On Tue, Nov 11, 2014 at 03:29:33PM +0000, Mark Rutland wrote:
Hi,
On Thu, Nov 06, 2014 at 01:33:20PM +0000, Alexander Spyridakis wrote:
On 6 November 2014 14:44, Peter Maydell peter.maydell@linaro.org wrote:
We need ACPI guest support in QEMU for AArch64 over here, with all features (including the ability to run ACPI code and add specific tables), for ACPI-based guests.
The plan for providing ACPI to guests is that we run a UEFI BIOS blob which is what is responsible for providing ACPI and UEFI runtime services to guests which need them. (The UEFI blob finds out about its hardware by looking at a device tree that QEMU passes it, but that's a detail between QEMU and its bios blob). This pretty much looks like what x86 QEMU used to do with ACPI for a very long time, so we know it's a feasible approach.
Hi Peter,
The rational in the proposed approach is meant for cases where the user does not want to rely on external firmware layers. While UEFI could do what you are describing, the point is to avoid this not so trivial overhead in the booting process. Especially in the case of thin guests, where another software dependency is undesired.
I'm not sure how you plan to use ACPI without UEFI, as there are several pieces of information which ACPI misses, such as the memory map, which must be discovered from UEFI. How do you intend to discover the memory map without UEFI?
Additionally, with Linux and other generic OSs, the expectation is that the ACPI tables are discovered via the UEFI system table. How do you intend to discover the ACPI tables? Or other system information?
FWIW, Xen needs to pass the RDSP pointer along with a tiny DT containing the command line and memory information to Dom0 as well. We are currently suggesting adding an RDSP property to the chosen node in the tiny DT, but a command-line arguement like kexec proposed could be another option I guess, albeit not a very pretty one.
But, what I hear from Huawei is that they don't want any DT and don't want any UEFI, so not sure how they plan on accomplishing that.
-Christoffer