RE: [PATCH 07/12] iommufd: Add IOMMU_HWPT_INVALIDATE

[Liu, Yi L]

> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Friday, March 10, 2023 11:16 AM
> 
> On 3/9/23 4:09 PM, Yi Liu wrote:
> > In nested translation, the stage-1 page table is user-managed and used
> > by IOMMU hardware, so destroying mappings in the stage-1 page table
> should
> > be followed with an IOTLB invalidation.
> 
> s/destroying mappings/update of any present page table entry/

Right. Not only destroying.

> > This adds IOMMU_HWPT_INVALIDATE for IOTLB invalidation.
> >
> > 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/hw_pagetable.c    | 56
> +++++++++++++++++++++++++
> >   drivers/iommu/iommufd/iommufd_private.h |  9 ++++
> >   drivers/iommu/iommufd/main.c            |  3 ++
> >   include/uapi/linux/iommufd.h            | 27 ++++++++++++
> >   4 files changed, 95 insertions(+)
> >
> > diff --git a/drivers/iommu/iommufd/hw_pagetable.c
> b/drivers/iommu/iommufd/hw_pagetable.c
> > index 64e7cf7142e1..67facca98de1 100644
> > --- a/drivers/iommu/iommufd/hw_pagetable.c
> > +++ b/drivers/iommu/iommufd/hw_pagetable.c
> > @@ -284,3 +284,59 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd
> *ucmd)
> >   	iommufd_put_object(&idev->obj);
> >   	return rc;
> >   }
> > +
> > +/*
> > + * size of page table type specific invalidate_info, indexed by
> > + * enum iommu_hwpt_type.
> > + */
> > +static const size_t iommufd_hwpt_invalidate_info_size[] = {};
> > +
> > +int iommufd_hwpt_invalidate(struct iommufd_ucmd *ucmd)
> > +{
> > +	struct iommu_hwpt_invalidate *cmd = ucmd->cmd;
> > +	struct iommufd_hw_pagetable *hwpt;
> > +	u64 user_ptr;
> > +	u32 user_data_len, klen;
> > +	int rc = 0;
> > +
> > +	/*
> > +	 * For a user-managed HWPT, type should not be
> IOMMU_HWPT_TYPE_DEFAULT.
> > +	 * data_len should not exceed the size of
> iommufd_invalidate_buffer.
> > +	 */
> > +	if (cmd->data_type == IOMMU_HWPT_TYPE_DEFAULT || !cmd-
> >data_len ||
> > +	    cmd->data_type >=
> ARRAY_SIZE(iommufd_hwpt_invalidate_info_size))
> 
> "data_len should not exceed the size of iommufd_invalidate_buffer."
> 
> How is this checked?

Hmmm, this is a stale comment I suppose.

> 
> > +		return -EOPNOTSUPP;
> > +
> > +	hwpt = iommufd_get_hwpt(ucmd, cmd->hwpt_id);
> > +	if (IS_ERR(hwpt))
> > +		return PTR_ERR(hwpt);
> > +
> > +	/* Do not allow any kernel-managed hw_pagetable */
> > +	if (!hwpt->parent) {
> > +		rc = -EINVAL;
> > +		goto out_put_hwpt;
> > +	}
> > +
> > +	klen = iommufd_hwpt_invalidate_info_size[cmd->data_type];
> > +	if (!klen) {
> > +		rc = -EINVAL;
> > +		goto out_put_hwpt;
> > +	}
> > +
> > +	/*
> > +	 * Copy the needed fields before reusing the ucmd buffer, this
> > +	 * avoids memory allocation in this path.
> > +	 */
> > +	user_ptr = cmd->data_uptr;
> > +	user_data_len = cmd->data_len;
> 
> Is it a valid case if "user_data_len < klen"?

Yes. e.g. an old qemu running on a new kernel which has new field
added in the end of the data structure.

Regards,
Yi Liu