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

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Message-ID: <4571f444-01ca-45e4-8465-745e16c1b73d@amd.com>
Date: Wed, 29 Oct 2025 16:18:53 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Jörg Rödel <joro@...tes.org>
Cc: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>,
 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



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.


-Vasant