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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 7940CC433DB for ; Thu, 21 Jan 2021 18:31:41 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 233F423A40 for ; Thu, 21 Jan 2021 18:31:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 233F423A40 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.72340.130175 (Exim 4.92) (envelope-from ) id 1l2ejy-0003C7-DM; Thu, 21 Jan 2021 18:31:30 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 72340.130175; Thu, 21 Jan 2021 18:31:30 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l2ejy-0003C0-AI; Thu, 21 Jan 2021 18:31:30 +0000 Received: by outflank-mailman (input) for mailman id 72340; Thu, 21 Jan 2021 18:31:28 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l2ejw-0003Bu-OE for xen-devel@lists.xenproject.org; Thu, 21 Jan 2021 18:31:28 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l2ejt-0006Tv-3M; Thu, 21 Jan 2021 18:31:25 +0000 Received: from [54.239.6.186] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1l2ejs-00010X-MO; Thu, 21 Jan 2021 18:31:24 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=WNo6GrYvzfBt8R0wpWriNGAxDAPy3aOWTTbEM1mFXcQ=; b=h+yBaRJhUtvGs1hPuqKngzj4Gd y4vOXKvtaSsocOfXgWkw/lAXt+AKfc35adv+NX8+hhZ5E1ehyr5DR3MwIO+T0N0qgmHE95OnoX3iQ WH6NgDRSC6ddviJAPpN5CDyal+V/ZBJ0uGgy3lyajurMxtvabpuX64dbdS7OKoUcRTX4=; Subject: Re: [PATCH v5 10/10] xen/arm: smmuv3: Add support for SMMUv3 driver To: Rahul Singh , Oleksandr Cc: "xen-devel@lists.xenproject.org" , Bertrand Marquis , Andrew Cooper , George Dunlap , Ian Jackson , Jan Beulich , Stefano Stabellini , Wei Liu , Paul Durrant , Volodymyr Babchuk References: From: Julien Grall Message-ID: Date: Thu, 21 Jan 2021 18:31:22 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit On 21/01/2021 17:18, Rahul Singh wrote: > Hello Oleksandr, Hi, >> On 20 Jan 2021, at 9:33 pm, Oleksandr wrote: >> >> >> On 20.01.21 16:52, Rahul Singh wrote: >> >> Hi Rahul >> >>> Add support for ARM architected SMMUv3 implementation. It is based on >>> the Linux SMMUv3 driver. >>> >>> Driver is currently supported as Tech Preview. >>> >>> Major differences with regard to Linux driver are as follows: >>> 2. Only Stage-2 translation is supported as compared to the Linux driver >>> that supports both Stage-1 and Stage-2 translations. >>> 3. Use P2M page table instead of creating one as SMMUv3 has the >>> capability to share the page tables with the CPU. >>> 4. Tasklets are used in place of threaded IRQ's in Linux for event queue >>> and priority queue IRQ handling. >>> 5. Latest version of the Linux SMMUv3 code implements the commands queue >>> access functions based on atomic operations implemented in Linux. >>> Atomic functions used by the commands queue access functions are not >>> implemented in XEN therefore we decided to port the earlier version >>> of the code. Atomic operations are introduced to fix the bottleneck >>> of the SMMU command queue insertion operation. A new algorithm for >>> inserting commands into the queue is introduced, which is lock-free >>> on the fast-path. >>> Consequence of reverting the patch is that the command queue >>> insertion will be slow for large systems as spinlock will be used to >>> serializes accesses from all CPUs to the single queue supported by >>> the hardware. Once the proper atomic operations will be available in >>> XEN the driver can be updated. >>> 6. Spin lock is used in place of mutex when attaching a device to the >>> SMMU, as there is no blocking locks implementation available in XEN. >>> This might introduce latency in XEN. Need to investigate before >>> driver is out for tech preview. >>> 7. PCI ATS functionality is not supported, as there is no support >>> available in XEN to test the functionality. Code is not tested and >>> compiled. Code is guarded by the flag CONFIG_PCI_ATS. >>> 8. MSI interrupts are not supported as there is no support available in >>> XEN to request MSI interrupts. Code is not tested and compiled. Code >>> is guarded by the flag CONFIG_MSI. >>> >>> Signed-off-by: Rahul Singh >>> --- >>> Changes since v2: >>> - added return statement for readx_poll_timeout function. >>> - remove iommu_get_dma_cookie and iommu_put_dma_cookie. >>> - remove struct arm_smmu_xen_device as not required. >>> - move dt_property_match_string to device_tree.c file. >>> - replace arm_smmu_*_thread to arm_smmu_*_tasklet to avoid confusion. >>> - use ARM_SMMU_REG_SZ as size when map memory to XEN. >>> - remove bypass keyword to make sure when device-tree probe is failed we >>> are reporting error and not continuing to configure SMMU in bypass >>> mode. >>> - fixed minor comments. >>> Changes since v3: >>> - Fixed typo for CONFIG_MSI >>> - Added back the mutex code >>> - Rebase the patch on top of newly added WARN_ON(). >>> - Remove the direct read of register VTCR_EL2. >>> - Fixed minor comments. >>> Changes since v4: >>> - Replace the ffsll() with ffs64() function. >>> - Add code to free resources when probe failed. >> >> Thank you for addressing, patch looks ok to me, just one small remark below: >> >> >>> + >>> +static void __hwdom_init arm_smmu_iommu_hwdom_init(struct domain *d) >>> +{ >>> +} >> >> We discussed in V4 about adding some code here which all IOMMUs on Arm already have, copy it below for the convenience: >> >> >> /* Set to false options not supported on ARM. */ >> if ( iommu_hwdom_inclusive ) >> printk(XENLOG_WARNING >> "map-inclusive dom0-iommu option is not supported on ARM\n"); >> iommu_hwdom_inclusive = false; >> if ( iommu_hwdom_reserved == 1 ) >> printk(XENLOG_WARNING >> "map-reserved dom0-iommu option is not supported on ARM\n"); >> iommu_hwdom_reserved = 0; >> >> arch_iommu_hwdom_init(d); >> >> >> Also we discussed about possibility to fold the part of code (which disables unsupported options) in arch_iommu_hwdom_init() to avoid duplication as a follow-up. >> At least, I expected to see arch_iommu_hwdom_init() to be called by arm_smmu_iommu_hwdom_init() it current patch... Please note, this is *not* a request for change immediately, >> I think, driver is functional even without this code (hopefully arch_iommu_hwdom_init is empty now, etc). But, if you happen to do V6 or probably it could be done on commit ... >> > > Yes I will send the patch to move the code to arch_iommu_hwdom_init() to avoid duplication once SMMUv3 driver will be merged. > I thought anyway I have to remove the code from SMMUv1 and IPMMU I will take care of all the IOMMU driver at the same time because of that I didn’t modify the SMMUv3 driver. There are two part in the problem here: 1) Code duplication 2) The SMMUv3 not checking the command line and calling arch_iommu_hwdom_init(d) I agree that 1) can be deferred because it is a clean-up. However, I consider 2) a (latent) bug because it means that we risk unintentionally breaking the SMMUv3 driver is we need to add code in arch_iommu_hwdom_init() as part of a future bug fix for 4.15. Therefore... > Yes if there is a need for v6 I will add the arch_iommu_hwdom_init(d) in arm_smmu_iommu_hwdom_init(). ... I think calling arch_iommu_hwdom_init() should be the strict minimum. So please address it. Although, no need to resend the full series, you can only resend patch #10. Cheers, -- Julien Grall