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 patchset. changes: V3: - rebase code basing on http://patchwork.ozlabs.org/cover/1005990 and https://patchew.org/QEMU/20181122133507.30950-1-peter.mayd...@linaro.org - 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 bootparam.h i386: allow to load initrd below 4G for recent linux exec.c | 47 +++++++++++++++++++++++------------------------ hw/core/loader.c | 11 +++++------ hw/i386/pc.c | 25 ++++++++++--------------- include/exec/cpu-all.h | 2 +- include/exec/cpu-common.h | 8 ++++---- include/exec/memory.h | 22 +++++++++++----------- 6 files changed, 54 insertions(+), 61 deletions(-) -- 2.7.4
