Re: [PATCH] acpi/tests/bios-tables-test: add an environment variable for iasl location

[Michael S. Tsirkin]

On Wed, May 17, 2023 at 04:43:53PM +0000, Bernhard Beschow wrote:
> 
> 
> Am 17. Mai 2023 12:07:51 UTC schrieb Ani Sinha <anisinha@redhat.com>:
> >Currently the meson based QEMU build process locates the iasl binary from the
> >current PATH and other locations [1] and uses that to set CONFIG_IASL which 
> >is
> >then used by the test.
> >
> >This has two disadvantages:
> > - If iasl was not previously installed in the PATH, one has to install iasl
> >   and rebuild QEMU in order to pick up the iasl location. One cannot simply
> >   use the existing bios-tables-test binary because CONFIG_IASL is only set
> >   during the QEMU build time by meson and then bios-tables-test has to be
> >   rebuilt with CONFIG_IASL set in order to use iasl.
> > - Sometimes, the stock iasl that comes with distributions is simply not good
> >   enough because it does not support the latest ACPI changes - newly
> >   introduced tables or new table attributes etc. In order to test ACPI code
> >   in QEMU, one has to clone the latest acpica upstream repository and
> >   rebuild iasl in order to get support for it. In those cases, one may want
> >   the test to use the iasl binary from a non-standard location.
> >
> >In order to overcome the above two disadvantages, we introduce a new
> >environment variable IASL_PATH that can be set by the tester pointing to an
> >possibly non-standard iasl binary location.
> 
> Why not add a submodule -- like we do with dtc -- and use that? Then
> we could possibly convert the ACPI blobs used in bios-tables-test into
> text files which would make AML patches a bit more comprehensible. We
> also didn't have to trust the commit messages to contain the actual
> change because one would see it right in the patch.
> 
> Best regards,
> Bernhard

Yea people dislike submodules but I guess we could come up
with something. I stumbled upon git-subrepo recently
but did not try it yet.

There's a long list of issues unrelated to having iasl installed though:
- IASL disassembler output is unstable, tends to change
  with each revision
- IASL disassembler lacks (or used to, last time I looked)
  support for all hosts that QEMU wants to support
  (e.g. I think it is still somewhat broken on BE)
- Tends to crash in weird ways on unexected ACPI

I talked to ACPICA guys about guarateed output with some flag
and they were uninterested.
We used to have expected ASL in git, was a little easier for
contributors but a pain for maintainers and users.

-- 
MST