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

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Message-ID: <20190226130204.GA23259@8bytes.org>
Date:   Tue, 26 Feb 2019 14:02:04 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>
Cc:     kevin.tian@...el.com, alex.williamson@...hat.com,
        ashok.raj@...el.com, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, christian.koenig@....com
Subject: Re: [PATCH 1/1] iommu: Bind process address spaces to devices

On Tue, Feb 26, 2019 at 12:49:15PM +0000, Jean-Philippe Brucker wrote:
> On 26/02/2019 11:17, Joerg Roedel wrote:
> > 	int iommu_sva_get_pasid(struct iommu_sva *handle);
> > 	void iommu_sva_set_exit_handler(struct iommu_sva *handle,
> > 					iommu_mm_exit_handler_t mm_exit);
> 
> Ok sounds good. It doesn't look like this interface requires a lot of
> changes on my side (iommu_sva corresponds to the iommu_bond structure
> I've been using internally) but I might find problems while implementing it.

Great!

> Device drivers will also want to have some private data to easily
> identify the faulting or exiting context. How about:
> 
>     struct iommu_sva_ops {
>         void (*mm_exit)(struct iommu_sva *handle, void *drvdata);
>     };
>     int iommu_sva_set_ops(struct iommu_sva *handle,
>                           const struct iommu_sva_ops *ops,
>                           void *drvdata);

Okay, we can also do it this way. But then please pass the drvdata via
the bind() call and not via set_ops(). Set_ops() should then really only
pass the call-backs, as the name implies.

> I now think that device driver should always call unbind() to release
> the iommu_sva handle, even if they got notified by mm_exit.

Yes, this should be required. I think it also makes driver
implementation easier because it doesn't need to care too much about
this special case.

Regards,

	Joerg