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

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Message-ID: <20190226111743.GK20740@8bytes.org>
Date:   Tue, 26 Feb 2019 12:17:43 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Jean-Philippe Brucker <jean-philippe.brucker@....com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        christian.koenig@....com, kevin.tian@...el.com,
        jacob.jun.pan@...ux.intel.com, ashok.raj@...el.com,
        baolu.lu@...ux.intel.com, alex.williamson@...hat.com
Subject: Re: [PATCH 1/1] iommu: Bind process address spaces to devices

Hi Jean-Philippe,

Thanks for the patch! I think this is getting close to be applied after
the next merge window.

On Wed, Feb 20, 2019 at 02:27:59PM +0000, Jean-Philippe Brucker wrote:
> +int iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, int *pasid,
> +			  iommu_mm_exit_handler_t mm_exit, void *drvdata)

I think we are better of with introducing a sva-bind handle which can be
used to extend and further configure the binding done with this
function.

How about a 'struct iommu_sva' with an iommu-private definition that is
returned by this function:

	struct iommu_sva *iommu_sva_bind_device(struct device *dev,
						struct mm_struct *mm);

and the corresponding unbind function:

	int iommu_sva_unbind_device(struct iommu_sva* *handle);

(Btw, does this need to return and int? Can unbinding fail?).

With that in place we can implement and extentable API base on the
handle:

	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);

I think at least the AMD IOMMU driver needs more call-backs like a
handler that is invoked when a fault can not be resolved. And there
might be others in the future, putting them all in the parameter list of
the bind function doesn't scale well.

Regards,

	Joerg