Re: [PATCH] ACPICA: Detect duplicate SSDT tables

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 28-02-17 06:19, Zheng, Lv wrote:
> Hi,
>
>> From: Hans de Goede [mailto:hdegoede@redhat.com]
>> Subject: [PATCH] ACPICA: Detect duplicate SSDT tables
>>
>> Some machines have the exact (byte for byte) same SSDT tables multiple
>> times in the root_table_list.
>
> Could you give a machine list here?

Currently I'm seeing this on a GPD win machine:

http://www.gpd.hk/gpdwin.asp

I thought I was seeing it on more machines, but those have
different apci table loading errors...

>> Detect this and silently skip the duplicates
>> rather then printing a scary looking set of errors.
>
> Why will this matter to OSPMs?

Not sure what you mean with OSPMs but I can tell you why this
matters in general, Linux distributions like e.g. Fedora have
been putting a lot of work in a smooth boot experience where
end users do not get any scary text messages. For some more
embedded like systems this even is a hard requirement.

The kernel supports quiet kernel cmdline argument to silence
normal kernel messages, which is part of what is needed but
messages with a log level of error still get shown, breaking
the "no scary text messages" product requirement.

> And should we add non-costless steps just in order to reduce errors,

Yes we should, work on that front has been happening for years,
also the CPU cost of this check is quite small, memcmp will
only happen on identically sized tables and even then it will
exit as soon as a single byte differs.

> while the errors are on the contrary useful (in1dicating platform issues)?

These errors are useful for developers / during testing but
not in production setups, esp. in the case of duplicate tables
where not loading the duplicate leads to 0 bad side effects.

I've an alternative proposal though, since this check just fixes
a small part of the early boot messages caused by SSDT loading
and since the code itself chooses to ignore any errors:

         /* Ignore errors while loading tables, get as many as possible */

How about setting a global flag while loading these tables and making

ACPI_EXCEPTION calls log the exceptions with a log level of warning
as well as turning the final:

                 ACPI_ERROR((AE_INFO,
                             "%u table load failures, %u successful",
                             tables_failed, tables_loaded));

Into a warning ?

Regards,

Hans




>
> Thanks
> Lv
>
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  drivers/acpi/acpica/tbxfload.c | 41 ++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 40 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/acpica/tbxfload.c b/drivers/acpi/acpica/tbxfload.c
>> index 82019c0..1971cd7 100644
>> --- a/drivers/acpi/acpica/tbxfload.c
>> +++ b/drivers/acpi/acpica/tbxfload.c
>> @@ -125,6 +125,44 @@ ACPI_EXPORT_SYMBOL_INIT(acpi_load_tables)
>>
>>  /*******************************************************************************
>>   *
>> + * FUNCTION:    acpi_tb_find_duplicate_ssdt
>> + *
>> + * PARAMETERS:  table         - validated acpi_table_desc of table to check
>> + *              index         - index of table to find a duplicate of
>> + *
>> + * RETURN:      TRUE if a duplicate is found, FALSE if not
>> + *
>> + * DESCRIPTION: Private helper function for acpi_tb_load_namespace to
>> + *              avoid trying to load duplicate ssdt tables
>> + *
>> + ******************************************************************************/
>> +static u8 acpi_tb_find_duplicate_ssdt(struct acpi_table_desc *table, u32 index)
>> +{
>> +	struct acpi_table_desc *dup;
>> +	u32 i;
>> +
>> +	for (i = 0; i < index; ++i) {
>> +		dup = &acpi_gbl_root_table_list.tables[i];
>> +
>> +		if (!acpi_gbl_root_table_list.tables[i].address ||
>> +		    (!ACPI_COMPARE_NAME(dup->signature.ascii, ACPI_SIG_SSDT)
>> +		     && !ACPI_COMPARE_NAME(dup->signature.ascii,
>> +					   ACPI_SIG_PSDT)
>> +		     && !ACPI_COMPARE_NAME(dup->signature.ascii,
>> +					   ACPI_SIG_OSDT))
>> +		    || ACPI_FAILURE(acpi_tb_validate_table(dup))
>> +		    || dup->length != table->length) {
>> +			continue;
>> +		}
>> +
>> +		if (memcmp(dup->pointer, table->pointer, table->length) == 0)
>> +			return TRUE;
>> +	}
>> +	return FALSE;
>> +}
>> +
>> +/*******************************************************************************
>> + *
>>   * FUNCTION:    acpi_tb_load_namespace
>>   *
>>   * PARAMETERS:  None
>> @@ -212,7 +250,8 @@ acpi_status acpi_tb_load_namespace(void)
>>  					   ACPI_SIG_PSDT)
>>  		     && !ACPI_COMPARE_NAME(table->signature.ascii,
>>  					   ACPI_SIG_OSDT))
>> -		    || ACPI_FAILURE(acpi_tb_validate_table(table))) {
>> +		    || ACPI_FAILURE(acpi_tb_validate_table(table))
>> +		    || acpi_tb_find_duplicate_ssdt(table, i)) {
>>  			continue;
>>  		}
>>
>> --
>> 2.9.3
>