linux-kernel - Re: [PATCH] iommu/vt-d: Remove an unnecessary call set_dma

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Message-ID: <5543e3a5-dda5-49b5-aa59-fbc599d24bab@linux.intel.com>
Date: Thu, 10 Apr 2025 10:59:51 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Petr Tesařík <petr@...arici.cz>, iommu@...ts.linux.dev
Cc: Petr Tesarik <ptesarik@...e.com>, David Woodhouse <dwmw2@...radead.org>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>, Tom Murphy <murphyt7@....ie>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Remove an unnecessary call set_dma_ops()

On 4/9/25 23:44, Petr Tesařík wrote:
> On Thu,  3 Apr 2025 18:56:05 +0200
> Petr Tesarik<ptesarik@...e.com> wrote:
> 
>> Do not touch per-device DMA ops when the driver has been converted to use
>> the dma-iommu API.
>>
>> Fixes: c588072bba6b ("iommu/vt-d: Convert intel iommu driver to the iommu ops")
>> Signed-off-by: Petr Tesarik<ptesarik@...e.com>
> Does anyone agree? Or see any issues?

This change looks good to me. The iommu driver should not call
set_dma_ops() anyway. I will queue this for v6.15-rc.

I ever wondered whether we could clean up dev->dma_iommu when the device
is released by the iommu core. But, iommu_release_device() is only
called in the device removal path, so keeping dev->dma_iommu set doesn't
impose any functional impact AFAICS.

Thanks,
baolu