Re: [PATCH v3 04/15] iommu: Move bus setup to IOMMU device registration

From: Baolu Lu <baolu.lu@linux.intel.com>
To: Robin Murphy <robin.murphy@arm.com>, joro@8bytes.org
Cc: baolu.lu@linux.intel.com, will@kernel.org, iommu@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	suravee.suthikulpanit@amd.com, vasant.hegde@amd.com,
	mjrosato@linux.ibm.com, gerald.schaefer@linux.ibm.com,
	schnelle@linux.ibm.com, linux-s390@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 04/15] iommu: Move bus setup to IOMMU device registration
Date: Wed, 6 Jul 2022 10:35:22 +0800	[thread overview]
Message-ID: <d6a8e85b-ab7d-f5c9-a8cb-79dd8e68c967@linux.intel.com> (raw)
In-Reply-To: <5b9b608af21b3c4353af042355973bac55397962.1657034828.git.robin.murphy@arm.com>

On 2022/7/6 01:08, Robin Murphy wrote:
> @@ -202,12 +210,32 @@ int iommu_device_register(struct iommu_device *iommu,
>   	spin_lock(&iommu_device_lock);
>   	list_add_tail(&iommu->list, &iommu_device_list);
>   	spin_unlock(&iommu_device_lock);
> +
> +	for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++) {
> +		struct bus_type *bus = iommu_buses[i];
> +		int err;
> +
> +		if (bus->iommu_ops && bus->iommu_ops != ops) {
> +			err = -EBUSY;
> +		} else {
> +			bus->iommu_ops = ops;
> +			err = bus_iommu_probe(bus);
> +		}
> +		if (err) {
> +			iommu_device_unregister(iommu);
> +			return err;
> +		}
> +	}
> +
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(iommu_device_register);

With bus_set_iommu() retired, my understanding is that now we embrace
the first-come-first-serve policy for bus->iommu_ops setting. This will
lead to problem in different iommu_ops for different bus case. Did I
overlook anything?

Best regards,
baolu

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