diff mbox series

[v6,3/4] iommufd: Add IOMMU_GET_HW_INFO

Message ID 20230808153510.4170-4-yi.l.liu@intel.com (mailing list archive)
State New, archived
Headers show
Series iommufd: Add iommu hardware info reporting | expand

Commit Message

Yi Liu Aug. 8, 2023, 3:35 p.m. UTC 
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(+)

Comments

Baolu Lu Aug. 9, 2023, 10:16 a.m. UTC | #1 
On 2023/8/8 23:35, Yi Liu wrote:
> +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)) {

copy_to_user() returns the number of bytes that were successfully
copied, right?

If so, isn't it always failure case? Or I missed anything?

> +		rc = -EFAULT;
> +		goto err_free;

nit: this goto is unnecessary.

> +	}
> +
> +err_free:
> +	kfree(data);
> +	return rc;
> +}

Best regards,
baolu
Jason Gunthorpe Aug. 9, 2023, 4:16 p.m. UTC | #2 
On Wed, Aug 09, 2023 at 06:16:19PM +0800, Baolu Lu wrote:
> On 2023/8/8 23:35, Yi Liu wrote:
> > +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)) {
> 
> copy_to_user() returns the number of bytes that were successfully
> copied, right?

It returns length on failure and 0 on success

Jason
Jason Gunthorpe Aug. 9, 2023, 4:43 p.m. UTC | #3 
On Tue, Aug 08, 2023 at 08:35:09AM -0700, Yi Liu wrote:
> +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;
> +	}

I've recently learned this routine is spelled 'clear_user()'

Jason
Baolu Lu Aug. 10, 2023, 2:05 a.m. UTC | #4 
On 2023/8/10 0:16, Jason Gunthorpe wrote:
> On Wed, Aug 09, 2023 at 06:16:19PM +0800, Baolu Lu wrote:
>> On 2023/8/8 23:35, Yi Liu wrote:
>>> +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)) {
>> copy_to_user() returns the number of bytes that were successfully
>> copied, right?
> It returns length on failure and 0 on success

Then it's fine. Thanks for the explanation.

Best regards,
baolu
Yi Liu Aug. 10, 2023, 3:35 a.m. UTC | #5 
> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Thursday, August 10, 2023 12:44 AM
> 
> On Tue, Aug 08, 2023 at 08:35:09AM -0700, Yi Liu wrote:
> > +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;
> > +	}
> 
> I've recently learned this routine is spelled 'clear_user()'

I see. Will replace with it.

Regards,
Yi Liu
diff mbox series

Patch

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