linux-kernel - Re: [PATCH v2 1/1] iommu: Bind process address spaces to devices

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Date:   Mon, 1 Apr 2019 11:10:23 +0100
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     kevin.tian@...el.com, alex.williamson@...hat.com,
        ashok.raj@...el.com, zhangfei.gao@...mail.com,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        christian.koenig@....com
Subject: Re: [PATCH v2 1/1] iommu: Bind process address spaces to devices

Hi Joerg,

On 25/03/2019 14:44, Joerg Roedel wrote:
> Hey Jean-Philippe,
> 
> thanks for the patch, I think we are on the finish line with this
> interface. Just one small question below.
> 
> On Wed, Mar 20, 2019 at 03:02:58PM +0000, Jean-Philippe Brucker wrote:
>> +int iommu_sva_set_ops(struct iommu_sva *handle,
>> +		      const struct iommu_sva_ops *sva_ops)
>> +{
>> +	const struct iommu_ops *ops = handle->dev->bus->iommu_ops;
>> +
>> +	if (!ops || !ops->sva_set_ops)
>> +		return -ENODEV;
>> +
>> +	return ops->sva_set_ops(handle, sva_ops);
>> +}
> 
> What is the purpose of the sva_set_ops call-back in iommu-ops? Is the
> IOMMU driver supposed to do some extra setup work with the provided ops?
> Otherwise we can just store the pointer in 'struct iommu_sva' without
> calling into the iommu driver.

Right that would be simpler. I added the sva_set_ops callback so that
IOMMU driver can use the same lock in unbind() and sva_set_ops(). But I
think it's safe to assume that device drivers don't call unbind() before
setting the ops.

Thanks,
Jean