linux-kernel - Re: [PATCH v2 01/16] iommu: introduce bind_pasid

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Date:   Tue, 10 Oct 2017 15:14:33 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        Lan Tianyu <tianyu.lan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>, Liu@...tes.org,
        Yi L <yi.l.liu@...ux.intel.com>
Subject: Re: [PATCH v2 01/16] iommu: introduce bind_pasid_table API function

Hi Jacob,

On Thu, Oct 05, 2017 at 04:03:29PM -0700, Jacob Pan wrote:
> +int iommu_unbind_pasid_table(struct iommu_domain *domain, struct device *dev)
> +{
> +	if (unlikely(!domain->ops->unbind_pasid_table))
> +		return -EINVAL;
> +
> +	return domain->ops->unbind_pasid_table(domain, dev);
> +}
> +EXPORT_SYMBOL_GPL(iommu_unbind_pasid_table);

Are there other reasons to let the unbind fail? Otherwise I'd suggest to
just make this a void function. Also not sure what the user of this
function should do when the unbind really fails.

> +enum pasid_table_model {
> +	PASID_TABLE_FORMAT_HOST,

What is this FORMAT_HOST for?

> +	PASID_TABLE_FORMAT_ARM_1LVL,
> +	PASID_TABLE_FORMAT_ARM_2LVL,
> +	PASID_TABLE_FORMAT_AMD,
> +	PASID_TABLE_FORMAT_INTEL,
> +};
> +
> +/**
> + * PASID table data used to bind guest PASID table to the host IOMMU. This will
> + * enable guest managed first level page tables.
> + * @version: for future extensions and identification of the data format
> + * @bytes: size of this structure
> + * @base_ptr:	PASID table pointer
> + * @pasid_bits:	number of bits supported in the guest PASID table, must be less
> + *		or equal than the host table size.
> + * @model:	PASID table format for different IOMMU models
> + */
> +struct pasid_table_config {
> +	__u32 version;

Can you also add a define for the version number? Userspace needs it to
initialize the struct and the kernel to check against it.

> +	__u32 bytes;
> +	__u64 base_ptr;
> +	__u8 pasid_bits;
> +	enum pasid_table_model model;
> +	union {
> +		struct {
> +			/* Intel specific fields */
> +		} intel;
> +
> +		struct {
> +			/* ARM specific fields */
> +			bool pasid0_dma_no_pasid;
> +		} arm;
> +
> +		struct {
> +			/* AMD specific fields */
> +		} amd;

Thinking more about this, we can omit the sub-structs for models that
don't need them. For the amd-model for example the base_ptr and
pasid_bits fields are sufficient.


Regards,

	Joerg