linux-kernel - Re: [PATCH v1 2/9] ACPI: processor: idle: Return failure if entry method is not buffer or integer type

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Message-ID: <8c0057a7-24a2-493a-8054-904a89ca9f6d@huawei.com>
Date: Thu, 23 Oct 2025 17:25:07 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: <lenb@...nel.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Sudeep.Holla@....com>,
	<linuxarm@...wei.com>, <jonathan.cameron@...wei.com>,
	<zhanjie9@...ilicon.com>, <zhenglifeng1@...wei.com>, <yubowen8@...wei.com>
Subject: Re: [PATCH v1 2/9] ACPI: processor: idle: Return failure if entry
 method is not buffer or integer type


在 2025/10/22 3:34, Rafael J. Wysocki 写道:
> On Mon, Sep 29, 2025 at 11:38 AM Huisong Li <lihuisong@...wei.com> wrote:
>> According to ACPI spec, entry method in LPI sub-package must be buffer
>> or integer. However, acpi_processor_evaluate_lpi() regeards it as success
>> and treat it as an effective LPI state.
> Is that the case?  AFAICS, it just gets to the next state in this case
> and what's wrong with that?
The flatten_lpi_states() would consider the state with illegal entry 
method sub-package as a valid one
if the flag of this state is enabled(ACPI_LPI_STATE_FLAGS_ENABLED is set).
And then cpuidle governor would use it because the caller of 
acpi_processor_ffh_lpi_probe() also don't see the return value.
>
>> This is unreasonable and needs to
>> return failure to prevent other problems from occurring.
>>
>> Fixes: a36a7fecfe60 ("ACPI / processor_idle: Add support for Low Power Idle(LPI) states")
>> Signed-off-by: Huisong Li <lihuisong@...wei.com>
>> ---
>>   drivers/acpi/processor_idle.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>> index 5acf12a0441f..681587f2614b 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -958,7 +958,9 @@ static int acpi_processor_evaluate_lpi(acpi_handle handle,
>>                          lpi_state->entry_method = ACPI_CSTATE_INTEGER;
>>                          lpi_state->address = obj->integer.value;
>>                  } else {
>> -                       continue;
>> +                       pr_err("Entry method in LPI sub-package must be buffer or integer.\n");
>> +                       ret = -EINVAL;
>> +                       goto end;
>>                  }
>>
>>                  /* elements[7,8] skipped for now i.e. Residency/Usage counter*/
>> --