> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, August 4, 2023 9:59 AM
>
> On 2023/8/3 22:31, Yi Liu wrote:
> > 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 compatiable with the underlying IOMMU hardware. Hence,
>
> compatible
Yes.
> > 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.
> >
> > Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> > ---
> > drivers/iommu/iommufd/main.c | 79 ++++++++++++++++++++++++++++++++++++
> > include/uapi/linux/iommufd.h | 36 ++++++++++++++++
> > 2 files changed, 115 insertions(+)
> >
> > diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
> > index 94c498b8fdf6..a0302bcaa97c 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 +178,81 @@ 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_get_hw_info(struct iommufd_ucmd *ucmd)
> > +{
> > + u32 hw_info_type = IOMMU_HW_INFO_TYPE_NONE;
> > + struct iommu_hw_info *cmd = ucmd->cmd;
> > + unsigned int length = 0, data_len;
> > + struct iommufd_device *idev;
> > + const struct iommu_ops *ops;
> > + void __user *user_ptr;
> > + void *data = NULL;
> > + 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);
> > +
> > + ops = dev_iommu_ops(idev->dev);
> > + if (!ops->hw_info)
> > + goto done;
> > +
> > + data = ops->hw_info(idev->dev, &data_len, &hw_info_type);
> > + if (IS_ERR(data)) {
> > + rc = PTR_ERR(data);
> > + goto out_err;
>
> Can kfree() handle a ERR_PTR input? I am afraid not,
>
> /**
> * kfree - free previously allocated memory
> * @object: pointer returned by kmalloc() or kmem_cache_alloc()
> *
> * If @object is NULL, no operation is performed.
> */
> void kfree(const void *object)
> {
> struct folio *folio;
> struct slab *slab;
> struct kmem_cache *s;
>
> trace_kfree(_RET_IP_, object);
>
> if (unlikely(ZERO_OR_NULL_PTR(object)))
> return;
>
> So, perhaps we should add
>
> data = NULL;
>
> before
> goto out_err;
>
> ?
Yes.
>
> > + }
> > +
> > + /* driver has hw_info callback should have a unique hw_info_type */
> > + if (WARN_ON_ONCE(hw_info_type == IOMMU_HW_INFO_TYPE_NONE)) {
> > + rc = -ENODEV;
> > + goto out_err;
> > + }
> > +
> > + length = min(cmd->data_len, data_len);
> > + if (copy_to_user(user_ptr, data, length)) {
> > + rc = -EFAULT;
> > + goto out_err;
> > + }
> > +
> > +done:
> > + /*
> > + * 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 out_err;
> > + }
> > +
> > + cmd->data_len = length;
> > + cmd->out_data_type = hw_info_type;
> > + rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
> > +
> > +out_err:
> > + kfree(data);
> > + iommufd_put_object(&idev->obj);
> > + return rc;
> > +}
> > +
>
> Others look good to me, feel free to add:
>
> Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
>
> after above are addressed.
Regards,
Yi Liu
