linux-kernel - Re: [PATCH v3 0/5] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

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Date:   Mon, 12 Feb 2018 12:06:10 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>, <linux-kernel@...r.kernel.org>,
        <ebiederm@...ssion.com>
CC:     <mingo@...nel.org>, <tglx@...utronix.de>, <x86@...nel.org>,
        <joro@...tes.org>, <uobergfe@...hat.com>, <prarit@...hat.com>
Subject: Re: [PATCH v3 0/5] x86/apic: Fix restoring boot irq mode in reboot
 and kexec/kdump

Hi all,

One thing confused me.

The disconnect_bsp_APIC() may restore the interrupt delivery mode into
virtual wire mode. it uses the vector F as the spurious interrput, But,
IMO, using the vector 0xFF(SPURIOUS_APIC_VECTOR) may more suitable and
will give us more detail. Why the disconnect_bsp_APIC() use vector F
here?

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 25ddf02598d2..550deaad6a9a 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2130,7 +2130,7 @@ void disconnect_bsp_APIC(int virt_wire_setup)
         value = apic_read(APIC_SPIV);
         value &= ~APIC_VECTOR_MASK;
         value |= APIC_SPIV_APIC_ENABLED;
-       value |= 0xf;
+       value |= SPURIOUS_APIC_VECTOR;
         apic_write(APIC_SPIV, value);

         if (!virt_wire_setup) {

Thanks,
	dou

At 02/09/2018 08:10 PM, Baoquan He wrote:
> A regression bug was introduced in below commit.
> commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")
> 
> It caused the action to fail which we try to restore boot irq mode
> in reboot and kexec/kdump. Details can be seen in patch 0002.
> 
> Warning can always be seen during kdump kernel boot on qemu/kvm
> platform. Our customer even saw casual kdump kernel hang once in
> ~30 attempts during stress testing of kdump on KVM machine.
> 
> This is v3 post, patches are rearranged and changed according to
> Eric's suggestions.
> 
> Baoquan He (5):
>    x86/apic: Split out restore_boot_irq_mode from disable_IO_APIC
>    x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump
>    x86/apic: Remove useless disable_IO_APIC
>    x86/apic: Rename variable/function related to x86_io_apic_ops
>    x86/apic: Set up through-local-APIC on boot CPU if 'noapic' specified
> 
>   arch/x86/include/asm/io_apic.h     |  9 +++++----
>   arch/x86/include/asm/x86_init.h    |  8 ++++----
>   arch/x86/kernel/apic/apic.c        |  2 +-
>   arch/x86/kernel/apic/io_apic.c     | 16 ++++------------
>   arch/x86/kernel/crash.c            |  3 ++-
>   arch/x86/kernel/machine_kexec_32.c |  7 +++----
>   arch/x86/kernel/machine_kexec_64.c |  7 +++----
>   arch/x86/kernel/reboot.c           |  3 ++-
>   arch/x86/kernel/x86_init.c         |  6 +++---
>   arch/x86/xen/apic.c                |  2 +-
>   drivers/iommu/irq_remapping.c      |  4 ++--
>   11 files changed, 30 insertions(+), 37 deletions(-)
>