[Qemu-devel] [PATCH v5 0/4] allow to load initrd below 4G for recent kernel

[Li Zhijian]

Long long ago, linux kernel has supported up to 4G initrd, but it's header
still hard code to allow loading initrd below 2G only.
 cutting from arch/boot/x86/header.S:
 # (Header version 0x0203 or later) the highest safe address for the contents
 # of an initrd. The current kernel allows up to 4 GB, but leave it at 2 GB to
 # avoid possible bootloader bugs.

In order to support more than 2G initrd, qemu must allow loading initrd
above 2G address. Luckly, recent kernel introduced a new field to linux header
named xloadflags:XLF_CAN_BE_LOADED_ABOVE_4G which tells bootloader an optional
and safe address to load initrd.

It's believed that if XLF_CAN_BE_LOADED_ABOVE_4G is set, initrd can
be loaded into any address.

Default roms(Seabios + optionrom(linuxboot_dma)) works as expected with this
patchset.

I stole some comments from yours, fell free to let me know if you don't like 
this.

changes:
V5: add a few reviewed-tag and update 4/4 changelog and comments
V4:
  - add Reviwed-by tag to 1/4 and 2/4
  - use scripts/update-linux-headers.sh to import bootparam.h
  - minor fix at commit log
V3:
 - rebase code basing on http://patchwork.ozlabs.org/cover/1005990 and
   https://patchew.org/QEMU/address@hidden
 - add new patch 3/4 to import header bootparam.h (Michael S. Tsirkin)

V2: add 2 patches(3/5, 4/5) to fix potential loading issue.


CC: Paolo Bonzini <address@hidden>
CC: Richard Henderson <address@hidden>
CC: Eduardo Habkost <address@hidden>
CC: "Michael S. Tsirkin" <address@hidden>
CC: Marcel Apfelbaum <address@hidden>
CC: Stefano Garzarella <address@hidden>
CC: Peter Crosthwaite <address@hidden>
CC: Peter Maydell <address@hidden>

Li Zhijian (4):
  unify len and addr type for memory/address APIs
  hw/core/loader.c: Read as long as possible in load_image_size()
  i386: import & use bootparam.h
  i386: allow to load initrd below 4G for recent linux

 exec.c                                       | 47 ++++++++++++++--------------
 hw/core/loader.c                             | 11 +++----
 hw/i386/pc.c                                 | 32 ++++++++++++++-----
 include/exec/cpu-all.h                       |  2 +-
 include/exec/cpu-common.h                    |  8 ++---
 include/exec/memory.h                        | 22 ++++++-------
 include/standard-headers/asm-x86/bootparam.h | 34 ++++++++++++++++++++
 scripts/update-linux-headers.sh              |  4 +++
 8 files changed, 106 insertions(+), 54 deletions(-)
 create mode 100644 include/standard-headers/asm-x86/bootparam.h

-- 
2.7.4