Re: [PATCH v6 2/6] iommufd: Add IOMMU_HWPT_INVALIDATE

[Yi Liu]

On 2023/11/20 16:09, Tian, Kevin wrote:
> > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > Sent: Friday, November 17, 2023 9:07 PM
> > +
> > +	hwpt = iommufd_hw_pagetable_get_nested(ucmd, cmd->hwpt_id);
> > +	if (IS_ERR(hwpt))
> > +		return PTR_ERR(hwpt);
> > +
> > +	rc = hwpt->domain->ops->cache_invalidate_user(hwpt->domain,
> > &data_array,
> > +						      &cmd-
> > > out_driver_error_code);
> > +	cmd->req_num = data_array.entry_num;
> > +	if (iommufd_ucmd_respond(ucmd, sizeof(*cmd)))
> > +		return -EFAULT;
> > +	iommufd_put_object(&hwpt->obj);
>
> the object is not put when ucmd response fails. It can be put right
> after calling @cache_invalidate_user()

yes.

> > @@ -309,6 +309,7 @@ union ucmd_buffer {
> >   	struct iommu_hwpt_alloc hwpt;
> >   	struct iommu_hwpt_get_dirty_bitmap get_dirty_bitmap;
> >   	struct iommu_hwpt_set_dirty_tracking set_dirty_tracking;
> > +	struct iommu_hwpt_invalidate cache;
>
> In alphabetic order this should be put before "hwpt_set_dirty"

yes.

> >   	struct iommu_ioas_alloc alloc;
> >   	struct iommu_ioas_allow_iovas allow_iovas;
> >   	struct iommu_ioas_copy ioas_copy;
> > @@ -348,6 +349,8 @@ static const struct iommufd_ioctl_op
> > iommufd_ioctl_ops[] = {
> >   		 struct iommu_hwpt_get_dirty_bitmap, data),
> >   	IOCTL_OP(IOMMU_HWPT_SET_DIRTY_TRACKING,
> > iommufd_hwpt_set_dirty_tracking,
> >   		 struct iommu_hwpt_set_dirty_tracking, __reserved),
> > +	IOCTL_OP(IOMMU_HWPT_INVALIDATE, iommufd_hwpt_invalidate,
> > +		 struct iommu_hwpt_invalidate, out_driver_error_code),
>
> ditto
>
> > +/**
> > + * struct iommu_hwpt_invalidate - ioctl(IOMMU_HWPT_INVALIDATE)
> > + * @size: sizeof(struct iommu_hwpt_invalidate)
> > + * @hwpt_id: HWPT ID of a nested HWPT for cache invalidation
>
> remove the first 'HWPT'

> > + * @reqs_uptr: User pointer to an array having @req_num of cache
> > invalidation
> > + *             requests. The request entries in the array are of fixed width
> > + *             @req_len, and contain a user data structure for invalidation
> > + *             request specific to the given hardware page table.
> > + * @req_type: One of enum iommu_hwpt_data_type, defining the data
> > type of all
> > + *            the entries in the invalidation request array. It should suit
> > + *            with the data_type passed per the allocation of the hwpt pointed
> > + *            by @hwpt_id.
>
> "It should match the data_type given to the specified hwpt"

above comments are well received. :)

> > + * @req_len: Length (in bytes) of a request entry in the request array
> > + * @req_num: Input the number of cache invalidation requests in the array.
> > + *           Output the number of requests successfully handled by kernel.
> > + * @out_driver_error_code: Report a driver speicifc error code upon failure.
> > + *                         It's optional, driver has a choice to fill it or
> > + *                         not.
>
> Being optional how does the user tell whether the code is filled or not?

seems like we need a flag for it. otherwise, a reserved special value is
required. or is it enough to just document it that this field is available
or not per the iommu_hw_info_type?

> > + *
> > + * Invalidate the iommu cache for user-managed page table. Modifications
> > on a
> > + * user-managed page table should be followed by this operation to sync
> > cache.
> > + * Each ioctl can support one or more cache invalidation requests in the
> > array
> > + * that has a total size of @req_len * @req_num.
> > + */
> > +struct iommu_hwpt_invalidate {
> > +	__u32 size;
> > +	__u32 hwpt_id;
> > +	__aligned_u64 reqs_uptr;
> > +	__u32 req_type;
> > +	__u32 req_len;
> > +	__u32 req_num;
> > +	__u32 out_driver_error_code;
> > +};
>
> Probably 'data_uptr', 'data_type', "entry_len' and 'entry_num" read slightly
> better.

sure.

--
Regards,
Yi Liu