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Date: Tue, 26 May 2015 13:13:09 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] Why *.dsl files exist in qemu project?
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To: Zhi Yong Wu <zwu.kernel@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>



On 26/05/2015 13:06, Zhi Yong Wu wrote:
> HI,
> 
> Does anyone know why these *.dsl files exist in qemu project? Since
> these files are used to define some hardware resource and operation
> methods tables, i thought that they should be in the bios related
> project, right?
> 
> $ls -l hw/i386/*.dsl
> -rw-rw-r-- 1 admin admin  3872 May 26 10:43 hw/i386/acpi-dsdt-cpu-hotplug.dsl
> -rw-rw-r-- 1 admin admin  1470 May 26 10:43 hw/i386/acpi-dsdt-dbug.dsl
> -rw-rw-r-- 1 admin admin 11284 May 26 10:43 hw/i386/acpi-dsdt.dsl
> -rw-rw-r-- 1 admin admin  1673 May 26 10:43 hw/i386/acpi-dsdt-hpet.dsl
> -rw-rw-r-- 1 admin admin  3682 May 26 10:43 hw/i386/acpi-dsdt-isa.dsl
> -rw-rw-r-- 1 admin admin  3826 May 26 10:43 hw/i386/acpi-dsdt-pci-crs.dsl
> -rw-rw-r-- 1 admin admin 16347 May 26 10:43 hw/i386/q35-acpi-dsdt.dsl
> -rw-rw-r-- 1 admin admin  2948 May 26 10:43 hw/i386/ssdt-mem.dsl
> -rw-rw-r-- 1 admin admin 10677 May 26 10:43 hw/i386/ssdt-misc.dsl
> -rw-rw-r-- 1 admin admin  3490 May 26 10:43 hw/i386/ssdt-pcihp.dsl
> -rw-rw-r-- 1 admin admin  2351 May 26 10:43 hw/i386/ssdt-proc.dsl

These describe the hardware, which changes as QEMU gets new abilities.
So QEMU is exporting the ACPI tables to the firmware.  The firmware
reads them.

This eliminates code duplication: for example OVMF, SeaBIOS, CoreBoot
and now qboot all can use the same ACPI tables and only implement a very
small loader (~100 lines of code) based on fw_cfg.

Paolo