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    Subject[PATCH v6 3/4] iommufd: Add IOMMU_GET_HW_INFO
    Date
    Under nested IOMMU translation, userspace owns the stage-1 translation
    table (e.g. the stage-1 page table of Intel VT-d or the context table
    of ARM SMMUv3, and etc.). Stage-1 translation tables are vendor specific,
    and need to be compatible with the underlying IOMMU hardware. Hence,
    userspace should know the IOMMU hardware capability before creating and
    configuring the stage-1 translation table to kernel.

    This adds IOMMU_GET_HW_INFO ioctl to query the IOMMU hardware information
    (a.k.a capability) for a given device. The returned data is vendor specific,
    userspace needs to decode it with the structure mapped by the @out_data_type
    field.

    As only physical devices have IOMMU hardware, so this will return error
    if the given device is not a physical device.

    Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
    Co-developed-by: Nicolin Chen <nicolinc@nvidia.com>
    Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
    Signed-off-by: Yi Liu <yi.l.liu@intel.com>
    ---
    drivers/iommu/iommufd/main.c | 97 ++++++++++++++++++++++++++++++++++++
    include/uapi/linux/iommufd.h | 36 +++++++++++++
    2 files changed, 133 insertions(+)

    diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
    index 94c498b8fdf6..54e61fbf56f8 100644
    --- a/drivers/iommu/iommufd/main.c
    +++ b/drivers/iommu/iommufd/main.c
    @@ -17,6 +17,7 @@
    #include <linux/bug.h>
    #include <uapi/linux/iommufd.h>
    #include <linux/iommufd.h>
    +#include "../iommu-priv.h"

    #include "io_pagetable.h"
    #include "iommufd_private.h"
    @@ -177,6 +178,99 @@ static int iommufd_destroy(struct iommufd_ucmd *ucmd)
    return 0;
    }

    +static int iommufd_zero_fill_user(void __user *ptr, size_t bytes)
    +{
    + int index = 0;
    +
    + for (; index < bytes; index++) {
    + if (put_user(0, (uint8_t __user *)(ptr + index)))
    + return -EFAULT;
    + }
    + return 0;
    +}
    +
    +static int iommufd_fill_hw_info(struct device *dev, void __user *user_ptr,
    + unsigned int *length, u32 *type)
    +{
    + const struct iommu_ops *ops;
    + unsigned int data_len;
    + void *data;
    + int rc = 0;
    +
    + ops = dev_iommu_ops(dev);
    + if (!ops->hw_info) {
    + *length = 0;
    + *type = IOMMU_HW_INFO_TYPE_NONE;
    + return 0;
    + }
    +
    + data = ops->hw_info(dev, &data_len, type);
    + if (IS_ERR(data))
    + return PTR_ERR(data);
    +
    + /*
    + * drivers that have hw_info callback should have a unique
    + * iommu_hw_info_type.
    + */
    + if (WARN_ON_ONCE(*type == IOMMU_HW_INFO_TYPE_NONE)) {
    + rc = -ENODEV;
    + goto err_free;
    + }
    +
    + *length = min(*length, data_len);
    + if (copy_to_user(user_ptr, data, *length)) {
    + rc = -EFAULT;
    + goto err_free;
    + }
    +
    +err_free:
    + kfree(data);
    + return rc;
    +}
    +
    +static int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
    +{
    + struct iommu_hw_info *cmd = ucmd->cmd;
    + unsigned int length = cmd->data_len;
    + struct iommufd_device *idev;
    + void __user *user_ptr;
    + u32 hw_info_type;
    + int rc = 0;
    +
    + if (cmd->flags || cmd->__reserved || !cmd->data_len)
    + return -EOPNOTSUPP;
    +
    + idev = iommufd_get_device(ucmd, cmd->dev_id);
    + if (IS_ERR(idev))
    + return PTR_ERR(idev);
    +
    + user_ptr = u64_to_user_ptr(cmd->data_ptr);
    +
    + rc = iommufd_fill_hw_info(idev->dev, user_ptr,
    + &length, &hw_info_type);
    + if (rc)
    + goto err_put;
    +
    + /*
    + * Zero the trailing bytes if the user buffer is bigger than the
    + * data size kernel actually has.
    + */
    + if (length < cmd->data_len) {
    + rc = iommufd_zero_fill_user(user_ptr + length,
    + cmd->data_len - length);
    + if (rc)
    + goto err_put;
    + }
    +
    + cmd->data_len = length;
    + cmd->out_data_type = hw_info_type;
    + rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
    +
    +err_put:
    + iommufd_put_object(&idev->obj);
    + return rc;
    +}
    +
    static int iommufd_fops_open(struct inode *inode, struct file *filp)
    {
    struct iommufd_ctx *ictx;
    @@ -265,6 +359,7 @@ static int iommufd_option(struct iommufd_ucmd *ucmd)

    union ucmd_buffer {
    struct iommu_destroy destroy;
    + struct iommu_hw_info info;
    struct iommu_hwpt_alloc hwpt;
    struct iommu_ioas_alloc alloc;
    struct iommu_ioas_allow_iovas allow_iovas;
    @@ -297,6 +392,8 @@ struct iommufd_ioctl_op {
    }
    static const struct iommufd_ioctl_op iommufd_ioctl_ops[] = {
    IOCTL_OP(IOMMU_DESTROY, iommufd_destroy, struct iommu_destroy, id),
    + IOCTL_OP(IOMMU_GET_HW_INFO, iommufd_get_hw_info, struct iommu_hw_info,
    + __reserved),
    IOCTL_OP(IOMMU_HWPT_ALLOC, iommufd_hwpt_alloc, struct iommu_hwpt_alloc,
    __reserved),
    IOCTL_OP(IOMMU_IOAS_ALLOC, iommufd_ioas_alloc_ioctl,
    diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
    index ac11ace21edb..4a00f8fb2d54 100644
    --- a/include/uapi/linux/iommufd.h
    +++ b/include/uapi/linux/iommufd.h
    @@ -46,6 +46,7 @@ enum {
    IOMMUFD_CMD_OPTION,
    IOMMUFD_CMD_VFIO_IOAS,
    IOMMUFD_CMD_HWPT_ALLOC,
    + IOMMUFD_CMD_GET_HW_INFO,
    };

    /**
    @@ -379,4 +380,39 @@ struct iommu_hwpt_alloc {
    enum iommu_hw_info_type {
    IOMMU_HW_INFO_TYPE_NONE,
    };
    +
    +/**
    + * struct iommu_hw_info - ioctl(IOMMU_GET_HW_INFO)
    + * @size: sizeof(struct iommu_hw_info)
    + * @flags: Must be 0
    + * @dev_id: The device bound to the iommufd
    + * @data_len: Input the length of the user buffer in bytes. Output the length
    + * of data filled in the user buffer.
    + * @data_ptr: Pointer to the user buffer
    + * @out_data_type: Output the iommu hardware info type as defined in the enum
    + * iommu_hw_info_type.
    + * @__reserved: Must be 0
    + *
    + * Query the hardware information from an iommu behind a given device that has
    + * been bound to iommufd. @data_len is the size of the buffer, which captures an
    + * iommu type specific input data and a filled output data. Trailing bytes will
    + * be zeroed if the user buffer is larger than the data kernel has.
    + *
    + * The type specific data would be used to sync capabilities between the virtual
    + * IOMMU and the hardware IOMMU, e.g. a nested translation setup needs to check
    + * the hardware information, so the guest stage-1 page table will be compatible.
    + *
    + * The @out_data_type will be filled if the ioctl succeeds. It would be used to
    + * decode the data filled in the buffer pointed by @data_ptr.
    + */
    +struct iommu_hw_info {
    + __u32 size;
    + __u32 flags;
    + __u32 dev_id;
    + __u32 data_len;
    + __aligned_u64 data_ptr;
    + __u32 out_data_type;
    + __u32 __reserved;
    +};
    +#define IOMMU_GET_HW_INFO _IO(IOMMUFD_TYPE, IOMMUFD_CMD_GET_HW_INFO)
    #endif
    --
    2.34.1
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