Date:   Sat, 24 Sep 2016 02:32:39 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lv Zheng <lv.zheng@...el.com>, Len Brown <len.brown@...el.com>
Cc:     Lv Zheng <zetalog@...il.com>, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v5 0/5] ACPI 2.0: Stop defer-executing module level code

On Friday, September 23, 2016 11:26:26 AM Lv Zheng wrote:
> After fixing ACPICA internal locking issues, we can enable the correct
> grammar support for the table loading. The new grammar treats the entire
> table as TermList rather than ObjectList, thus the module level code should
> be executed right in place.
> 
> MLC (module level code) is an ACPICA terminology describing the AML code
> out of any control method, currently only Type1Opcode (If/Else/While)
> wrapped MLC code blocks are executed by the AML interpreter after the table
> loading. But the issue which is fixed by this patchset is:
>    Not only Type1Opcode, but also Type2Opcode will be executed as MLC and
>    MLC is not defer-executed after loading the table, but is executed right
>    in place.
> 
> The following AML code is assembled into a static loading SSDT, and used
> as an instrumentation to pry into the de-facto standard AML interpreter
> behaviors:
>   Name (ECOK, Zero)
>   Scope (\)
>   {
>       DBUG ("TermList 1")
>       If (LEqual (ECOK, Zero))
>       {
>           DBUG ("TermList 2")
>           Device (MDEV)
>           {
>               DEBUG (TermList 3")
>               If (CondRefOf (MDEV))
>               {
>                   DBUG ("MDEV exists")
>               }
>               If (CondRefOf (MDEV._STA))
>               {
>                   DBUG ("MDEV._STA exists")
>               }
>               If (CondRefOf (\_SB.PCI0.EC))
>               {
>                   DBUG ("\\_SB.PCI0.EC exists")
>               }
>               Name (_HID, EisaId ("PNP9999"))
>               Method (_STA, 0, Serialized)
>               {
>                   DEBUG ("\\_SB.MDEV._STA")
>                   Return (0x0F)
>               }
>           }
>           DBUG ("TermList 4")
>       }
>       Method (_INI, 0, Serialized)
>       {
>           DBUG ("\\_SB._INI")
>       }
>   }
>   Scope (_SB.PCI0)
>   {
>       Device (EC)
>       {
>           ...
>       }
>   }
> The DBUG function is a function to write the debugging messages into a
> SystemIo debug port.
> Running Windows with the BIOS providing this SSDT via RSDT, the following
> messages are obtained from the debug port:
>   TermList 1
>   TermList 2
>   TermList 3
>   \_SB.MDEV exists
>   TermList 4
>   \_SB._INI
>   ...
> 
> This test reveals the de-facto grammar for the AMLCode to us:
> 1. During the table loading, MLC will be executed by the interpreter, this
>    is partially supported by the current ACPICA;
> 2. For SystemIo, not only after the _REG(1, 1) is evaluated (current ACPICA
>    interpreter limitation), but when the table is being loaded, the
>    SystemIo (the debugging port) is accessible, this is recently fixed in
>    the upstream, now all early operation regions are accessible during the
>    table loading;
> 3. Not only Type1Opcode, but also Type2Opcode will be executed as MLC and
>    MLC is not executed after loading the table, but is executed right in
>    place, the Linux upstream is not compliant to this behavior.
> 
> The last compliance issue has already been clarified in ACPI 2.0
> specification, so the compliance issue is not that Linux is not compliant
> to the de-facto standard OS, but that Linux is not compliant to ACPI 2.0.
> Definition block tables in fact is defined by the spec as TermList, which
> has no difference than the control methods, thus the interpretion of the
> table should be no difference that the control method evaluation:
>      AMLCode := DefBlockHeader TermList
>      DefMethod := MethodOp PkgLength NameString MethodFlags TermList
> Now the new upcoming ACPI specification has been clarified around the above
> grammar primitives, so we need to implement them for Linux.
> 
> This patchset also contains 2 required fixes generated to fix the
> regressions detected by the ACPICA ASLTS tool. The ASLTS 'table' test suite
> has detected such regressions. The fixes have been accepted by the ACPICA
> upstream (please refer to the ACPICA upstream URL in the description of the
> 2 patches). And they are sent to Linux community as urgent materials along
> with the module level code enabling series. With the additional regression
> fixes, new grammar changes have passed all ASLTS 'table' cases:
>   https://bugs.acpica.org/show_bug.cgi?id=1327
>   https://github.com/acpica/acpica/pull/177
> 
> Lv Zheng (5):
>   ACPICA: Tables: Fix "UNLOAD" code path lock issues
>   ACPICA: Parser: Fix a regression in LoadTable support
>   ACPI 2.0 / AML: Enable correct ACPI subsystem initialization order
>     for new table loading mode
>   ACPI 2.0 / AML: Improve module level execution by moving the
>     If/Else/While execution to per-table basis
>   ACPI 2.0 / AML: Fix module level execution by correctly parsing table
>     as TermList

[1-2/5] queued up for 4.9.

The rest I'd prefer to keep in linux-next for some time before they go in,
so let's make them 4.10 material if not urgent for some reasons.

Thanks,
Rafael

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