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

[Dou Liyang]

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