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 5 Date: Tue, 1 Sep 2015 12:12:24 +0800 Message-ID: <55E525A8.3010302@huawei.com> References: <55E02DC5.4090202@huawei.com> <55E05A2F.1090305@citrix.com> <55E1042C.6000308@linaro.org> <55E43E36.90108@citrix.com> <55E4428C.7020308@huawei.com> <55E449DA.6080309@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55E449DA.6080309@citrix.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: Julien Grall , Shannon Zhao , xen-devel , Christoffer Dall , Ian Campbell , Stefano Stabellini , Stefano Stabellini , Jan Beulich , Parth Dixit , andrew@fubar.geek.nz, Boris Ostrovsky , David Vrabel , Roger Pau Monne Cc: Hangaohuai , "Huangpeng (Peter)" List-Id: xen-devel@lists.xenproject.org On 2015/8/31 20:34, Julien Grall wrote: > > > On 31/08/2015 13:03, Shannon Zhao wrote: >>>> Currently I use the last RAM bank(kinfo->mem.bank[nr_banks - 1]) to >>>> calculate the start address of non-RAM place. I'm not sure there >>>> will be >>>> no MMIO at that place. Do you have any good idea to find such sure and >>>> safe non-ram place? >>> >>> It's not a safe place because with the direct mapping for the RAM, DOM0 >>> RAM could live in the last bank. >> >> I put the tables after the last bank currently. > > I misread your suggestion and though you were planning to use the last > host memory bank region for the UEFI tables. > > So what you are suggesting is not safe at all, what does ensure you that > there is no MMIO right after the last DOM0 bank? The DOM0 RAM region may > lives at the edge of a host RAM bank. > Yes, you're right. >> >>> Furthermore, for the grant table >>> region, we are re-using the RAM region used by Xen (find_gnttab_region), >>> so it may clash with it too because Xen is relocated as high as >>> possible. >>> >> >> Oh, I didn't realize this. >> >>> Although, given that the grant table region will be found by Linux when >>> ACPI is used (see your section 3.), we could be able to re-use the Xen >>> region to store the new tables/structures. >>> >> >> So you mean it's fine to put the tables after last bank of Dom0 RAM? > > No, see my answer above. I'm suggesting to re-use the same trick as we > do for the grant table region. We know that this region will never be > allocated in the DOM0 address space either because of the direct mapping > or because it's very unlikely in the case of the non-direct mapping (Xen > RAM region is very high). > I tried this. Directly use the "kinfo->gnttab_start = __pa(_stext)" as the address where these tables are mapped to Dom0. But the value of gnttab_start is lower than the start of RAM, so Dom0 ingore these regions and boot failed. see early_init_dt_add_memory_arch() >> >> In addition, how does UEFI find the space to place the tables? Could we >> use the same way? > > I think that those tables are living in the RAM and region used are > marked as reserved. > So can we use the same way for Dom0? I think the Linux will reserve the regions for EFI in reserve_regions(). Therefore, Dom0 will not use these reserved regions for other use. -- Shannon