Re: [Qemu-devel] [PATCH v2 0/3] Migration-safe ACPI table sizing algorithm

[Paolo Bonzini]

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?

Paolo