linux-kernel - Re: [PATCH] iommu/amd: Enhance "Completion-wait Time-out" error message

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Message-ID: <12665f0a-0a1f-48c3-8d07-b982064097ae@amd.com>
Date: Wed, 29 Oct 2025 16:46:21 +0530
From: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>
To: Vasant Hegde <vasant.hegde@....com>, Jörg Rödel
	<joro@...tes.org>
CC: <will@...nel.org>, <robin.murphy@....com>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <suravee.suthikulpanit@....com>,
	<Santosh.Shukla@....com>
Subject: Re: [PATCH] iommu/amd: Enhance "Completion-wait Time-out" error
 message

Hi Joerg and Vasant,

On 10/29/2025 4:18 PM, Vasant Hegde wrote:
> 
> 
> On 10/29/2025 2:00 PM, Jörg Rödel wrote:
>> On Tue, Oct 28, 2025 at 02:45:16PM +0530, Vasant Hegde wrote:
>>> We have debugfs support to extract entire command buffer. Also many cases once
>>> we hit completion wait timeout, buffer won't progress.. and we will hit
>>> completion wait repetitively. Hence in V2 he has removed printing entire command
>>> buffer.
>>>
>>> Do you want to log entire buffer once to dmesg if amd_iommu_dump=1 ? (for first
>>> completion wait timeout event).
>>
>> I think there is some value in printing the command buffer contents at the
>> point in time when the timeout happens. When it is read later from debug-fs,
>> the state of the command buffer might already be different, making debugging
>> harder.
> 
> Ack. if amd_iommu_dump=1 then we can log entire command buffer to dmesg once.
> 

Sure. I’ll send an updated version for review.

Thanks
Dheeraj

> 
> -Vasant
>