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

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Date: Sat, 8 Jun 2024 13:07:15 +0200
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 Linux folks,


Am 15.05.24 um 08:02 schrieb Paul Menzel:

> Am 15.05.24 um 04:13 schrieb Baolu Lu:
>> On 5/15/24 3:46 AM, Paul Menzel wrote:
>>> Am 23.01.24 um 01:55 schrieb Baolu Lu:
>>>> 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?
>>>
>>> With
>>>
>>> ```
>>> diff --git a/drivers/iommu/intel/irq_remapping.c 
>>> b/drivers/iommu/intel/irq_remapping.c
>>> index 712ebfc9870c6..146f19ae5b5f1 100644
>>> --- a/drivers/iommu/intel/irq_remapping.c
>>> +++ b/drivers/iommu/intel/irq_remapping.c
>>> @@ -1030,6 +1030,7 @@ static void disable_irq_remapping(void)
>>>       struct dmar_drhd_unit *drhd;
>>>       struct intel_iommu *iommu = NULL;
>>>
>>> +     pr_warn("XXX: Called %s\n", __func__);
>>>       /*
>>>        * Disable Interrupt-remapping for all the DRHD's now.
>>>        */
>>> ```
>>>
>>> I can’t see anything in the logs, so it does not seem to be called.
>>>
>>> Can you reproduce the issue?
>>
>> How did you reproduce this?
> 
> On a “server” (with Intel Xeon?), in my case Dell PowerEdge T640 and 
> Dell PowerEdge R930 (Intel E7-8891 v3), run
> 
>      kexec /boot/bzImage --initrd=/boot/grub/initramfs.igz --reuse-cmdline

Were you able to fit some cycles into reproducing/analyzing this issue?


Kind regards,

Paul