On Thu, Nov 20, 2014 at 07:05:05AM +0100, Paolo Bonzini wrote: > > > On 11/11/2014 18:13, Paolo Bonzini wrote: > > > > > > On 06/10/2014 16:56, Paolo Bonzini wrote: > >> In the emergency last-minute patches of QEMU 2.1 we did two things: > >> > >> - fixed migration problems from 1.7 or 2.0 to 2.1 due to changes in > >> ACPI table sizes > >> > >> - ensured that future versions will not break migration compatibility > >> with 2.2 for reasonable configurations (with ACPI tables smaller > >> than a hundred kilobytes, roughly) > >> > >> However, this came at the cost of wasting 128 KB unconditionally on > >> even the smaller configuration, and we didn't provide a mechanism to > >> ensure compatibility with larger configurations. > >> > >> This series provides this mechanism. As mentioned early, the design > >> is to consider the SSDT immutable and versioned (together with other > >> non-AML tables such as HPET, TPMA and MADT, SRAT, MCFG, DMAR). > >> The DSDT instead can change more or less arbitrarily. To do this, > >> we add padding after the DSDT to allow for future growth (patch 1). > >> > >> Once we do this, the size of the ACPI table fw_cfg "file" is constant > >> given a machine type and a command-line, so we do not need anymore the > >> larger 128KB padding (patch 2). > >> > >> Patch 3 is just cleanups. > >> > >> Paolo > >> > >> v1->v2: drop linuxboot changes, instead modify the option ROM > >> in a separate patch > >> > >> Paolo Bonzini (3): > >> pc: introduce new ACPI table sizing algorithm > >> pc: go back to smaller ACPI tables > >> pc: clean up pre-2.1 compatibility code > >> > >> hw/i386/acpi-build.c | 20 +++++++++++--------- > >> hw/i386/pc_piix.c | 20 +++++++++++++++++++- > >> hw/i386/pc_q35.c | 6 ++++-- > >> include/hw/i386/pc.h | 2 ++ > >> 4 files changed, 36 insertions(+), 12 deletions(-) > >> > > > > Ping? > > Ping?? > > Paolo
I thought we agreed we'll consider alternate approaches after 2.2? I would prefer not to have yet another mode to support if we can help it. -- MST