On Thu, 10 Sep 2015, Mark Rutland wrote: > Hi, > > I'm not necessarily opposed to the renaming, but I think that this is > the least important thing to standardize for this to work. > > On Thu, Sep 10, 2015 at 09:41:56AM +0100, Shannon Zhao wrote: > > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx> > > > > These EFI stub parameters are used to internal communication between EFI > > stub and Linux kernel and EFI stub creates these parameters. But for Xen > > on ARM when booting with UEFI, Xen will create a minimal DT providing > > these parameters for Dom0 and Dom0 is not only Linux kernel, but also > > other OS (such as FreeBSD) which will be used in the future. > > Currently the Linux EFI stub and kernel have a symbiotic relationship, > because they're intimately coupled and we don't have kexec (yet) on EFI > platforms to loosen that coupling. > > If an agent other than the (kernel-specific) stub is going to provide > this to the kernel, then we need more specified than just the property > names. > > That at least includes the following: > > * The state of boot services (we currently have the EFI stub call > ExitBootServices(), and I believe this is crucial to the plan for > kexec). > > * The state of the address map (we currently have the EFI stub call > SetVirtualAddressMap()). > > * The virtual address range(s) that SetVirtualAddressMap() may map > elements to (this logic is currently in the EFI stub, and this matches > the expectations of the kernel that it is tied to). > > > So here we plan to standardize the names by dropping the prefix > > "linux," and make them common to other OS. Also this will not break > > the compatibility since these parameters are used to internal > > communication between EFI stub and kernel. > > For the moment this is true, but will not be once we have kexec, so > there's a dependency (or anti-dependency) there. > > > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx> > > --- > > Look at [1] for the discussion about this in Xen ML. The purpose of this > > patch is to standardize the names to make Linux ARM kernel work on Xen > > with UEFI. Also it hopes other OS(e.g. FreeBSD), which will be used as > > Dom0 on Xen, could support this mechanism as well. > > > > [1]http://lists.xenproject.org/archives/html/xen-devel/2015-08/msg02250.html > > Per this post, it looks like to pass a DTB to the kernel Xen already > needs to know it's a Linux kernel... > > I wasn't aware that there was a common standard for arm(64) kernels > other than a PE/COFF EFI application. > > Does Xen not talk to EFI itself and/or give the kernel a virtual EFI > interface? Xen talks to EFI itself but the interface provided to dom0 is somewhat different: there are no BootServices (Xen calls ExitBootServices before running the kernel), and the RuntimeServices go via hypercalls (see drivers/xen/efi.c). -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
