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[Qemu-devel] [PATCH for-4.0 v4 0/4] allow to load initrd below 4G for re

From: Li Zhijian
Subject: [Qemu-devel] [PATCH for-4.0 v4 0/4] allow to load initrd below 4G for recent kernel
Date: Thu, 6 Dec 2018 10:32:09 +0800

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/x86/head.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 bootload an optional
and safe address to load initrd.

Current QEMU/BIOS always loads initrd below below_4g_mem_size which always
less than 4G, so here limiting initrd_max to 4G - 1 simply is enough if
this bit is set.

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

  - 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
 - rebase code basing on http://patchwork.ozlabs.org/cover/1005990 and
 - 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.

Li Zhijian (4):
  unify len and addr type for memory/address APIs
  refactor 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                                 | 18 ++++++-----
 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, 92 insertions(+), 54 deletions(-)
 create mode 100644 include/standard-headers/asm-x86/bootparam.h


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