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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 5D0FBC10F14 for ; Tue, 23 Apr 2019 13:42:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32D5B20693 for ; Tue, 23 Apr 2019 13:42:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727666AbfDWNm0 (ORCPT ); Tue, 23 Apr 2019 09:42:26 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:56478 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726659AbfDWNm0 (ORCPT ); Tue, 23 Apr 2019 09:42:26 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 73B48A78; Tue, 23 Apr 2019 06:42:25 -0700 (PDT) Received: from [10.1.196.92] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 483363F238; Tue, 23 Apr 2019 06:42:20 -0700 (PDT) Subject: Re: [PATCH 1/7] genirq/msi: Add a new field in msi_desc to store an IOMMU cookie To: Robin Murphy , Julien Grall , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org Cc: logang@deltatee.com, douliyangs@gmail.com, miquel.raynal@bootlin.com, jason@lakedaemon.net, tglx@linutronix.de, joro@8bytes.org, bigeasy@linutronix.de, linux-rt-users@vger.kernel.org References: <20190418172611.21561-1-julien.grall@arm.com> <20190418172611.21561-2-julien.grall@arm.com> <7e77331c-4adf-5bb4-0c23-4d01a6ac5ab4@arm.com> <1bcdb72f-2116-756b-b74d-a48f89870782@arm.com> <48d14d10-0484-a7dd-cd84-a933158906ff@arm.com> <468df11c-fe2a-2584-7306-185531653331@arm.com> From: Marc Zyngier Openpgp: preference=signencrypt Autocrypt: addr=marc.zyngier@arm.com; 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Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <468df11c-fe2a-2584-7306-185531653331@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 23/04/2019 14:19, Robin Murphy wrote: > On 23/04/2019 12:46, Marc Zyngier wrote: >> On 23/04/2019 11:51, Julien Grall wrote: >>> On 4/23/19 11:23 AM, Marc Zyngier wrote: >>>> Hi Julien, >>> >>> Hi Marc, >>> >>>> On 18/04/2019 18:26, Julien Grall wrote: >>>>> When an MSI doorbell is located downstream of an IOMMU, it is required >>>>> to swizzle the physical address with an appropriately-mapped IOVA for any >>>>> device attached to one of our DMA ops domain. >>>>> >>>>> At the moment, the allocation of the mapping may be done when composing >>>>> the message. However, the composing may be done in non-preemtible >>>>> context while the allocation requires to be called from preemptible >>>>> context. >>>>> >>>>> A follow-up patch will split the current logic in two functions >>>>> requiring to keep an IOMMU cookie per MSI. >>>>> >>>>> This patch introduces a new field in msi_desc to store an IOMMU cookie >>>>> when CONFIG_IOMMU_DMA is selected. >>>>> >>>>> Signed-off-by: Julien Grall >>>>> --- >>>>> include/linux/msi.h | 3 +++ >>>>> 1 file changed, 3 insertions(+) >>>>> >>>>> diff --git a/include/linux/msi.h b/include/linux/msi.h >>>>> index 7e9b81c3b50d..d7907feef1bb 100644 >>>>> --- a/include/linux/msi.h >>>>> +++ b/include/linux/msi.h >>>>> @@ -77,6 +77,9 @@ struct msi_desc { >>>>> struct device *dev; >>>>> struct msi_msg msg; >>>>> struct irq_affinity_desc *affinity; >>>>> +#ifdef CONFIG_IOMMU_DMA >>>>> + const void *iommu_cookie; >>>>> +#endif >>>>> >>>>> union { >>>>> /* PCI MSI/X specific data */ >>>>> >>>> >>>> Given that this is the only member in this structure that is dependent >>>> on a config option, you could also add a couple of accessors that would >>>> do nothing when IOMMU_DMA is not selected (and use that in the DMA code). >>> >>> I haven't seen any use of the helpers so far because the DMA code is >>> also protected by IOMMU_DMA. >>> >>> I can add the helpers in the next version if you see any use outside of >>> the DMA code. >> >> There may not be any user user yet, but I'd surely like to see the >> accessors. This isn't very different from the stub functions you add in >> patch #2. > > If you foresee this being useful in general, do you reckon it would be > worth decoupling it under its own irqchip-layer Kconfig which can then > be selected by IOMMU_DMA? I think that'd be a useful thing to do, as most architectures do not require this dynamic mapping of MSIs. Thanks, M. -- Jazz is not dead. It just smells funny...