Re: [Qemu-devel] [PATCH 0/3] merge SSDT into DSDT

[Igor Mammedov]

On Mon, 25 Jan 2016 15:01:36 +0200
"Michael S. Tsirkin" <address@hidden> wrote:

> On Mon, Jan 25, 2016 at 12:57:28PM +0100, Igor Mammedov wrote:
> > On Sun, 24 Jan 2016 08:32:23 +0200
> > "Michael S. Tsirkin" <address@hidden> wrote:
> >   
> > > On Fri, Jan 22, 2016 at 03:36:05PM +0100, Igor Mammedov wrote:  
> > > > Merging both tables will allow for futher ASL
> > > > simplification and cleanups per device/subsystem
> > > > And it also allows to reduce number of expected
> > > > binary blobs for ACPI tests which reduces tests
> > > > maintenance.  
> > > 
> > > What this does break, however, is adding XSDT which
> > > we might need to do in the future.
> > > I'd rather do the reverse and have as much as possible
> > > in the SSDT.  
> > It doesn't forbid us adding XSDT later,  
> 
> Right but we'll have to duplicate dsdt in xsdt, right?
nope, DSDT is pointed by FADT while SSDTs by RSDT/XSDT.

The only reason why we have DSDT/SSDT split now is that
DSDT used to be static while SSDT generated dynamically.
Now when both tables are dynamically generated there
is no point to keep them separate.

I don't see any benefit in keeping empty DSDT as you
suggest with all the content in SSDT, it the same as
having only DSDT table but we have to maintain 2 tables
in code and tests.
If at some point we use XSDT to hide non XP compatible
ASL (if that works at all) then SSDT is the place where
that non compat ASL should be put and pointed only by XSDT,
while the the rest of compatible code should stay in 
the main mandatory table (i.e. DSDT).

> 
> > DSDT should be kept XP compatible as it's more or less now
> > and incompatible features we could put in their own SSDTs
> > if we decide to go for XSDT approach to hide them form XP.
> > For example I plan to move cpu/memory hotplug ASL into separate
> > SSDTs and continue to simplify DSDT on top of this series.  
> 
> So I'm kind of confused. Why move hotplug to dsdt then move
> them back out to an SSDT? Let's just put everything in an
> SSDT ...
because right now cpu/mem hotplug ASL is split between both
tables so the first step to isolating and consolidating scattered
parts is to put everything into one table. After that it
will be more easy to verify changes that refactoring will
introduce using bios-tables-test and should simplify refactoring
patches and review.

As for moving hotplug into dedicated SSDTs, it's for purpose
of sharing that code with ARM target and later we possible
could use it also to hide XP incompatible ASL in them by
referencing them from only XSDT.

Why do you insist on putting everything into SSDT instead of DSDT?

> 
> > >   
> > > > Boot tested with RHEL72, WS2003, WS2012R2 guests.
> > > > 
> > > > git tree for testing:
> > > > https://github.com/imammedo/qemu.git merge_ssdt_into_dsdt_v1 
> > > > 
> > > > Igor Mammedov (3):
> > > >   pc: acpi: merge SSDT into DSDT
> > > >   tests: pc: acpi: drop not needed 'expected SSDT' blobs
> > > >   tests: pc: acpi: add expected DSDT.bridge blobs and update DSDT
> > > > blobs
> > > > 
> > > >  hw/i386/acpi-build.c                 | 246
> > > > ++++++++++++++++-------------------
> > > > tests/acpi-test-data/pc/DSDT         | Bin 3028 -> 5478 bytes
> > > > tests/acpi-test-data/pc/DSDT.bridge  | Bin 0 -> 7337 bytes
> > > > tests/acpi-test-data/pc/SSDT         | Bin 2486 -> 0 bytes
> > > > tests/acpi-test-data/pc/SSDT.bridge  | Bin 4345 -> 0 bytes
> > > > tests/acpi-test-data/q35/DSDT        | Bin 7666 -> 8321 bytes
> > > > tests/acpi-test-data/q35/DSDT.bridge | Bin 0 -> 8338 bytes
> > > > tests/acpi-test-data/q35/SSDT        | Bin 691 -> 0 bytes
> > > > tests/acpi-test-data/q35/SSDT.bridge | Bin 708 -> 0 bytes 9 files
> > > > changed, 111 insertions(+), 135 deletions(-) create mode 100644
> > > > tests/acpi-test-data/pc/DSDT.bridge delete mode 100644
> > > > tests/acpi-test-data/pc/SSDT delete mode 100644
> > > > tests/acpi-test-data/pc/SSDT.bridge create mode 100644
> > > > tests/acpi-test-data/q35/DSDT.bridge delete mode 100644
> > > > tests/acpi-test-data/q35/SSDT delete mode 100644
> > > > tests/acpi-test-data/q35/SSDT.bridge
> > > > 
> > > > -- 
> > > > 1.8.3.1  
> > >   
>