Re: [Qemu-devel] [PATCH 0/4] acpi: move common parts of the SSDT to the DSDT (and preview of things to come)

[Paolo Bonzini <pbonzini@redhat.com>]

On 24/12/2014 14:12, Paolo Bonzini wrote:
> Right now, the SSDT/DSDT is split in three parts:
> 
> - code that doesn't need patching goes in the DSDT.  Furthermore,
>   code in this category that is shared between PIIX4 and Q35 is
>   handled via #include.  There was one exception, the SMC._STA
>   method is patched and is in the DSDT.
> 
> - shared code that needs patching goes in the SSDT
> 
> - template-based code that comes from command line arguments
>   goes in the SSDT as well
> 
> This series changes things to:
> 
> - code that is chipset-specific goes in the DSDT first.
>   Right now none of this needs patching
> 
> - code that is not chipset-specific, some of which needs
>   patching, goes in the DSDT second
> 
> - template-based code that comes from command line arguments
>   goes in the SSDT
> 
> Patch 1 moves ssdt-misc ("common code that needs patching")
> to the DSDT.  Patches 2-4 stop using the C preprocessor
> in the DSDTs.
> 
> Patches 5-7 show why this could be useful.  They add padding
> in fw_cfg after the DSDT, and in exchange stop padding the ACPI
> tables to 128K.  This fixes migration problems (ROM sizes, RSDP)
> because the ACPI tables are split in two:
> 
> 1) fixed tables and the DSDT can be changed freely;
> 
> 2) tables that vary depending on the command-line arguments (SSDT,
> MADT, ...) are versioned and, given a machine type, they have to be
> byte-equivalent across QEMU versions >= 2.3.
> 
> Patches 5 and 6 introduce a new sizing algorithm.  Patch 7 use it
> to fix the migration problems.
> 
> Only the first 4 or 6 patches are meant for inclusion.  Patch 7 should
> only be committed after Igor's series that rewrites the templating
> mechanism in C.  That makes it much simpler to track changes to the ACPI
> tables, and removes dependencies on the IASL version that could cause
> some head-scratching.
> 
> The conflicts with Igor's series are nontrivial but overall
> not complicated to solve.  Igor rewrote ssdt-misc in C, but those
> parts can be easily removed from his series.  He has plans to
> build the DSDT from C, and if that materializes it can apply to
> acpi-dsdt-common.dsl too.

Oops, this does not update the bios-tables-test.  v2 next week or after
New Year.

Paolo