From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: Design doc of adding ACPI support for arm64 on Xen - version 5 Date: Wed, 2 Sep 2015 11:18:53 +0200 Message-ID: <20150902091853.GA18705@cbox> References: <55E1042C.6000308@linaro.org> <55E43E36.90108@citrix.com> <55E4428C.7020308@huawei.com> <55E449DA.6080309@citrix.com> <55E525A8.3010302@huawei.com> <55E58BC7.7090403@citrix.com> <55E59B77.2090905@huawei.com> <55E5AADB.70503@citrix.com> <55E690DC.6000303@huawei.com> <55E6C45002000078000D7CCA@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <55E6C45002000078000D7CCA@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 Cc: hangaohuai@huawei.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, shannon.zhao@linaro.org, andrew@fubar.geek.nz, peter.huangpeng@huawei.com, julien.grall@citrix.com, stefano.stabellini@citrix.com, david.vrabel@citrix.com, zhaoshenglong@huawei.com, boris.ostrovsky@oracle.com, xen-devel@lists.xen.org, parth.dixit@linaro.org, roger.pau@citrix.com List-Id: xen-devel@lists.xenproject.org Hi Jan, On Wed, Sep 02, 2015 at 02:41:36AM -0600, Jan Beulich wrote: > >>> Shannon Zhao 09/02/15 8:03 AM >>> > >There are some descriptions in Documentation/arm64/booting.txt of Linux: > > > >"The Image must be placed text_offset bytes from a 2MB aligned base > >address near the start of usable system RAM and called there. Memory > >below that base address is currently unusable by Linux, and therefore it > >is strongly recommended that this location is the start of system RAM. > >At least image_size bytes from the start of the image must be free for > >use by the kernel." > > > >From this, it says "Memory below that base address is currently unusable > >by Linux". So if we put these tables below Dom0 RAM address and even > >describe these regions as RAM, the Linux could not use them. > > May I remind you that a design should not take specific guest OS > implementation details (which even for that one OS may change over time) > as the basis for decisions? > While I agree that the guest behavior should not dictate an unfortunate design, surely factoring in the behavior of the expected guests in the design is a reasonable thing to do? Changing the boot requirements of Linux for an architecture is a really invasive change, IMHO, and should be avoided if possible. Are there other acceptable solutions for placing the EFI tables somewhere else that would work? Thanks, -Christoffer