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



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