On Wed, Aug 20, 2014 at 11:27:41AM +0100, Stefan Hajnoczi wrote: > The QEMU -initrd option loads the initrd at the top of RAM. There is > a 64 KB safety region for ACPI tables in hw/i386/pc.c:load_linux(): > > initrd_max = max_ram_size-ACPI_DATA_SIZE-1; > > QEMU's bios-256k.bin SeaBIOS build reserves 128 KB at the top of > memory so the 64 KB ACPI data size has become too small. > > The guest Linux kernel rejects the initrd: > BIOS-provided physical RAM map: > BIOS-e820: 0000000000010000 - 000000000009fc00 (usable) > BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) > BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved) > BIOS-e820: 0000000000100000 - 000000003ffe0000 (usable) > BIOS-e820: 000000003ffe0000 - 0000000040000000 (reserved) > BIOS-e820: 00000000feffc000 - 00000000ff000000 (reserved) > BIOS-e820: 00000000fffc0000 - 0000000100000000 (reserved) > ... > initrd extends beyond end of memory (0x3ffef79f > 0x3ffe0000) > disabling initrd > > It is easy enough to "fix" the problem by bumping ACPI_DATA_SIZE up to > 0x20000 in QEMU. Perhaps this should only be done for bios-256k.bin > guests and not bios-128k.bin guests (QEMU 1.7 and older machine > types). > > Perhaps QEMU -> SeaBIOS -> linuxboot.bin can be simplified so QEMU > doesn't have to guess what e820 region SeaBIOS will reserve. > linuxboot.bin would probably be the place to do it unless SeaBIOS has > Linux loading functionality that could be reused. > > Any ideas? > > Stefan
I just sent a patch [PATCH] pc: reserve more memory for ACPI for new machine types to do exactly that: double the acpi memory for 2.1 and up. Would appreciate testing. -- MST