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Message-ID: <42b53bff-4027-4cb6-a457-e26fd62895e5@linux.intel.com>
Date: Tue, 23 Jan 2024 08:55:28 +0800
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Cc: baolu.lu@linux.intel.com, =?UTF-8?B?SsO2cmcgUsO2ZGVs?= <joro@8bytes.org>,
 Will Deacon <will@kernel.org>, iommu@lists.linux.dev,
 linux-kernel@vger.kernel.org
Subject: Re: DMAR-IR: IRQ remapping was enabled on dmar6 but we are not in
 kdump mode
To: Paul Menzel <pmenzel@molgen.mpg.de>
References: <5517f76a-94ad-452c-bae6-34ecc0ec4831@molgen.mpg.de>
 <433452d0-589a-49c8-8044-dcc93d5be90a@linux.intel.com>
 <24bf9a11-6abd-4ccf-9ca1-3cf75c45d374@molgen.mpg.de>
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From: Baolu Lu <baolu.lu@linux.intel.com>
In-Reply-To: <24bf9a11-6abd-4ccf-9ca1-3cf75c45d374@molgen.mpg.de>
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On 2024/1/22 22:53, Paul Menzel wrote:
> Am 22.01.24 um 13:38 schrieb Baolu Lu:
>> On 2024/1/19 22:45, Paul Menzel wrote:
>>>
>>> On a Dell PowerEdge T640, Linux 5.9 and 6.6.12 warn about kdump:
>>>
>>>      [    2.728445] DMAR-IR: IRQ remapping was enabled on dmar6 but 
>>> we are not in kdump mode
>>>      [    2.736544] DMAR-IR: IRQ remapping was enabled on dmar5 but 
>>> we are not in kdump mode
>>>      [    2.744620] DMAR-IR: IRQ remapping was enabled on dmar4 but 
>>> we are not in kdump mode
>>>      [    2.752695] DMAR-IR: IRQ remapping was enabled on dmar3 but 
>>> we are not in kdump mode
>>>      [    2.760774] DMAR-IR: IRQ remapping was enabled on dmar2 but 
>>> we are not in kdump mode
>>>      [    2.768847] DMAR-IR: IRQ remapping was enabled on dmar1 but 
>>> we are not in kdump mode
>>>      [    2.776922] DMAR-IR: IRQ remapping was enabled on dmar0 but 
>>> we are not in kdump mode
>>>      [    2.784999] DMAR-IR: IRQ remapping was enabled on dmar7 but 
>>> we are not in kdump mode
>>>
>>> Looking through the logs, this only happens when using kexec to 
>>> restart the system.
>>
>> The code that warned this is,
>>
>>   599         if (ir_pre_enabled(iommu)) {
>>   600                 if (!is_kdump_kernel()) {
>>   601                         pr_warn("IRQ remapping was enabled on %s 
>> but we are not in kdump mode\n",
>>   602                                 iommu->name);
>>   603                         clear_ir_pre_enabled(iommu);
>>   604                         iommu_disable_irq_remapping(iommu);
>>   605                 }
>>
>> The VT-d interrupt remapping is enabled during boot, but this is not a
>> kdump kernel.
>>
>> Do you mind checking whether the disable interrupt remapping callback
>> was called during kexec reboot?
>>
>> 1121 struct irq_remap_ops intel_irq_remap_ops = {
>> 1122         .prepare                = intel_prepare_irq_remapping,
>> 1123         .enable                 = intel_enable_irq_remapping,
>> 1124         .disable                = disable_irq_remapping,
>> 1125         .reenable               = reenable_irq_remapping,
>> 1126         .enable_faulting        = enable_drhd_fault_handling,
>> 1127 };
> 
> Is there a way to check this without rebuilding the Linux kernel?

I am not sure, but you can check whether any messages are dumped in the
path of .disable callback? or try to use ftrace?

Best regards,
baolu