linux-kernel - Re: [RFC PATCH 0/6] Unify the Interrupt Mode and setup it as soon as possible

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Date:   Thu, 30 Mar 2017 11:03:18 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <tglx@...utronix.de>, <mingo@...nel.org>, <ebiederm@...ssion.com>,
        <hpa@...or.com>, <izumi.taku@...fujitsu.com>, <joro@...pes.org>
Subject: Re: [RFC PATCH 0/6] Unify the Interrupt Mode and setup it as soon as
 possible

Hi Baoquan,

At 03/30/2017 10:08 AM, Baoquan He wrote:
> Hi Liyang,
>
> This is awesome. I planned to do this after kaslr back porting, glad to
> see your posting. I like below diagram and the idea of patch 2/6
> framework. Will review and see what I can do to help since rhel bug from
> FJ is assigned to me.
>

Thanks very much for your join! We have investigated the bug almost
half a year. :)

In my opinion,
If we plan to refactor the process of APIC initialization for the bug.
There must be lots of work need to be done. This patchset is just the
first step. When I test it, I am thinking about:

1. The check and logic in each enable and setup LAPIC/IOAPIC functions.
2. The process of IRQ remapping.
3. The check and init of APIC timer.
4. The relationship between the various switches, such as If
the smp_found_config is 1, the acpi_lapic must be 1.

And following work to me are:

1. Use more test cases to test.
2. learn the IOMMU.
3. trace the APIC timer code.
4. make the check logic more clear.

Hope to be helpful to you.

> Thanks for the effort!
>
> And add Joerg to this thread since he knows IOMMU very well.

oops, Yes, I forgot it, Thanks!

Thanks
Liyang

>
> Thanks
> Baoquan
>
> On 03/29/17 at 10:55pm, Dou Liyang wrote:
>> According to Ingo's and Eric's advice[1,2], Try my best to optimize the
>> init of Interrupt Mode for x86.
>>
>> The MP specification defines three different interrupt modes as follows:
>>
>>  1. PIC Mode
>>  2. Virtual Wire Mode
>>  3. Symmetic I/O Mode
>>
>> Currently, In kernel,
>>
>> 1. Setup the Virtual Wire Mode during the IRQ initialization(
>> step 1 in the following figure).
>> 2. Enable and Setup the Symmetic I/O Mode either during the
>> SMP-capabe system prepares CPUs(step 2) or during the UP system
>> initializes itself(step 3).
>>
>>   start_kernel
>> +---------------+
>> |
>> +--> .......
>> |
>> |    setup_arch
>> +--> +-------+
>> |
>> |    init_IRQ
>> +-> +--+-----+
>> |      |        init_ISA_irqs
>> |      +------> +-+--------+
>> |                 |         +----------------+
>> +--->             +------>  | 1.init_bsp_APIC|
>> |     .......               +----------------+
>> +--->
>> |     rest_init
>> +--->---+-----+
>> |       |   kernel_init
>> |       +> ----+-----+
>> |              |   kernel_init_freeable
>> |              +->  ----+-------------+
>> |                       |     smp_prepare_cpus
>> |                       +---> +----+---------+
>> |                       |          |   +-------------------+
>> |                       |          +-> |2.  apic_bsp_setup |
>> |                       |              +-------------------+
>> |                       |
>> v                       |     smp_init
>>                         +---> +---+----+
>>                                   |    +-------------------+
>>                                   +--> |3.  apic_bsp_setup |
>>                                        +-------------------+
>>
>> The purpose of this patchset is Unifing these setup steps and executing as
>> soon as possible as follows:
>>
>>    start_kernel
>> ---------------+
>> |
>> |
>> |
>> |     init_IRQ
>> +---->---+----+
>> |        |
>> |        |      +--------------------+
>> |        +----> | 4. init_bsp_APIC   |
>> |               +--------------------+
>> v
>>
>> By the way, Also fix a bug about kexec[3].
>>
>>
>> Some doubts, need help:
>>
>> 1. Patchset has influence on IOMMU in enable_IR_x2apic(). Not sure
>> it can be in advance?
>>
>> 2. Due to
>>
>> Commit 8c3ba8d04924 ("x86, apic: ack all pending irqs when crashed/on kexec")
>>
>>  ..., patchset also needs TSC and uses the "cpu_khz" in setup_local_APIC().
>> And a warning[4] will be triggered when crashed/on kexec. Not sure how to
>> modify?
>>
>> [1]. https://lkml.org/lkml/2016/8/2/929
>> [2]. https://lkml.org/lkml/2016/8/1/506
>> [3]. https://lkml.org/lkml/2016/7/25/1118
>> [4]. WARN_ON(max_loops <= 0) in setup_local_APIC()
>>
>> Dou Liyang (6):
>>   x86/apic: Replace init_bsp_APIC() with apic_virture_wire_mode_setup()
>>   x86/apic: Construct a framework for setuping APIC mode as soon as
>>     possible
>>   x86/apic: Extract APIC timer related code from apic_bsp_setup()
>>   x86/apic: Make the APIC mode setup earlier for SMP-capable system
>>   x86/apic: Make the APIC mode setup earlier for UP system
>>   x86/apic: Remove the apic_virture_wire_mode_setup()
>>
>>  arch/x86/include/asm/apic.h    |   7 +-
>>  arch/x86/include/asm/io_apic.h |   2 +
>>  arch/x86/kernel/apic/apic.c    | 218 ++++++++++++++++++++++++-----------------
>>  arch/x86/kernel/apic/io_apic.c |   4 +-
>>  arch/x86/kernel/irqinit.c      |   6 +-
>>  arch/x86/kernel/smpboot.c      |  68 ++-----------
>>  6 files changed, 149 insertions(+), 156 deletions(-)
>>
>> --
>> 2.5.5
>>
>>
>>
>
>
>