Messages in this thread | | | Subject | Re: [PATCH v3 06/10] arm64: efi: add EFI stub | From | Jeffrey Hugo <> | Date | Wed, 8 Feb 2017 10:30:37 -0700 |
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On 2/8/2017 10:03 AM, Mark Rutland wrote: > On Wed, Feb 08, 2017 at 10:35:02AM -0600, Timur Tabi wrote: >> On 02/08/2017 10:29 AM, Ard Biesheuvel wrote: >>>>>>> + status = handle_cmdline_files(sys_table, image, cmdline_ptr, >>>>>>> + "initrd=", dram_base + SZ_512M, >>>>>>> + (unsigned long *)&initrd_addr, >>>>>>> + (unsigned long *)&initrd_size); >>>>> >>>>> So I know this patch is almost three years old, but why is there a >>>>> 512M limit on the initrd size? >>>>> >>> How do you reckon this constitutes a limit? >> >> handle_cmdline_files() calls efi_high_alloc() with that limit. I'm >> still trying to understand all the details myself, but apparently >> our firmware and initrd need to fit within the first 512MB because >> of dram_base + SZ_512M. When we change "dram_base + SZ_512M" to >> "~0", everything works. > > Just to check, how big is that initrd? > > I guess it's possible that there simply isn't sufficient contiguous free > memory in that range, even if the initrd isn't that large. Can you share > the EFI memory map dump from booting with efi=debug? > > We originally needed to restrict this to ensure that the kernel could > map the initrd (and I think the 512M restriction specifically was > inherited from the DTB mapping restriction). Since then, we have relaxed > things in the kernel, and today Documentation/arm64/booting.txt says: > > If an initrd/initramfs is passed to the kernel at boot, it must > reside entirely within a 1 GB aligned physical memory window of > up to 32 GB in size that fully covers the kernel Image as well. > > ... so I think the EFI stub should be able to take advantage of that > relaxation.
I agree. The wrinkle I can see in this is it looks like KASLR can put the kernel anywhere in RAM. How do we ensure initrd is within 32GB of the kernel on a system with 256 GB of RAM?
> > Ard? > > Thanks, > Mark. > -- > To unsubscribe from this list: send the line "unsubscribe linux-efi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
-- Jeffrey Hugo Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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