590187-1-eahariha@linux.microsoft.com> <20230802170227.1590187-5-eahariha@linux.microsoft.com> From: Robin Murphy In-Reply-To: <20230802170227.1590187-5-eahariha@linux.microsoft.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-08-02 18:02, Easwar Hariharan wrote: > From: Robin Murphy > > commit 309a15cb16bb075da1c99d46fb457db6a1a2669e upstream > > To work around MMU-700 erratum 2812531 we need to ensure that certain > sequences of commands cannot be issued without an intervening sync. In > practice this falls out of our current command-batching machinery > anyway - each batch only contains a single type of invalidation command, > and ends with a sync. The only exception is when a batch is sufficiently > large to need issuing across multiple command queue slots, wherein the > earlier slots will not contain a sync and thus may in theory interleave > with another batch being issued in parallel to create an affected > sequence across the slot boundary. > > Since MMU-700 supports range invalidate commands and thus we will prefer > to use them (which also happens to avoid conditions for other errata), > I'm not entirely sure it's even possible for a single high-level > invalidate call to generate a batch of more than 63 commands, Out of interest, have you observed a case where this actually happens? > but for > the sake of robustness and documentation, wire up an option to enforce > that a sync is always inserted for every slot issued. > > The other aspect is that the relative order of DVM commands cannot be > controlled, so DVM cannot be used. Again that is already the status quo, > but since we have at least defined ARM_SMMU_FEAT_BTM, we can explicitly > disable it for documentation purposes even if it's not wired up anywhere > yet. Note that there seems to be a slight issue with this patch that I missed, under discussion here: https://lore.kernel.org/linux-iommu/27c895b8-1fb0-be88-8bc3-878d754684c8@huawei.com/T/#t Thanks, Robin. > Signed-off-by: Robin Murphy > Reviewed-by: Nicolin Chen > Link: https://lore.kernel.org/r/330221cdfd0003cd51b6c04e7ff3566741ad8374.1683731256.git.robin.murphy@arm.com > Signed-off-by: Will Deacon > Signed-off-by: Easwar Hariharan > --- > Documentation/arm64/silicon-errata.rst | 2 ++ > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 12 ++++++++++++ > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 + > 3 files changed, 15 insertions(+) > > diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst > index 55e1e074dec1..322df8abbc0e 100644 > --- a/Documentation/arm64/silicon-errata.rst > +++ b/Documentation/arm64/silicon-errata.rst > @@ -124,6 +124,8 @@ stable kernels. > +----------------+-----------------+-----------------+-----------------------------+ > | ARM | MMU-600 | #1076982 | N/A | > +----------------+-----------------+-----------------+-----------------------------+ > +| ARM | MMU-700 | #2812531 | N/A | > ++----------------+-----------------+-----------------+-----------------------------+ > +----------------+-----------------+-----------------+-----------------------------+ > | Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_845719 | > +----------------+-----------------+-----------------+-----------------------------+ > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > index 782d040a829c..6a551a48d271 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > @@ -897,6 +897,12 @@ static void arm_smmu_cmdq_batch_add(struct arm_smmu_device *smmu, > struct arm_smmu_cmdq_batch *cmds, > struct arm_smmu_cmdq_ent *cmd) > { > + if (cmds->num == CMDQ_BATCH_ENTRIES - 1 && > + (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC)) { > + arm_smmu_cmdq_issue_cmdlist(smmu, cmds->cmds, cmds->num, true); > + cmds->num = 0; > + } > + > if (cmds->num == CMDQ_BATCH_ENTRIES) { > arm_smmu_cmdq_issue_cmdlist(smmu, cmds->cmds, cmds->num, false); > cmds->num = 0; > @@ -3461,6 +3467,7 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass) > > #define IIDR_IMPLEMENTER_ARM 0x43b > #define IIDR_PRODUCTID_ARM_MMU_600 0x483 > +#define IIDR_PRODUCTID_ARM_MMU_700 0x487 > > static void arm_smmu_device_iidr_probe(struct arm_smmu_device *smmu) > { > @@ -3481,6 +3488,11 @@ static void arm_smmu_device_iidr_probe(struct arm_smmu_device *smmu) > if (variant == 0 && revision <= 2) > smmu->features &= ~ARM_SMMU_FEAT_SEV; > break; > + case IIDR_PRODUCTID_ARM_MMU_700: > + /* Arm erratum 2812531 */ > + smmu->features &= ~ARM_SMMU_FEAT_BTM; > + smmu->options |= ARM_SMMU_OPT_CMDQ_FORCE_SYNC; > + break; > } > break; > } > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > index 5964e02c4e57..abaecdf8d5d2 100644 > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h > @@ -651,6 +651,7 @@ struct arm_smmu_device { > #define ARM_SMMU_OPT_SKIP_PREFETCH (1 << 0) > #define ARM_SMMU_OPT_PAGE0_REGS_ONLY (1 << 1) > #define ARM_SMMU_OPT_MSIPOLL (1 << 2) > +#define ARM_SMMU_OPT_CMDQ_FORCE_SYNC (1 << 3) > u32 options; > > struct arm_smmu_cmdq cmdq;