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spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:Cc:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PK5eNtcs7uFiHIJOGy89a647sSLTwa/VSyvyZdoDS9o=; b=nibbYyHYwWpnCb2w29HZnSS81 zBHZUTzsoof9ow7ZAnGHswFQc0qenqBXk59wEIZq5rJEEf97J+Mg3C22SPWfGSxWEwuxF8cz3kaKt PaM6Cf0y09MCEFnp7g7Xh0tvsWGMeIyAmqyotKgZGY9EvlPV5xmTYHmrHh6LbgPBmopogh+hi0tqX 6jAmaVCypTcpx5ryubfeFPxT1ZIA/VmMXXacsoZx9IiaKTuDiVGOY9DZPXZVEa6vxFp7rNm0Jv0f1 jqQhvhEG3l25FQjSGEhd27Re17e2NUT7uvQ1/Cqri02mYfln9UWLR6tS0eXD6a/rSJfluK87L6OXX DOuC/wkwg==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1ljO2s-004NOQ-Ad; 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Wed, 19 May 2021 15:23:33 +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 34EF511D4; Wed, 19 May 2021 08:23:29 -0700 (PDT) Received: from [10.57.66.179] (unknown [10.57.66.179]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7E1C63F73D; Wed, 19 May 2021 08:23:27 -0700 (PDT) Subject: Re: [PATCH 3/6] vfio: remove the unused mdev iommu hook To: Joerg Roedel , Jason Gunthorpe Cc: "Tian, Kevin" , "kvm@vger.kernel.org" , Will Deacon , Kirti Wankhede , "iommu@lists.linux-foundation.org" , Alex Williamson , David Woodhouse , Christoph Hellwig , "linux-arm-kernel@lists.infradead.org" References: <20210513120058.GG1096940@ziepe.ca> <20210514121925.GI1096940@ziepe.ca> <20210514133143.GK1096940@ziepe.ca> <20210517123010.GO1096940@ziepe.ca> <20210517133500.GP1096940@ziepe.ca> From: Robin Murphy Message-ID: <131327e3-5066-7a88-5b3c-07013585eb01@arm.com> Date: Wed, 19 May 2021 16:23:21 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210519_082331_904450_20F1830B X-CRM114-Status: GOOD ( 19.12 ) 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 2021-05-17 16:35, Joerg Roedel wrote: > On Mon, May 17, 2021 at 10:35:00AM -0300, Jason Gunthorpe wrote: >> Well, I'm sorry, but there is a huge other thread talking about the >> IOASID design in great detail and why this is all needed. Jumping into >> this thread without context and basically rejecting all the >> conclusions that were reached over the last several weeks is really >> not helpful - especially since your objection is not technical. >> >> I think you should wait for Intel to put together the /dev/ioasid uAPI >> proposal and the example use cases it should address then you can give >> feedback there, with proper context. > > Yes, I think the next step is that someone who read the whole thread > writes up the conclusions and a rough /dev/ioasid API proposal, also > mentioning the use-cases it addresses. Based on that we can discuss the > implications this needs to have for IOMMU-API and code. > > From the use-cases I know the mdev concept is just fine. But if there is > a more generic one we can talk about it. Just to add another voice here, I have some colleagues working on drivers where they want to use SMMU Substream IDs for a single hardware block to operate on multiple iommu_domains managed entirely within the kernel. Using an mdev-like approach with aux domains is pretty much the ideal fit for this use-case, while all the IOASID discussion appears centred on SVA and userspace interfaces, and as such barely relevant if at all. I seem to recall a non-trivial amount of effort going into the aux domain design too, so the promise of replacing it with "a big TBD" just because vfio-mdev turned out to be awful hardly fills me with enthusiasm either :/ Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel