From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Hudson-Doyle Subject: Re: [RFC] ARM VM System Sepcification Date: Thu, 27 Feb 2014 10:05:05 +1300 Message-ID: <87k3chh9fi.fsf@canonical.com> References: <20140226183454.GA14639@cbox> Mime-Version: 1.0 Content-Type: text/plain Cc: Peter Maydell , Ian Campbell , Michael Casadevall , "marc.zyngier\@arm.com" , Rob Herring , Stefano Stabellini , Grant Likely To: Christoffer Dall , cross-distro@lists.linaro.org, "linux-arm-kernel\@lists.infradead.org" , "kvmarm\@lists.cs.columbia.edu" , "kvm\@vger.kernel.org" , xen-devel@lists.xen.org Return-path: Received: from youngberry.canonical.com ([91.189.89.112]:53459 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751670AbaBZVFW (ORCPT ); Wed, 26 Feb 2014 16:05:22 -0500 In-Reply-To: <20140226183454.GA14639@cbox> Sender: kvm-owner@vger.kernel.org List-ID: Christoffer Dall writes: > Hardware Description > -------------------- > The Linux kernel's proper entry point always takes a pointer to an FDT, > regardless of the boot mechanism, firmware, and hardware description > method. Even on real hardware which only supports ACPI and UEFI, the kernel > entry point will still receive a pointer to a simple FDT, generated by > the Linux kernel UEFI stub, containing a pointer to the UEFI system > table. The kernel can then discover ACPI from the system tables. The > presence of ACPI vs. FDT is therefore always itself discoverable, > through the FDT. > > Therefore, the VM implementation must provide through its UEFI > implementation, either: > > a complete FDT which describes the entire VM system and will boot > mainline kernels driven by device tree alone, or > > no FDT. In this case, the VM implementation must provide ACPI, and > the OS must be able to locate the ACPI root pointer through the UEFI > system table. Maybe I'm missing something, but should this last bit say "a trivial FDT" instead of "no FDT"? If not, I don't understand the first paragraph :-) Cheers, mwh