From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Kiper Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Date: Mon, 14 Sep 2015 14:19:36 +0200 Message-ID: <20150914121936.GH4530__35612.1798664846$1442233325$gmane$org@olila.local.net-space.pl> References: <20150910121514.GE29293@leverpostej> <20150910144938.GI29293@leverpostej> <20150910162302.GN29293@leverpostej> <20150911124643.GB4530@olila.local.net-space.pl> <20150911162559.GA8726@leverpostej> <20150912113655.GG4530@olila.local.net-space.pl> <20150914092518.GA10307@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20150914092518.GA10307@leverpostej> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Mark Rutland Cc: "devicetree@vger.kernel.org" , "linux-efi@vger.kernel.org" , "Ian.Campbell@citrix.com" , "linux-doc@vger.kernel.org" , Stefano Stabellini , "linux-kernel@vger.kernel.org" , "leif.lindholm@linaro.org" , "xen-devel@lists.xen.org" , "ard.biesheuvel@linaro.org" , "freebsd-arm@freebsd.org" , "matt.fleming@intel.com" , "linux-arm-kernel@lists.infradead.org" , "jbeulich@suse.com" , Shannon Zhao , "julien.grall@citrix.com" , "peter.huangpeng@huawei.com" List-Id: xen-devel@lists.xenproject.org On Mon, Sep 14, 2015 at 10:25:19AM +0100, Mark Rutland wrote: > On Sat, Sep 12, 2015 at 12:36:55PM +0100, Daniel Kiper wrote: > > On Fri, Sep 11, 2015 at 05:25:59PM +0100, Mark Rutland wrote: > > > On Fri, Sep 11, 2015 at 01:46:43PM +0100, Daniel Kiper wrote: > > > > On Thu, Sep 10, 2015 at 05:23:02PM +0100, Mark Rutland wrote: > > > > [...] > > > > > > > What's troublesome with the boot services? > > > > > > > > > > What can't be simulated? > > > > > > > > How do you want to access bare metal EFI boot services from dom0 if they > > > > were shutdown long time ago before loading dom0 image? > > > > > > I don't want to. > > > > > > I asked "What can't be simulated?" because I assumed everything > > > necessary/mandatory could be simulated without needinng access to any > > > real EFI boot services. > > > > > > As far as I can see all that's necessary is to provide a compatible > > > interface. > > > > Could you be more precise what do you need? Please enumerate. UEFI spec has > > more than 2500 pages and I do not think that we need all stuff in dom0. > > > > > > What do you need from EFI boot services in dom0? > > > > > > The ability to call ExitBootServices() and SetVirtualAddressMap() on a > > > _virtual_ address map for _virtual_ services provided by the hypervisor. > > > > I am confused. Why do you need that? Please remember, EFI is owned and > > operated by Xen hypervisor. dom0 does not have direct access to EFI. > > Let's take a step back. > > My objection here is to passing the Dom0 kernel properties as if it were > booted with direct access to a full UEFI, then later fixing that up > (when Xen is detected and we apply its hypercall EFI implementation). > > If the kernel cannot use EFI natively, why pretend to the kernel that it > can? The hypercall implementation is _not_ EFI (though it provides > access to some services). > > The two ways I can see providing Dom0 with EFI services are: > > * Have Xen create shims for any services, in which any hypercalls live, > and pass these to the kernel with a virtual system table. This keeps > the interface to the kernel the same regardless of Xen. > > * Have the kernel detect Xen EFI capability via Xen, without passing the > usual native EFI parameters. This can then be installed into the > kernel in a Xen-specific manner, and we know from the outset that > Xen-specific caveats apply. It works on x86 in that way and I suppose that it can work in that way on ARM too. So, just go and reuse existing code. That is all. Daniel