From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [v7][PATCH 03/16] xen/passthrough: extend hypercall to support rdm reservation policy Date: Fri, 10 Jul 2015 16:07:44 +0100 Message-ID: <559FDFC0.7000609@eu.citrix.com> References: <1436420047-25356-1-git-send-email-tiejun.chen@intel.com> <1436420047-25356-4-git-send-email-tiejun.chen@intel.com> <559FFA6C020000780008F998@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <559FFA6C020000780008F998@mail.emea.novell.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: Jan Beulich , Tiejun Chen Cc: Kevin Tian , Keir Fraser , Ian Campbell , Andrew Cooper , Tim Deegan , "xen-devel@lists.xen.org" , Stefano Stabellini , Suravee Suthikulpanit , Yang Zhang , Aravind Gopalakrishnan List-Id: xen-devel@lists.xenproject.org On 07/10/2015 04:01 PM, Jan Beulich wrote: >>>> On 10.07.15 at 15:26, wrote: >> I also said that if we went with anything other than STRICT that we'd >> need to check to make sure that the domain really was the hardware >> domain before proceeding, in case the assumption that pdev->domain == >> hardware_domain ever changed. (Perhaps with an ASSERT -- Jan, what do >> you think?) > > Yes, such an ASSERT() seems okay/desirable. > >> Also, passing in RELAXED in locations where the flag is completely >> ignored (such as when removing mappings) doesn't really make any >> sense. >> >> On the whole I think it would be better if you removed the RELAXED >> flag for both removals and for hardware domains. > > But what would he pass instead? Or wait - iirc I had even suggested > a way to do so by combining two arguments. Would need to go dig > that out, because I think the idea got dropped without good reason. No, I just meant to pass '0' for the flags (which would imply STRICT). I was saying two things in the above paragraph: 1. For removal, there's no point in passing in anything other than '0' for flags, since it's ignored. Passing a non-0 value implies that the flags will have some effect, which is misleading. 2. For places we know we're adding to hw domains, I think it makes most sense also to pass in '0', to imply STRICT. But if instead they insist on passing RELAXED, then please add an ASSERT(pdev->domain == hw_domain) or something of the kind to intel_iommu_add_device(). (If defaulting to STRICT, I don't think the ASSERT is necessary anymore.) -George