linux-kernel - Re: DMAR-IR: IRQ remapping was enabled on dmar6 but we are not in kdump mode

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Date: Mon, 22 Jan 2024 15:53:06 +0100
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Jörg Rödel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: DMAR-IR: IRQ remapping was enabled on dmar6 but we are not in
 kdump mode

Dear Baolu,


Than you for your reply.


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?

Do you have access to server hardware and are able to test kexec?


Kind regards,

Paul