From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [RFC] ARM VM System Sepcification Date: Wed, 26 Feb 2014 13:08:21 -0800 Message-ID: <20140226210821.GD16149@cbox> References: <20140226183454.GA14639@cbox> <87k3chh9fi.fsf@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: 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, Peter Maydell , Ian Campbell , Michael Casadevall , "marc.zyngier@arm.com" , Rob Herring , Stefano Stabellini , Grant Likely To: Michael Hudson-Doyle Return-path: Received: from mail-pa0-f42.google.com ([209.85.220.42]:45599 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751159AbaBZVIR (ORCPT ); Wed, 26 Feb 2014 16:08:17 -0500 Received: by mail-pa0-f42.google.com with SMTP id kl14so1500346pab.15 for ; Wed, 26 Feb 2014 13:08:16 -0800 (PST) Content-Disposition: inline In-Reply-To: <87k3chh9fi.fsf@canonical.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Feb 27, 2014 at 10:05:05AM +1300, Michael Hudson-Doyle wrote: > 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 :-) > That trivial FDT would be generated by the EFI stub in the kernel - not provided by the VM implementation. -Christoffer From mboxrd@z Thu Jan 1 00:00:00 1970 From: christoffer.dall@linaro.org (Christoffer Dall) Date: Wed, 26 Feb 2014 13:08:21 -0800 Subject: [RFC] ARM VM System Sepcification In-Reply-To: <87k3chh9fi.fsf@canonical.com> References: <20140226183454.GA14639@cbox> <87k3chh9fi.fsf@canonical.com> Message-ID: <20140226210821.GD16149@cbox> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Feb 27, 2014 at 10:05:05AM +1300, Michael Hudson-Doyle wrote: > 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 :-) > That trivial FDT would be generated by the EFI stub in the kernel - not provided by the VM implementation. -Christoffer