Message-ID: <abe55a65-1ab9-39ca-2cca-3190c6ba2e21@huawei.com>
Date:   Wed, 15 Feb 2023 11:05:11 +0800
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Subject: Re: [PATCH v3] x86/kdump: Handle blocked NMIs interrupt to avoid
 kdump crashes
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To:     Baoquan He <bhe@redhat.com>, Peter Zijlstra <peterz@infradead.org>
CC:     <mingo@redhat.com>, <bp@alien8.de>, <jroedel@suse.de>,
        <vbabka@suse.cz>, <hpa@zytor.com>, <tglx@linutronix.de>,
        <eric.devolder@oracle.com>, <tiwai@suse.de>,
        <keescook@chromium.org>, <dave.hansen@linux.intel.com>,
        <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
        <liwei391@huawei.com>, <xiexiuqi@huawei.com>,
        <kexec@lists.infradead.org>
References: <20230202014053.3604176-1-zengheng4@huawei.com>
 <Y9t9wvQ0HRwCs1Xh@hirez.programming.kicks-ass.net>
 <e57ba121-5bcc-e63b-691d-3e3d998e9e48@huawei.com>
 <Y+tZE8ixmlIDYrOu@hirez.programming.kicks-ass.net>
 <Y+wu5UJTzVIYrsbK@MiWiFi-R3L-srv>
From:   Zeng Heng <zengheng4@huawei.com>
In-Reply-To: <Y+wu5UJTzVIYrsbK@MiWiFi-R3L-srv>
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在 2023/2/15 9:01, Baoquan He 写道:
> Add kexec list to CC.
>
> On 02/14/23 at 10:49am, Peter Zijlstra wrote:
>> On Tue, Feb 14, 2023 at 05:30:46PM +0800, Zeng Heng wrote:
>>
>>>> I never remember the shutdown paths -- do we force wipe the PMU
>>>> registers somewhere before this?
>>> I have checked the panic process, and there is no wipe operation for PMU
>>> registers,
>>>
>>> which causes the watchdog bites.
>>>
>>> Do you mean we should directly disable PMU registers instead of calling
>>> `iret_to_self` to
>>>
>>> consume blocked NMI interrupts ?
>> If you don't wipe the PMU, there will be many and continuous NMIs, a
>> single IRET-to-SELF isn't going to safe you.
>>
>> Anyway, I had a bit of a grep around and I find we have:
>>
>>    kernel/events/core.c:   register_reboot_notifier(&perf_reboot_notifier);
>>
>> which should end up killing all the PMU activity. Somewhere around there
>> there's also a CONFIG_KEXEC_CORE ifdef, so I'm thinking it gets called
>> on the panic->crash-kernel path too?
> No, reboot_notifier_list is only handled in kexec reboot/reboot path,
> please see kernel_restart_prepare() invocation. Kdump path only shutdown
> key component like cpu, interrupt controller.

I would replace iret_to_self() with perf_event_exit_cpu() in kdump shutdown

path (in native_machine_crash_shutdown()).


After test, I would send v4 later.

Thanks all,

Zeng Heng