On Wed, Jan 21, 2015 at 03:42:43PM +0000, Catalin Marinas wrote: > On Wed, Jan 21, 2015 at 03:29:52PM +0000, Jon Masters wrote: > > On 01/21/2015 10:23 AM, Catalin Marinas wrote: > > > I have some questions for the ACPI and EFI folk: > > > > > > 1. When booting with ACPI, are the EFI run-time services required for > > > anything? If yes, Xen may have a bigger problem > > > > Yes. At least for some things. For example, installing an Operating > > System would require that you make runtime services calls to set the > > BootOrder/BootNext variables, and so on. Further, we use the GetTime > > service and EFI based reboot to avoid having special drivers. I had > > those added to SBBR as requirements for that reason. > > So what would a kexec'ed kernel do here? Or we usually expect it to be > short lived and doesn't need reboot, nor GetTime. > > Xen is slightly more problematic but I wonder whether it could run a > (paravirtualised) UEFI. > > > > 2. Could a boot loader (either kernel doing kexec or Xen) emulate the > > > EFI system/config tables and still make them useful to the kernel but > > > without EFI_BOOT or EFI_RUNTIME_SERVICES? > > > > Yes. But again, without the other required pieces (including the > > services function pointers in the systab which are required) you'd crash > > soon after boot trying to make those calls. > > My point was whether you can still pass information like RSDP address > via EFI tables but explicitly disable runtime services so that the > kernel won't try to make such calls (and crash). > There is no specific dependency from ACPI->EFI its just the only current method defind to get the RSDP pointer. It would work just as well getting the pointer from /chosen/ if we just pick a node and document it for Xen/kexec/other usage. We were running ACPI on machine from u-boot doing exactly this for a long time. Graeme -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
