From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shannon Zhao Subject: Re: Design doc of adding ACPI support for arm64 on Xen - version 4 Date: Thu, 27 Aug 2015 22:21:16 +0800 Message-ID: <55DF1CDC.7050106@linaro.org> References: <55D472D4.9010007@huawei.com> <55D4A95C020000780009BF99@prv-mh.provo.novell.com> <55D54C74.4060506@huawei.com> <55D5BA51020000780009C1EA@prv-mh.provo.novell.com> <55D5CE86.6090909@linaro.org> <55D5FAFC020000780009C344@prv-mh.provo.novell.com> <55D68C19.1040408@huawei.com> <55DE5BE6.8090604@citrix.com> <55DEDDF5020000780009D4B1@prv-mh.provo.novell.com> <55DF15A0.3060908@linaro.org> <55DF3714020000780009D777@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55DF3714020000780009D777@prv-mh.provo.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 , Shannon Zhao Cc: Hangaohuai , Ian Campbell , Stefano Stabellini , andrew@fubar.geek.nz, "Huangpeng(Peter)" , Julien Grall , StefanoStabellini , David Vrabel , Boris Ostrovsky , xen-devel , Parth Dixit , Christoffer Dall List-Id: xen-devel@lists.xenproject.org On 2015/8/27 22:13, Jan Beulich wrote: >>>> On 27.08.15 at 15:50, wrote: >> On 2015/8/27 15:52, Jan Beulich wrote: >>> One other aspect completely left off so far is that of proper isolation: >>> What x86 exposes to Dom0 is specifically limited to what Dom0 is >>> supposed to know. I'm getting the impression that by exposing more >>> EFI tables this is being violated just for the purpose of avoiding any >>> changes to Linux. But maybe I'm misremembering, and all the extra >>> tables exposed are actually fake ones rather than cloned host ones. >> >> Currently we create EFI system table and EFI memory descriptor table as >> Linux requires. I think the EFI memory descriptor table is necessary. >> What we didn't reach an agreement is only the EFI system table. Yes, we >> only use the Configure table of the EFI system table to get the ACPI >> root address. As you mentioned before, it could pass only the Configure >> table to Dom0, but we should change the process of parsing the DT and >> consider the backwards compatibility. > > A made up system table would (as said before) be fine with me too. > Just not a clone of the host one. > Yeah, it's a made up one. >> On the other hand, as the RUNTIME service is not supported, it could >> assign the runtime service members of EFI system table invalid values >> and let Dom0 not initialize RUNTIME service(This could be done by making >> the memory attribute not be EFI_MEMORY_RUNTIME when we create the EFI >> memory descriptor table). If the RUNTIME service is supported in the >> future, it doesn't need to change the Linux again. So it could avoid >> changing back. > > I'd strongly advise against such hackery - it will get you (and Xen) > into the bad firmware corner. EFI without runtime services doesn't > exist. And runtime services code/data not marked as such are a > firmware bug (sadly existing in reality on the x86 side). But remember > that under Xen the Dom0 kernel mustn't care about runtime services > (other than wanting to be able to invoke them through hypercalls). > Oh, I see. Thanks for your explanation. -- Shannon