From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [RFC 12/19] xen/passthrough: iommu_deassign_device_dt: By default reassign device to nobody Date: Thu, 03 Jul 2014 14:01:13 +0100 Message-ID: <53B55419.9000000@linaro.org> References: <1402935486-29136-1-git-send-email-julien.grall@linaro.org> <1402935486-29136-13-git-send-email-julien.grall@linaro.org> <1404388132.17859.27.camel@kazak.uk.xensource.com> <53B5478D.8070107@linaro.org> <1404392037.19893.6.camel@kazak.uk.xensource.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 1X2gda-0008BN-BM for xen-devel@lists.xenproject.org; Thu, 03 Jul 2014 13:01:18 +0000 Received: by mail-wg0-f50.google.com with SMTP id m15so208527wgh.9 for ; Thu, 03 Jul 2014 06:01:16 -0700 (PDT) In-Reply-To: <1404392037.19893.6.camel@kazak.uk.xensource.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: Ian Campbell Cc: xen-devel@lists.xenproject.org, stefano.stabellini@citrix.com, tim@xen.org List-Id: xen-devel@lists.xenproject.org On 07/03/2014 01:53 PM, Ian Campbell wrote: > On Thu, 2014-07-03 at 13:07 +0100, Julien Grall wrote: >>>> If Xen reassigns the device to "nobody", it may receive some global/context >>>> fault because the transaction has failed (indeed the context has been >>>> marked invalid). >>> >>> Can you describe here what happen in this case (I presume Xen tears down >>> the iommu to quiesce them somehow?) >> >> The SMMU drivers will mark the different Context Bank, S2CR, SMR as >> invalid. If the device is attempt to access the memory then, we will >> receive an interrupt in Xen. >> >> Actually it's only happen once, if the device is still enabled when the >> domain is shutdown. > > My concern was with getting a storm of such interrupts after this point. > If it only happens once and any subsequent ones are damped by some means > then great. I guess, it can happen with a buggy device trying to access memory alone. But I don't think we should care about this case. Regards, -- Julien Grall