linux-kernel - Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier

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Date:   Fri, 28 Jul 2017 10:28:34 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     "Zheng, Lv" <lv.zheng@...el.com>, "bhe@...hat.com" <bhe@...hat.com>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "izumi.taku@...fujitsu.com" <izumi.taku@...fujitsu.com>,
        "tokunaga.keiich@...fujitsu.com" <tokunaga.keiich@...fujitsu.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Julian Wollrath <jwollrath@....de>
Subject: Re: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization
 earlier

Hi, Zheng

At 07/28/2017 09:53 AM, Zheng, Lv wrote:
[...]
>>
>>> Dmar hardware support interrupt remapping and io remapping separately. But
>>> intel_iommu_init() is called later than intel_prepare_irq_remapping().
>>> So what if make dmar_table_init() a reentrant function? You can just
>>> have a try, but maybe not a good idea, the dmar table will be parsed
>>> twice.
>>
>> Yes, It is precisely one reason that I gave up invoking
>> acpi_put_table().
>
> Parsing a table twice is not a problem on x86.
> If you check the code, there are many examples.
> It's actually required if you want to use a table both in early stage and late stage.
>

I am sorry I don't explain clearly.

Yeah, in current kernel, The DMAR table has been parsed twice as well.
one is in detect_intel_iommu(), the other is in dmar_table_init().

Here we focus on the reentrant dmar_table_init(), this func contains
many callback for parsing different DMAR type structures, such as DRHD,
RMRR.

acpi_put_table() can release the mapped DMAR address, but we should
clear the remapping structure types manually. and I think parsing these
DMAR type structures again may have an influence on interrupt remapping.


Thanks,

	dou.

> Thanks
>
>>
>> Thanks,
>>
>> 	dou.
>>
>>>
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> 	dou.
>>>>>
>>>>> Thanks
>>>>> Lv
>>>>>
>>>>>> From: Dou Liyang [mailto:douly.fnst@...fujitsu.com]
>>>>>> Sent: Friday, July 14, 2017 1:53 PM
>>>>>> To: x86@...nel.org; linux-kernel@...r.kernel.org
>>>>>> Cc: tglx@...utronix.de; mingo@...nel.org; hpa@...or.com; ebiederm@...ssion.com; bhe@...hat.com;
>>>>>> peterz@...radead.org; izumi.taku@...fujitsu.com; tokunaga.keiich@...fujitsu.com; Dou Liyang
>>>>>> <douly.fnst@...fujitsu.com>; linux-acpi@...r.kernel.org; Rafael J. Wysocki <rjw@...ysocki.net>;
>> Zheng,
>>>>>> Lv <lv.zheng@...el.com>; Julian Wollrath <jwollrath@....de>
>>>>>> Subject: [PATCH v7 12/13] ACPI / init: Invoke early ACPI initialization earlier
>>>>>>
>>>>>> Linux uses acpi_early_init() to put the ACPI table management into
>>>>>> the late stage from the early stage where the mapped ACPI tables is
>>>>>> temporary and should be unmapped.
>>>>>>
>>>>>> But, now initializing interrupt delivery mode should map and parse the
>>>>>> DMAR table earlier in the early stage. This causes an ACPI error when
>>>>>> Linux reallocates the ACPI root tables. Because Linux doesn't unmapped
>>>>>> the DMAR table after using in the early stage.
>>>>>>
>>>>>> Invoke acpi_early_init() earlier before late_time_init(), Keep the DMAR
>>>>>> be mapped and parsed in late stage like before.
>>>>>>
>>>>>> Reported-by: Xiaolong Ye <xiaolong.ye@...el.com>
>>>>>> Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
>>>>>> Cc: linux-acpi@...r.kernel.org
>>>>>> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
>>>>>> Cc: Zheng, Lv <lv.zheng@...el.com>
>>>>>> Cc: Julian Wollrath <jwollrath@....de>
>>>>>> ---
>>>>>> Test in my own PC(Lenovo M4340).
>>>>>> Ask help for doing regression testing for the bug said in commit c4e1acbb35e4
>>>>>> ("ACPI / init: Invoke early ACPI initialization later").
>>>>>>
>>>>>>  init/main.c | 2 +-
>>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/init/main.c b/init/main.c
>>>>>> index df58a41..7a09467 100644
>>>>>> --- a/init/main.c
>>>>>> +++ b/init/main.c
>>>>>> @@ -654,12 +654,12 @@ asmlinkage __visible void __init start_kernel(void)
>>>>>>  	kmemleak_init();
>>>>>>  	setup_per_cpu_pageset();
>>>>>>  	numa_policy_init();
>>>>>> +	acpi_early_init();
>>>>>>  	if (late_time_init)
>>>>>>  		late_time_init();
>>>>>>  	calibrate_delay();
>>>>>>  	pidmap_init();
>>>>>>  	anon_vma_init();
>>>>>> -	acpi_early_init();
>>>>>>  #ifdef CONFIG_X86
>>>>>>  	if (efi_enabled(EFI_RUNTIME_SERVICES))
>>>>>>  		efi_enter_virtual_mode();
>>>>>> --
>>>>>> 2.5.5
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>>
>>
>
>
>
>