linux-kernel - Re: [PATCH v4 3/3] iommu: Drop sw_msi from iommu

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Message-ID: <Z+GK98/VSvYl518j@nvidia.com>
Date: Mon, 24 Mar 2025 13:40:23 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Nicolin Chen <nicolinc@...dia.com>, kevin.tian@...el.com,
	robin.murphy@....com, joro@...tes.org, will@...nel.org,
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] iommu: Drop sw_msi from iommu_domain

On Mon, Mar 24, 2025 at 09:25:58AM -0700, Nathan Chancellor wrote:

> I bisected a loss of networking on one of my machines to this change as
> commit e009e088d88e ("iommu: Drop sw_msi from iommu_domain") in -next.

Okay wow, I will drop this series from the tree if I don't see a
resolution in a few days. We can try again next cycle, thank you for
testing and bisect!

> At this change, I see:
> 
>   [  +0.000000] Linux version 6.14.0-rc2-00033-ge009e088d88e (nathan@...62) (aarch64-linux-gcc (GCC) 14.2.0, GNU ld (GNU Binutils) 2.42) #1 SMP PREEMPT_DYNAMIC Mon Mar 24 08:57:49 MST 2025
>   ...
>   [  +0.002355] fsl_mc_bus NXP0008:00: Adding to iommu group 0
>   [  +0.000533] fsl_mc_bus NXP0008:00: MC firmware version: 10.28.1
>   [  +0.002565] fsl_mc_dprc dprc.1: DMA mask not set
>   [  +0.019255] fsl_mc_dprc dprc.1: Adding to iommu group 1
>   [  +0.046820] fsl_mc_dprc dprc.1: Failed to allocate IRQs

I guess it is tripping up going through iommu_dma_prepare_msi()
somehow?

Maybe fsl bus is special and doesn't manage to set
IOMMU_COOKIE_DMA_IOVA for some reason?

I wonder if this is not right:

+               default:
+                       ret = -EOPNOTSUPP;
+                       break;

And it should be just break instead (return 0) which is what was
happening before?

Jason