From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH for 4.6 13/13] xen/iommu: smmu: Add Xen specific code to be able to use the driver Date: Thu, 19 Feb 2015 10:34:54 +0000 Message-ID: <54E5BC4E.8000005@citrix.com> References: <1418760534-18163-1-git-send-email-julien.grall@linaro.org> <1418760534-18163-14-git-send-email-julien.grall@linaro.org> <54E3E49D.7000109@caviumnetworks.com> <54E47BE2.5030908@linaro.org>, <54E47D60.7010608@linaro.org> <1424280633785.32004@caviumnetworks.com> <54E4D85C.6090600@linaro.org> <54E550B2.1090605@caviumnetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta4.messagelabs.com ([85.158.143.247]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YOORl-0004Fa-DZ for xen-devel@lists.xenproject.org; Thu, 19 Feb 2015 10:35:05 +0000 In-Reply-To: <54E550B2.1090605@caviumnetworks.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Manish , Julien Grall , "Jaggi, Manish" , "xen-devel@lists.xenproject.org" Cc: "tim@xen.org" , "stefano.stabellini@citrix.com" , "ian.campbell@citrix.com" List-Id: xen-devel@lists.xenproject.org On 19/02/15 02:55, Manish wrote: > > On 18/02/15 11:52 pm, Julien Grall wrote: >> >> >> On 18/02/2015 17:30, Jaggi, Manish wrote: >>> [manish] There are general comments on the data structures >>> (a) I don't see a use case where for same domain (VM) there would be >>> different context banks , so linked list may not be required. >> >> I guess you mean the list in arm_smmu_xen_domain? All the devices >> pass-through to a domain may not be protected by the same SMMU. >> Therefore the context banks are different. > you are right. For each smmu the context bank instance for a xen > domain is duplicated with just a change in context bank id. I was > thinking can it be minimized. >> >> Also, for now a context is allocated per-device. It should be rework >> to share the context between multiple device protected by the same >> SMMU and pass-through to the same domain. > Yes, this is exactly I an doing at my end. >> >>> (b) Also iommu group may not be relevant for the same reason. >>> I am curious to find the use cases. >> >> The iommu_group is used to store the configuration of the device >> protected by an SMMU (i.e the stream ids associated to this domain). >> >> I'm a bit surprised that you think they are not useful... > How do we create an iommu_group in xen ? Xen currently has no concept of iommu groups like KVM has, and relies on the host administrator to know exactly what is and is not safe/possible to achieve. Xen really should gain the same concept, but this is a substantial quantity of work. ~Andrew