From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters Date: Thu, 10 Sep 2015 17:23:02 +0100 Message-ID: <20150910162302.GN29293@leverpostej> References: <1441874516-11364-1-git-send-email-zhaoshenglong@huawei.com> <20150910095208.GA29293@leverpostej> <20150910112418.GC29293@leverpostej> <20150910121514.GE29293@leverpostej> <20150910144938.GI29293@leverpostej> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-doc-owner@vger.kernel.org To: Stefano Stabellini Cc: Shannon Zhao , "linux-arm-kernel@lists.infradead.org" , "devicetree@vger.kernel.org" , "linux-efi@vger.kernel.org" , "Ian.Campbell@citrix.com" , "linux-doc@vger.kernel.org" , "ard.biesheuvel@linaro.org" , "linux-kernel@vger.kernel.org" , "leif.lindholm@linaro.org" , "xen-devel@lists.xen.org" , "julien.grall@citrix.com" , "freebsd-arm@freebsd.org" , "matt.fleming@intel.com" , "christoffer.dall@linaro.org" , "jbeulich@suse.com" , "peter.huangpeng@huawei.com" List-Id: devicetree@vger.kernel.org > > C) When you could go: > > > > DT -> Discover Xen -> Xen-specific stuff -> Xen-specific EFI/ACPI discovery > > I take you mean discovering Xen with the usual Xen hypervisor node on > device tree. I think that C) is a good option actually. I like it. Not > sure why we didn't think about this earlier. Is there anything EFI or > ACPI which is needed before Xen support is discovered by > arch/arm64/kernel/setup.c:setup_arch -> xen_early_init()? Currently lots (including the memory map). With the stuff to support SPCR, the ACPI discovery would be moved before xen_early_init(). > If not, we could just go for this. A lot of complexity would go away. I suspect this would still be fairly complex, but would at least prevent the Xen-specific EFI handling from adversely affecting the native case. > > D) If you want to be generic: > > EFI -> EFI application -> EFI tables -> ACPI tables -> Xen-specific stuff > > \------------------------------------------/ > > (virtualize these, provide shims to Dom0, but handle > > everything in Xen itself) > > I think that this is good in theory but could turn out to be a lot of > work in practice. We could probably virtualize the RuntimeServices but > the BootServices are troublesome. What's troublesome with the boot services? What can't be simulated? > > E) Partially-generic option: > > EFI -> EFI application -> Xen detected by registered GUID -> Xen-specific EFI bootloader stuff -> OS in Xen-specific configuration > > > > > > > > > In any case this should be separate from the shim ABI discussion. > > > > > > > > I disagree; I think this is very much relevant to the ABI discussion. > > > > That's not to say that I insist on a particular approach, but I think > > > > that they need to be considered together. > > > > > > Let's suppose Xen didn't expose any RuntimeServices at all, would that > > > make it easier to discuss about the EFI stub parameters? > > > > It would simply the protocol specific to Xen, certainly. > > > > > In the grant scheme of things, they are not that important, as Ian > > > wrote what is important is how to pass the RSDP. > > > > Unfortunately we're still going to have to care about this eventually, > > even if for something like kexec. So we still need to spec out the state > > of things if this is going to be truly generic. > > Fair enough. My position is that if we restrict this to RuntimeServices, > it might be possible, but I still prefer C). Regardless of what we do we still need a well-defined state here, which brings us back to the initial problem eventually. Thanks, Mark.