linux-kernel - Re: [PATCH RFC v2 0/3] Add set_dev_data and unset_dev

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Date:   Fri, 21 Apr 2023 10:37:22 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Tian, Kevin" <kevin.tian@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "will@...nel.org" <will@...nel.org>,
        "joro@...tes.org" <joro@...tes.org>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 0/3] Add set_dev_data and unset_dev_data support

On Fri, Apr 21, 2023 at 10:09:35AM -0300, Jason Gunthorpe wrote:
> On Fri, Apr 21, 2023 at 01:20:13AM -0700, Nicolin Chen wrote:
> 
> > +/**
> > + * struct iommufd_device_set_data - ioctl(IOMMU_DEVICE_SET_DATA)
> > + * @size: sizeof(struct iommufd_device_set_data)
> > + * @dev_id: The device to set a device data
> > + * @data_uptr: User pointer of the device user data.
> > + * @data_len: Length of the device user data.
> > + */
> > +struct iommufd_device_set_data {
> > +	__u32 size;
> > +	__u32 dev_id;
> > +	__aligned_u64   data_uptr;
> > +	__u32 data_len;
> > +};
> > +#define IOMMU_DEVICE_SET_DATA _IO(IOMMUFD_TYPE, IOMMUFD_CMD_DEVICE_SET_DATA)
> > +
> > +/**
> > + * struct iommufd_device_unset_data - ioctl(IOMMU_DEVICE_UNSET_DATA)
> > + * @size: sizeof(struct iommufd_device_unset_data)
> > + * @dev_id: The device to unset its device data
> > + */
> > +struct iommufd_device_unset_data {
> > +	__u32 size;
> > +	__u32 dev_id;
> > +};
> > +#define IOMMU_DEVICE_UNSET_DATA _IO(IOMMUFD_TYPE, IOMMUFD_CMD_DEVICE_UNSET_DATA)
> > 
> > Maybe just like this?
> 
> How would the iommu_ops backing this work?

How about the following piece? Needs a test with QEMU though..

static const size_t iommufd_device_data_size[] = {
	[IOMMU_HW_INFO_TYPE_NONE] = 0,
	[IOMMU_HW_INFO_TYPE_INTEL_VTD] = 0,
	[IOMMU_HW_INFO_TYPE_ARM_SMMUV3] =
		sizeof(struct iommu_device_data_arm_smmuv3),
};

int iommufd_device_set_data(struct iommufd_ucmd *ucmd)
{
	struct iommufd_device_set_data *cmd = ucmd->cmd;
	struct iommufd_device *idev;
	const struct iommu_ops *ops;
	void *data = NULL;
	u32 klen = 0;
	int rc;

	if (!cmd->data_uptr || !cmd->data_len)
		return -EINVAL;

	idev = iommufd_get_device(ucmd, cmd->dev_id);
	if (IS_ERR(idev))
		return PTR_ERR(idev);

	ops = dev_iommu_ops(idev->dev);
	if (!ops || !ops->set_dev_data_user || !ops->unset_dev_data_user ||
	    ops->hw_info_type >= ARRAY_SIZE(iommufd_device_data_size)) {
		rc = -EOPNOTSUPP;
		goto out_put_idev;
	}

	klen = iommufd_device_data_size[ops->hw_info_type];
	if (!klen) {
		rc = -EOPNOTSUPP;
		goto out_put_idev;
	}

	data = kzalloc(klen, GFP_KERNEL);
	if (!data) {
		rc = -ENOMEM;
		goto out_put_idev;
	}

	if (copy_struct_from_user(data, klen, u64_to_user_ptr(cmd->data_uptr),
				  cmd->data_len)) {
		rc = -EFAULT;
		goto out_free_data;
	}

	rc = ops->set_dev_data_user(idev->dev, data);
out_free_data:
	kfree(data);
out_put_idev:
	iommufd_put_object(&idev->obj);
	return rc;
}