Il 02/10/2014 14:11, Michael S. Tsirkin ha scritto: > Summarizing what you say, there are two issues around ACPI tables: > - linuxboot uses FW CFG to for memory allocations, > seabios ignores that, so they might conflict. > Let's fix either linuxboot or seabios (or both!) > and forget about it.
We can fix linuxboot, it is easy. These patches do fix John's scenario, but that is not the main issue. They are not an _attempt_ to fix it, they just do so more or less by chance. Their real purpose is fixing the second issue: > - table size changes cause cross version migration issues > this is really due to the fact we are using RAM > to migrate ACPI tables. > IMHO a more robust fix would be to allow RAM size to change > during migration, or to avoid using RAM, switch to another type of > object. Allowing fw_cfg size to change during migration (does not matter if it is stored in RAM or otherwise) is a huge can of worms because the host might have loaded the size and stored it somewhere, way before migration. Extreme example: the guest could expect the size to remain the same at boot time and S3 resume time. So I think the fw_cfg size is guest ABI and cannot change across migration anyway. > So both issues have other solutions, and I think it's a good > idea to focus on them for now. > Also, I really would like to avoid having ACPI sizing-related > issues for this release. The memory of 2.1.X pain is too fresh :) Yeah, I understand that. But I think the scary part of this series is actually the first two patches, rather than the ACPI sizing algorithm. Paolo > I'm not NACKing this patchset, but let's > make some progress on the bigger issues listed above, then come > back and address sizing as appropriate. > > Thanks! > >> >> Paolo Bonzini (6): >> pc: initialize fw_cfg earlier >> pc: load the kernel after ACPI tables are built >> pc: redo sizing of reserved high memory area for -kernel/-initrd >> 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 | 23 +++++++++------- >> hw/i386/pc.c | 72 >> +++++++++++++++++---------------------------------- >> hw/i386/pc_piix.c | 32 ++++++++++++++-------- >> hw/i386/pc_q35.c | 7 ++-- >> include/hw/i386/pc.h | 4 ++ >> 5 files changed, 66 insertions(+), 72 deletions(-)
