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 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
Why ACPICA interpreter is acting so differently from this definition? This
is because, there are many software entropies preventing this from being
enabled, such entropies need to be cleaned up first in order not to trigger
regressions for specific platforms. These entropies include:
1. ECDT support is broken. In fact, the original EC driver was correct, but
devlopers started to use the namespace EC instead of ECDT just because
several broken ECDT tables were reported on the bugzilla. They trusted
the namespace EC settings rather than the ECDT ones, this led to the
evaluation of _REG/_GPE/_CRS and namespace walk before executing the
module level AML opcodes. And the fixes in fact finally disable early EC
usages (used during table loading and early device enumeration
processes).
2. _REG evaluations are wrong. ACPICA provides APIs for OSPMs to register
operation region handlers. But for the early operation region accesses,
ACPI spec declares that the evaluations of _REG are not required, but
the ACPICA APIs do not avoid running _REG to meet this early
requirements. Code to fix this is partially upstreamed during previous
ACPICA release cycle.
3. _REG associations are wrong. ACPICA associates _REG control method to
all operation region objects before executing the _REG control method.
This can happen even when a control method is evaluated and operation
regions defined in the method is initialized
(acpi_ev_initialize_region). As a part of the ACPICA internal _REG
evaluation state machine, it requires the namespace walk, and all
namespace walk should be ensured to happen only "AFTER THE NAMESPACE IS
INITIALIZED". But when this logic happens during the table loading, it
may fail in finding the _REG method since the _REG method may not be
created by the interpreter just because _REG is defined after the
operation region object's declaration.
4. _REG(CONNECT)/_REG(DISCONNECT) executions are not balanced, this can
lead to wrong table loading/unloading results. Since _REG evaluations
require the releasing of all interpreter/namespace locks in order to
allow another evaluation to happen, and ACPICA operand object
destruction code can be invoked from different locking environment, this
becomes difficult for the developers to provide one single function to
make _REG(CONNECT)/_REG(DISCONNECT) balanced.
5. \_SB._INI is not the first control method evaluated by the interpreter.
Many platforms put initialization code in \_SB._INI in order to have
named objects initialized very early during the device enumeration
process. Without this order strictly ensured, early operation region
access enabling could break these platforms.
6. Linux initialization order is wrong, it is now:
a. load namespace without executing root scope If/Else/While module
level code blocks;
b. probe ECDT and instal EmbeddedControl operation region handler with
_REG evaluated;
c. install SystemMemory, SystemIo, PciConfig operation region handlers
without evaluating _REG;
d. run _REG for SystemMemory, SystemIo, PciConfig operation regions;
e. execute root scope If/Else/While module level code blocks;
f. enable GPE and namespace EC.
While the correct order should be:
a. probe ECDT and install EmbeddedControl operation region handler
without evaluating _REG;
b. install SystemMemory, SystemIo, PciConfig operation region handlers
without evaluating _REG;
c. load namespace, in the meanshile, execute all module level AML
opcodes;
d. run _REG for SystemMemory, SystemIo, PciConfig operation regions;
e. enable GPE and namespace EC which results in _REG evaluation for EC.
Until now we've upstreamed most of the entropy fixes into the Linux kernel,
tested the grammar switch in the ACPICA upstream using ASLTS and no
significant regressions can be seen while we need more tests before it is
merged:
https://github.com/acpica/acpica/pull/134
This is the ASLTS running result after applying the grammar switch, the
test cases include new "module" case for which ACPICA interpreter cannot
pass without this grammar switch applied:
============================================================
Test cases specified for running:
arithmetic
bfield
constant
control
descriptor
logic
manipulation
name
reference
region
synchronization
table
misc
provoke
oarg
oconst
olocal
onamedloc
onamedglob
opackageel
oreftonamed
oreftopackageel
oreturn
rstore
roptional
rcopyobject
rindecrement
rexplicitconv
badasl
namespace
exc
exc_ref
exc_operand2
exc_result2
exc_tbl
mt_mutex
extra
extra_aslts
bdemo
bdemof
condbranches
TOTAL: (32-bit norm mode)
PASS : 0
FAIL : 0
BLOCKED : 0
SKIPPED : 0
Tests : 0
Test Cases : 40 (of 47)
Test Collections : 7 (of 8)
Outstanding allocations after execution : 0
Outstanding allocations (ACPI Error) : 0
Large Reference Count (ACPI Error) : 0
Memory consumption total : 0 Kb
TOTAL: (64-bit norm mode)
PASS : 0
FAIL : 0
BLOCKED : 0
SKIPPED : 0
Tests : 0
Test Cases : 40 (of 47)
Test Collections : 7 (of 8)
Outstanding allocations after execution : 0
Outstanding allocations (ACPI Error) : 0
Large Reference Count (ACPI Error) : 0
Memory consumption total : 0 Kb
TOTAL: (32-bit slack mode)
PASS : 0
FAIL : 0
BLOCKED : 0
SKIPPED : 0
Tests : 0
Test Cases : 40 (of 47)
Test Collections : 7 (of 8)
Outstanding allocations after execution : 0
Outstanding allocations (ACPI Error) : 0
Large Reference Count (ACPI Error) : 0
Memory consumption total : 0 Kb
TOTAL: (64-bit slack mode)
PASS : 0
FAIL : 0
BLOCKED : 0
SKIPPED : 0
Tests : 0
Test Cases : 40 (of 47)
Test Collections : 7 (of 8)
Outstanding allocations after execution : 0
Outstanding allocations (ACPI Error) : 0
Large Reference Count (ACPI Error) : 0
Memory consumption total : 0 Kb
============================================================
Since we need more tests from the real users, we could make the grammar
switch released from the Linux upstream. It's safe to do so because we have
implemented regression protection (acpi_gbl_parse_table_as_term_list) in
the fixes. The earlier the fix is tested by more real users, the better
quality can be achieved by knowing the unknown cases (if any).
Lv Zheng (4):
ACPICA: Dispatcher: Fix an issue that the opregions created by the
linked MLC were not tracked
ACPICA: ACPI 2.0, Interpreter: Fix MLC issues by switching to new
TermList grammar for table loading
ACPI 2.0 / AML: Enable correct ACPI subsystem initialization order
for new table loading mode
ACPI 2.0 / AML: Fix module level execution by correctly parsing table
as TermList
drivers/acpi/acpica/acnamesp.h | 3 +
drivers/acpi/acpica/acparser.h | 2 +
drivers/acpi/acpica/dsopcode.c | 6 ++
drivers/acpi/acpica/evrgnini.c | 3 +-
drivers/acpi/acpica/exconfig.c | 6 +-
drivers/acpi/acpica/nsload.c | 3 +-
drivers/acpi/acpica/nsparse.c | 163 ++++++++++++++++++++++++++++++++--------
drivers/acpi/acpica/psparse.c | 4 +-
drivers/acpi/acpica/psxface.c | 73 ++++++++++++++++++
drivers/acpi/acpica/tbxfload.c | 3 +-
drivers/acpi/acpica/utxfinit.c | 3 +-
drivers/acpi/bus.c | 6 +-
include/acpi/acpixf.h | 6 ++
13 files changed, 241 insertions(+), 40 deletions(-)
--
1.7.10
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
