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

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Date:   Tue, 18 Jul 2017 17:44:19 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     "bhe@...hat.com" <bhe@...hat.com>
CC:     "Zheng, Lv" <lv.zheng@...el.com>,
        "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 Baoquan,

At 07/18/2017 04:45 PM, bhe@...hat.com wrote:
> On 07/18/17 at 02:08pm, Dou Liyang wrote:
>> Hi, Zheng
>>
>> At 07/18/2017 01:18 PM, Zheng, Lv wrote:
>>> Hi,
>>>
>>> Can the problem be fixed by invoking acpi_put_table() for mapped DMAR table?
>>
>> Invoking acpi_put_table() is my first choice. But it made the kernel
>> *panic* when we try to get the table again in intel_iommu_init() in
>> late stage.
>>
>> I am also confused that:
>>
>> There are two places where we used DMAR table in Linux:
>>
>> 1) In detect_intel_iommu() in ACPI early stage:
>>
>> ...
>> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl);
>> ....
>> if (dmar_tbl) {
>> 	acpi_put_table(dmar_tbl);
>> 	dmar_tbl = NULL;
>> }
>>
>> 2) In dmar_table_init() in ACPI late stage:
>>
>> ...
>> status = acpi_get_table(ACPI_SIG_DMAR, 0, &dmar_tbl);
>> ...
>>
>> As we know, dmar_table_init() is called by intel_iommu_init() and
>> intel_prepare_irq_remapping().
>>
>> When I invoked acpi_put_table() in the intel_prepare_irq_remapping() in
>> early stage like 1) shows, kernel will panic.
>
> That's because acpi_put_table() will make the table pointer be NULL,
> while dmar_table_init() will skip parse_dmar_table() calling if
> dmar_table_initialized is set to 1 in intel_prepare_irq_remapping().
>

Correctly.

I have considered and removed the *dmar_table_initialized* in this
situation. So, dmar_table_init() didn't skip parse_dmar_table()
calling.

I didn't dig into the cause, I think it is interesting, I will do it
right now and share with you later.

> 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().

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
>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>>
>
>
>