Re: [PATCH v2 08/22] iommufd: Abstract iopt_pin_pages and iopt_unpin_pages helpers

Pranjal Shrivastava
2025-04-28T20:16:51Z

On Fri, Apr 25, 2025 at 10:58:03PM -0700, Nicolin Chen wrote:
> The new vCMDQ object will be added for HW to access the guest memory for a
> HW-accelerated virtualization feature. It needs to ensure the guest memory
> pages are pinned when HW accesses them and they are contiguous in physical
> address space.
>
> This is very like the existing iommufd_access_pin_pages() that outputs the
> pinned page list for the caller to test its contiguity.
>
> Move those code from iommufd_access_pin/unpin_pages() and related function
> for a pair of iopt helpers that can be shared with the vCMDQ allocator. As
> the vCMDQ allocator will be a user-space triggered ioctl function, WARN_ON
> would not be a good fit in the new iopt_unpin_pages(), thus change them to
> use WARN_ON_ONCE instead.
>
> Rename check_area_prot() to align with the existing iopt_area helpers, and
> inline it to the header since iommufd_access_rw() still uses it.
>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
> drivers/iommu/iommufd/io_pagetable.h | 8 ++
> drivers/iommu/iommufd/iommufd_private.h | 6 ++
> drivers/iommu/iommufd/device.c | 117 ++----------------------
> drivers/iommu/iommufd/io_pagetable.c | 95 +++++++++++++++++++
> 4 files changed, 117 insertions(+), 109 deletions(-)
>
> diff --git a/drivers/iommu/iommufd/io_pagetable.h b/drivers/iommu/iommufd/io_pagetable.h
> index 10c928a9a463..4288a2b1a90f 100644
> --- a/drivers/iommu/iommufd/io_pagetable.h
> +++ b/drivers/iommu/iommufd/io_pagetable.h
> @@ -114,6 +114,14 @@ static inline unsigned long iopt_area_iova_to_index(struct iopt_area *area,
> return iopt_area_start_byte(area, iova) / PAGE_SIZE;
> }
>
> +static inline bool iopt_area_check_prot(struct iopt_area *area,
> + unsigned int flags)
> +{
> + if (flags & IOMMUFD_ACCESS_RW_WRITE)
> + return area->iommu_prot & IOMMU_WRITE;
> + return area->iommu_prot & IOMMU_READ;
> +}
> +
> #define __make_iopt_iter(name) \
> static inline struct iopt_##name *iopt_##name##_iter_first( \
> struct io_pagetable *iopt, unsigned long start, \
> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> index 8d96aa514033..79160b039bc7 100644
> --- a/drivers/iommu/iommufd/iommufd_private.h
> +++ b/drivers/iommu/iommufd/iommufd_private.h
> @@ -130,6 +130,12 @@ int iopt_cut_iova(struct io_pagetable *iopt, unsigned long *iovas,
> void iopt_enable_large_pages(struct io_pagetable *iopt);
> int iopt_disable_large_pages(struct io_pagetable *iopt);
>
> +int iopt_pin_pages(struct io_pagetable *iopt, unsigned long iova,
> + unsigned long length, struct page **out_pages,
> + unsigned int flags);
> +void iopt_unpin_pages(struct io_pagetable *iopt, unsigned long iova,
> + unsigned long length);
> +
> struct iommufd_ucmd {
> struct iommufd_ctx *ictx;
> void __user *ubuffer;
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 2111bad72c72..a5c6be164254 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -1240,58 +1240,17 @@ void iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long iova,
> void iommufd_access_unpin_pages(struct iommufd_access *access,
> unsigned long iova, unsigned long length)
> {
> - struct iopt_area_contig_iter iter;
> - struct io_pagetable *iopt;
> - unsigned long last_iova;
> - struct iopt_area *area;
> -
> - if (WARN_ON(!length) ||
> - WARN_ON(check_add_overflow(iova, length - 1, &last_iova)))
> - return;
> -
> - mutex_lock(&access->ioas_lock);
> + guard(mutex)(&access->ioas_lock);
> /*
> * The driver must be doing something wrong if it calls this before an
> * iommufd_access_attach() or after an iommufd_access_detach().
> */
> - if (WARN_ON(!access->ioas_unpin)) {
> - mutex_unlock(&access->ioas_lock);
> + if (WARN_ON(!access->ioas_unpin))
> return;
> - }
> - iopt = &access->ioas_unpin->iopt;
> -
> - down_read(&iopt->iova_rwsem);
> - iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
> - iopt_area_remove_access(
> - area, iopt_area_iova_to_index(area, iter.cur_iova),
> - iopt_area_iova_to_index(
> - area,
> - min(last_iova, iopt_area_last_iova(area))));
> - WARN_ON(!iopt_area_contig_done(&iter));
> - up_read(&iopt->iova_rwsem);
> - mutex_unlock(&access->ioas_lock);
> + iopt_unpin_pages(&access->ioas_unpin->iopt, iova, length);
> }
> EXPORT_SYMBOL_NS_GPL(iommufd_access_unpin_pages, "IOMMUFD");
>
> -static bool iopt_area_contig_is_aligned(struct iopt_area_contig_iter *iter)
> -{
> - if (iopt_area_start_byte(iter->area, iter->cur_iova) % PAGE_SIZE)
> - return false;
> -
> - if (!iopt_area_contig_done(iter) &&
> - (iopt_area_start_byte(iter->area, iopt_area_last_iova(iter->area)) %
> - PAGE_SIZE) != (PAGE_SIZE - 1))
> - return false;
> - return true;
> -}
> -
> -static bool check_area_prot(struct iopt_area *area, unsigned int flags)
> -{
> - if (flags & IOMMUFD_ACCESS_RW_WRITE)
> - return area->iommu_prot & IOMMU_WRITE;
> - return area->iommu_prot & IOMMU_READ;
> -}
> -
> /**
> * iommufd_access_pin_pages() - Return a list of pages under the iova
> * @access: IOAS access to act on
> @@ -1315,76 +1274,16 @@ int iommufd_access_pin_pages(struct iommufd_access *access, unsigned long iova,
> unsigned long length, struct page **out_pages,
> unsigned int flags)
> {
> - struct iopt_area_contig_iter iter;
> - struct io_pagetable *iopt;
> - unsigned long last_iova;
> - struct iopt_area *area;
> - int rc;
> -
> /* Driver's ops don't support pin_pages */
> if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
> WARN_ON(access->iova_alignment != PAGE_SIZE || !access->ops->unmap))
> return -EINVAL;
>
> - if (!length)
> - return -EINVAL;
> - if (check_add_overflow(iova, length - 1, &last_iova))
> - return -EOVERFLOW;
> -
> - mutex_lock(&access->ioas_lock);
> - if (!access->ioas) {
> - mutex_unlock(&access->ioas_lock);
> + guard(mutex)(&access->ioas_lock);
> + if (!access->ioas)
> return -ENOENT;
> - }
> - iopt = &access->ioas->iopt;
> -
> - down_read(&iopt->iova_rwsem);
> - iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
> - unsigned long last = min(last_iova, iopt_area_last_iova(area));
> - unsigned long last_index = iopt_area_iova_to_index(area, last);
> - unsigned long index =
> - iopt_area_iova_to_index(area, iter.cur_iova);
> -
> - if (area->prevent_access ||
> - !iopt_area_contig_is_aligned(&iter)) {
> - rc = -EINVAL;
> - goto err_remove;
> - }
> -
> - if (!check_area_prot(area, flags)) {
> - rc = -EPERM;
> - goto err_remove;
> - }
> -
> - rc = iopt_area_add_access(area, index, last_index, out_pages,
> - flags);
> - if (rc)
> - goto err_remove;
> - out_pages += last_index - index + 1;
> - }
> - if (!iopt_area_contig_done(&iter)) {
> - rc = -ENOENT;
> - goto err_remove;
> - }
> -
> - up_read(&iopt->iova_rwsem);
> - mutex_unlock(&access->ioas_lock);
> - return 0;
> -
> -err_remove:
> - if (iova < iter.cur_iova) {
> - last_iova = iter.cur_iova - 1;
> - iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
> - iopt_area_remove_access(
> - area,
> - iopt_area_iova_to_index(area, iter.cur_iova),
> - iopt_area_iova_to_index(
> - area, min(last_iova,
> - iopt_area_last_iova(area))));
> - }
> - up_read(&iopt->iova_rwsem);
> - mutex_unlock(&access->ioas_lock);
> - return rc;
> + return iopt_pin_pages(&access->ioas->iopt, iova, length, out_pages,
> + flags);
> }
> EXPORT_SYMBOL_NS_GPL(iommufd_access_pin_pages, "IOMMUFD");
>
> @@ -1431,7 +1330,7 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
> goto err_out;
> }
>
> - if (!check_area_prot(area, flags)) {
> + if (!iopt_area_check_prot(area, flags)) {
> rc = -EPERM;
> goto err_out;
> }
> diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
> index 8a790e597e12..160eec49af1b 100644
> --- a/drivers/iommu/iommufd/io_pagetable.c
> +++ b/drivers/iommu/iommufd/io_pagetable.c
> @@ -1472,3 +1472,98 @@ int iopt_table_enforce_dev_resv_regions(struct io_pagetable *iopt,
> up_write(&iopt->iova_rwsem);
> return rc;
> }
> +
> +static bool iopt_area_contig_is_aligned(struct iopt_area_contig_iter *iter)
> +{
> + if (iopt_area_start_byte(iter->area, iter->cur_iova) % PAGE_SIZE)
> + return false;
> +
> + if (!iopt_area_contig_done(iter) &&
> + (iopt_area_start_byte(iter->area, iopt_area_last_iova(iter->area)) %
> + PAGE_SIZE) != (PAGE_SIZE - 1))
> + return false;
> + return true;
> +}
> +
> +int iopt_pin_pages(struct io_pagetable *iopt, unsigned long iova,
> + unsigned long length, struct page **out_pages,
> + unsigned int flags)
> +{
> + struct iopt_area_contig_iter iter;
> + unsigned long last_iova;
> + struct iopt_area *area;
> + int rc;
> +
> + if (!length)
> + return -EINVAL;
> + if (check_add_overflow(iova, length - 1, &last_iova))
> + return -EOVERFLOW;
> +
> + down_read(&iopt->iova_rwsem);
> + iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova) {
> + unsigned long last = min(last_iova, iopt_area_last_iova(area));
> + unsigned long last_index = iopt_area_iova_to_index(area, last);
> + unsigned long index =
> + iopt_area_iova_to_index(area, iter.cur_iova);
> +
> + if (area->prevent_access ||

Nit:
Shouldn't we return -EBUSY or something if (area->prevent_access == 1) ?
IIUC, this just means that an unmap attempt is in progress, hence avoid
accessing the area.

> + !iopt_area_contig_is_aligned(&iter)) {
> + rc = -EINVAL;
> + goto err_remove;
> + }
> +
> + if (!iopt_area_check_prot(area, flags)) {
> + rc = -EPERM;
> + goto err_remove;
> + }
> +
> + rc = iopt_area_add_access(area, index, last_index, out_pages,
> + flags);
> + if (rc)
> + goto err_remove;
> + out_pages += last_index - index + 1;
> + }
> + if (!iopt_area_contig_done(&iter)) {
> + rc = -ENOENT;
> + goto err_remove;
> + }
> +
> + up_read(&iopt->iova_rwsem);
> + return 0;
> +
> +err_remove:
> + if (iova < iter.cur_iova) {
> + last_iova = iter.cur_iova - 1;
> + iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
> + iopt_area_remove_access(
> + area,
> + iopt_area_iova_to_index(area, iter.cur_iova),
> + iopt_area_iova_to_index(
> + area, min(last_iova,
> + iopt_area_last_iova(area))));
> + }
> + up_read(&iopt->iova_rwsem);
> + return rc;
> +}
> +
> +void iopt_unpin_pages(struct io_pagetable *iopt, unsigned long iova,
> + unsigned long length)
> +{
> + struct iopt_area_contig_iter iter;
> + unsigned long last_iova;
> + struct iopt_area *area;
> +
> + if (WARN_ON_ONCE(!length) ||
> + WARN_ON_ONCE(check_add_overflow(iova, length - 1, &last_iova)))
> + return;
> +
> + down_read(&iopt->iova_rwsem);
> + iopt_for_each_contig_area(&iter, area, iopt, iova, last_iova)
> + iopt_area_remove_access(
> + area, iopt_area_iova_to_index(area, iter.cur_iova),
> + iopt_area_iova_to_index(
> + area,
> + min(last_iova, iopt_area_last_iova(area))));
> + WARN_ON_ONCE(!iopt_area_contig_done(&iter));
> + up_read(&iopt->iova_rwsem);
> +}
> --
> 2.43.0
>