linux-kernel - Re: [PATCH v13 09/13] iommu/sva: Refactoring iommu_sva_bind/unbind

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Message-ID: <Yxd2+d/VOjdOgrR2@myrica>
Date:   Tue, 6 Sep 2022 17:36:09 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 09/13] iommu/sva: Refactoring
 iommu_sva_bind/unbind_device()

On Tue, Sep 06, 2022 at 08:44:54PM +0800, Lu Baolu wrote:
> +/**
> + * iommu_sva_bind_device() - Bind a process address space to a device
> + * @dev: the device
> + * @mm: the mm to bind, caller must hold a reference to mm_users
> + *
> + * Create a bond between device and address space, allowing the device to access
> + * the mm using the returned PASID. If a bond already exists between @device and
> + * @mm, it is returned and an additional reference is taken. Caller must call
> + * iommu_sva_unbind_device() to release each reference.

This isn't true anymore. How about storing handle in the domain?

(Maybe also drop my Reviewed-by tags since this has changed significantly,
I tend to ignore patches that have them)

Thanks,
Jean

> + *
> + * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
> + * initialize the required SVA features.
> + *
> + * On error, returns an ERR_PTR value.
> + */
> +struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> +{
> +	struct iommu_domain *domain;
> +	struct iommu_sva *handle;
> +	ioasid_t max_pasids;
> +	int ret;
> +
> +	max_pasids = dev->iommu->max_pasids;
> +	if (!max_pasids)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
> +	/* Allocate mm->pasid if necessary. */
> +	ret = iommu_sva_alloc_pasid(mm, 1, max_pasids - 1);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> +	if (!handle)
> +		return ERR_PTR(-ENOMEM);
> +
> +	mutex_lock(&iommu_sva_lock);
> +	/* Search for an existing domain. */
> +	domain = iommu_get_domain_for_dev_pasid(dev, mm->pasid,
> +						IOMMU_DOMAIN_SVA);
> +	if (IS_ERR(domain)) {
> +		ret = PTR_ERR(domain);
> +		goto out_unlock;
> +	}
> +
> +	if (domain) {
> +		domain->users++;
> +		goto out;
> +	}
> +
> +	/* Allocate a new domain and set it on device pasid. */
> +	domain = iommu_sva_domain_alloc(dev, mm);
> +	if (!domain) {
> +		ret = -ENOMEM;
> +		goto out_unlock;
> +	}
> +
> +	ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
> +	if (ret)
> +		goto out_free_domain;
> +	domain->users = 1;
> +out:
> +	mutex_unlock(&iommu_sva_lock);
> +	handle->dev = dev;
> +	handle->domain = domain;
> +
> +	return handle;
> +
> +out_free_domain:
> +	iommu_domain_free(domain);
> +out_unlock:
> +	mutex_unlock(&iommu_sva_lock);
> +	kfree(handle);
> +
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_bind_device);