Messages in this thread | | | Date | Fri, 16 Nov 2012 08:17:42 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 0/9] x86, boot, 64bit: Add support for loading ramdisk and bzImage high |
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On 11/16/2012 12:53 AM, Yinghai Lu wrote: > Now we have limit kdump reseved under 896M, because kexec has the limitation. > and also bzImage need to stay under 4g. > > To make kexec/kdump could use range above 4g, we need to make bzImage and > ramdisk could be loaded above 4g. > During booting bzImage will be unpacked on same postion and stay high. > > The patches add field in boot header to > 1. get info about ramdisk position info above 4g from bootloader/kexec > 2. set code64_start_offset in header for bzImage and bootloader/kexec load > could check that to decide if need to put bzImage high. > > This patches is tested with kexec tools with local changes, will send kexec > tools change to kexec list later. > > could be found at: > git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-x86-boot > > and it is on top of for-x86-mm >
Mostly a good series, but the 0x208 is a showstopper. 0x200 is awkward as an ABI (too big to just make a jump table, but potentially too small to hold all the code needed.) I have sent some other comments, too.
If 0x200 is too small, it isn't a huge problem; we can put a jump at 0x200 and continue the 32-bit code afterwards:
/* 32-bit code */
jmp 1f
.org 0x200 .code64 ENTRY(startup_64) jmp start_64_real
.code32 1: /* 32-bit code continues... */
It is annoying because it has to be placed by hand, but isn't actually a problem. The easy way to do this is probably to push verify_cpu.S into the post-entry-point area. The .code64/.code32 don't actually do anything for a simple jmp, but are added for documentation.
How is collecting comments and ACKs for for-x86-mm coming? I'd like to do another review pass today and putting it in -tip if it is in better shape. Otherwise I suspect we'll be looking at 3.9, which is OK, of course.
-hpa
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