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

From: Dou Liyang
Date: Wed Mar 29 2017 - 23:10:10 EST




At 03/30/2017 11:03 AM, Dou Liyang wrote:
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.


ahh,

--cc joro@xxxxxxxxxx, not joro@xxxxxxxxxx

Thanks
Liyang

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