linux-kernel - Re: [RESEND PATCH 0/3] x86/apic/kexec: Enable legacy irq mode before jump to kexec/kdump kernel

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Date:   Thu, 11 Jan 2018 10:05:32 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org, fenghua.yu@...el.com,
        ebiederm@...ssion.com, mingo@...hat.com, tglx@...utronix.de,
        hpa@...or.com
Cc:     x86@...nel.org, rostedt@...dmis.org, jgross@...e.com,
        peterz@...radead.org, uobergfe@...hat.com, joro@...tes.org
Subject: Re: [RESEND PATCH 0/3] x86/apic/kexec: Enable legacy irq mode before
 jump to kexec/kdump kernel

Hi all,

PING!

(Add Fenghua and Eric to this thread)

On 01/05/18 at 11:42am, Baoquan He wrote:
> On kvm guest, the latest kernel will always print warning during kdump kernel boots
> as below. The reaons is the legacy irq mode is disabled before jump to kexec/kdump
> kernel. So in setup_local_APIC(), the do { xxx } while (queued && max_loops > 0)
> can't handle if pending irq exists in APIC IRR since LAPIC is disabled. It will
> terminate the do while loop finally when max_loops overflows by subtraction. Then
> WARN_ON(max_loops <= 0) is triggered.
> 
> [    0.001000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1467 setup_local_APIC+0x228/0x330
> [    0.001000] Modules linked in:
> [    0.001000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc5+ #3
> [    0.001000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014
> [    0.001000] RIP: 0010:setup_local_APIC+0x228/0x330
> [    0.001000] RSP: 0000:ffffffffb6e03eb8 EFLAGS: 00010286
> [    0.001000] RAX: 0000009edb4c4d84 RBX: 0000000000000000 RCX: 00000000b099d800
> [    0.001000] RDX: 0000009e00000000 RSI: 0000000000000000 RDI: 0000000000000810
> [    0.001000] RBP: 0000000000000000 R08: ffffffffffffffff R09: 0000000000000001
> [    0.001000] R10: ffff98ce6a801c00 R11: 0761076d072f0776 R12: 0000000000000001
> [    0.001000] R13: 00000000000000f0 R14: 0000000000004000 R15: ffffffffffffc6ff
> [    0.001000] FS:  0000000000000000(0000) GS:ffff98ce6bc00000(0000) knlGS:0000000000000000
> [    0.001000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.001000] CR2: 00000000ffffffff CR3: 0000000022209000 CR4: 00000000000406b0
> [    0.001000] Call Trace:
> [    0.001000]  apic_bsp_setup+0x56/0x74
> [    0.001000]  x86_late_time_init+0x11/0x16
> [    0.001000]  start_kernel+0x3c9/0x486
> [    0.001000]  secondary_startup_64+0xa5/0xb0
> [    0.001000] Code: 00 85 c9 74 2d 0f 31 c1 e1 0a 48 c1 e2 20 41 89 cf 4c 03 7c 24 08 48 09 d0 49 29 c7 4c 89 3c 24 48 83 3c 24 00 0f 8f 8f fe ff ff <0f> ff e9 10 ff ff ff 48 83 2c 24 01 eb e7 48 83 c4 18 5b 5d 41 
> [    0.001000] ---[ end trace b88e71b9a6ebebdd ]---
> [    0.001000] masked ExtINT on CPU#0
> 
> With patch 2/3 applied, the above warning disappeared. And with patch 2/3
> applied, the issue mentioned in patch 1/3 can also be fixed because the LAPIC
> has been set as ExtINT before jump to kdump kernel, while we had better set it
> explicitly. Seems no reason not to enable legacy irq mode before jump to
> kexec/kdump kernel, and can make it be consistent with normal kernel.
> 
> Patch 3/3 is doing clean up, I am fine if people think it's unnecessary.
> 
> 
> Baoquan He (3):
>   x86/apic: Set up through LAPIC on boot CPU's LINT0 if ioapic is
>     disabled
>   x86/apic/kexec: Enable legacy irq mode before jump to kexec/kdump
>     kernel
>   x86/apic: Clean up the names of legacy irq mode setting related
>     functions
> 
>  arch/x86/include/asm/apic.h        |  2 +-
>  arch/x86/include/asm/io_apic.h     |  6 +++---
>  arch/x86/kernel/apic/apic.c        | 13 +++++++------
>  arch/x86/kernel/apic/io_apic.c     | 25 ++++++++++++-------------
>  arch/x86/kernel/crash.c            |  2 +-
>  arch/x86/kernel/machine_kexec_32.c | 15 +++++----------
>  arch/x86/kernel/machine_kexec_64.c | 15 +++++----------
>  arch/x86/kernel/reboot.c           |  2 +-
>  arch/x86/kernel/x86_init.c         |  2 +-
>  drivers/iommu/irq_remapping.c      |  2 +-
>  10 files changed, 37 insertions(+), 47 deletions(-)
> 
> -- 
> 2.5.5
>