On Fri, 13 Sep 2013 12:22:13 +0100, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote: > On Fri, 2013-09-13 at 11:13 +0100, Grant Likely wrote: > > On Wed, Sep 4, 2013 at 5:41 PM, Rob Herring <robherring2@xxxxxxxxx> wrote: > > >> For u-boot Andre has proposed some syntactic sugar over the "fdt" > > >> command to make boot.scr more trivial to use. We would of course need to > > >> implement support for using it in the relevant distro tools (but they > > >> tend to be very distro/machine specific already, e.g. Debian's > > >> flash-kernel) > > > > > > And being machine specific is a PITA. flash-kernel is certainly not > > > something we want to expand on. There is not much love for boot.scr > > > either. There is work to address what are not really machine > > > differences, but largely vendor u-boot differences: > > > > > > http://www.mail-archive.com/u-boot@xxxxxxxxxxxxx/msg119025.html > > > > > > One option for u-boot which already supports syslinux style menu files > > > is to adopt the syslinux multiboot parsing support: > > > > > > http://www.syslinux.org/wiki/index.php/Doc/mboot > > > > Even building it into U-Boot is problematic because it leaves older > > machines out in the cold. Leif's port of Grub to U-Boot is far more > > interesting since the distro can now be in control of the code that > > loads the images and jumps into the kernel/hypervisor. > > AIUI this is not being developed any further? Last I checked the patches have been posted for merging, but it is stalled on the Grub maintainer. I believe he wanted to fix a bug on the raspberry pi before merging. Leif would know more. LEG isn't actively working on it anymore since UEFI is the priority, but I wouldn't call it abandoned. > > > We need to back-up and consider what this looks like in the end for > > > all the pieces and get input from folks on grub, UEFI, and armv8. The > > > UEFI answer may be this is a grub problem. For armv8, this proposal > > > does match up well as the kernel boot interface for v8 is DT. Despite > > > some claims, ACPI will not completely replace DT because of this. > > > > Yes, for UEFI it is absolutely an OS loader problem. UEFI provides an > > API and runtime environment. Grub is in general moving towards a boot > > menu system and a tool for loading images. Actual booting however > > should be done by a separate OS loader application. For Linux, this > > will be an in-kernel UEFI Stub. > > I'm not sure I follow your distinction between loading the images and > "actual booting". If grub loads the images and Linux stub does the > actual booting how does this stub locate the images which grub loaded? (Note: this isn't implemented yet, but is in progress) The DTB will need to be passed via the UEFI system table. Initrd is passed by modifying the dtb with linux,initrd-* properties in the device tree. In the Xen case, I think the original proposal is conceptually sound. I'll quibble about a couple of the details, but I'll address those with a reply to the original proposal. It makes perfect sense to use the same mechanism as the initrd properties to tell the kernel about additional blobs. > Or are you saying the stub should load the initramfs itself? How does it > know where to find it? Having the kernel in one config file (grub's) and > the initramfs in another (the Linux UEFI stub's) seems likely to result > in things getting out of sync. Having Linux's stub parse the grub CFG is > even less likely to work well IMHO. The stub has the ability to load both the dtb and initrd itself by adding "dtb=" and "initrd=" arguments, but it is currently limited to loading images from the same filesystem that the kernel was loaded from. GRUB (or gummiboot/refind/etc) is potentially more flexible. > > For Xen I would recommend taking the > > Linux EFI stub code and doing the same thing. There really isn't a > > need for a multiboot spec when you can rely on a runtime execution > > environment for setting things up exactly as you want them. > > If this works for Linux on EFI then I see no reason it could work for > Xen on EFI (assuming my questions above are just a result of my > misunderstanding something) > > But... Xen also wants to support non-server and therefore non-EFI > systems i.e. u-boot. We also want to support v7 where EFI is not a given > even for servers AIUI. I was only responding to the UEFI question, but that aside, I don't see a problem with adding properties to the DT for telling Xen where they are. > Given that I think it is a given that Xen will have some sort of > protocol along these lines, for use in these environments even if it > does the EFI stub thing on EFI systems. The question is shall we make it > more general and useful to others or just go our own way? I'd prefer to > do the former. Yes, make it general. GRUB and the EFI stub will use it. g. -- 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
