From: Jacob Pan <jacob.pan@linux.microsoft.com>
To: linux-kernel@vger.kernel.org,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Jason Gunthorpe <jgg@nvidia.com>,
Alex Williamson <alex@shazbot.org>,
Joerg Roedel <joro@8bytes.org>,
Mostafa Saleh <smostafa@google.com>,
David Matlack <dmatlack@google.com>,
Robin Murphy <robin.murphy@arm.com>,
Nicolin Chen <nicolinc@nvidia.com>,
"Tian, Kevin" <kevin.tian@intel.com>, Yi Liu <yi.l.liu@intel.com>
Cc: Saurabh Sengar <ssengar@linux.microsoft.com>,
skhawaja@google.com, pasha.tatashin@soleen.com,
Will Deacon <will@kernel.org>,
Baolu Lu <baolu.lu@linux.intel.com>,
jacob.pan@linux.microsoft.com
Subject: Re: [PATCH v5 5/9] iommufd: Add an ioctl to query PA from IOVA for noiommu mode
Date: Mon, 11 May 2026 11:58:26 -0700 [thread overview]
Message-ID: <20260511115826.00000f6d@linux.microsoft.com> (raw)
In-Reply-To: <20260511184116.3687392-6-jacob.pan@linux.microsoft.com>
On Mon, 11 May 2026 11:41:10 -0700
Jacob Pan <jacob.pan@linux.microsoft.com> wrote:
> To support no-IOMMU mode where userspace drivers perform unsafe DMA
> using physical addresses, introduce a new API to retrieve the
> physical address of a user-allocated DMA buffer that has been mapped
> to an IOVA via IOAS. The mapping is backed by SW-only I/O page tables
> maintained by the generic IOMMUPT framework.
>
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
> ---
> v5:
> - Add header stubs for iopt_get_phys() and
> iommufd_ioas_noiommu_get_pa() to avoid ifdef at call sites
> (Kevin) v4:
> - Fix ioctl return type (Yi Liu)
This is not the correct change log, I have made a mistake. The correct
one should be:
- Fix next_iova exceeds iopt_area_last_iova (Alex)
- Rename IOCTL more specific to NOIOMMU, i.e.
IOMMUFD_CMD_IOAS_NOIOMMU_GET_PA (Kevin)
Sorry about that.
> v2:
> - New patch
> ---
> drivers/iommu/iommufd/io_pagetable.c | 62
> +++++++++++++++++++++++++ drivers/iommu/iommufd/ioas.c |
> 30 ++++++++++++ drivers/iommu/iommufd/iommufd_private.h | 18 +++++++
> drivers/iommu/iommufd/main.c | 3 ++
> include/uapi/linux/iommufd.h | 25 ++++++++++
> 5 files changed, 138 insertions(+)
>
> diff --git a/drivers/iommu/iommufd/io_pagetable.c
> b/drivers/iommu/iommufd/io_pagetable.c index
> 24d4917105d9..1ee7c8e6408c 100644 ---
> a/drivers/iommu/iommufd/io_pagetable.c +++
> b/drivers/iommu/iommufd/io_pagetable.c @@ -859,6 +859,68 @@ int
> iopt_unmap_iova(struct io_pagetable *iopt, unsigned long iova, return
> iopt_unmap_iova_range(iopt, iova, iova_last, unmapped); }
>
> +#ifdef CONFIG_IOMMUFD_NOIOMMU
> +int iopt_get_phys(struct io_pagetable *iopt, unsigned long iova, u64
> *paddr,
> + u64 *length)
> +{
> + struct iopt_area *area;
> + u64 tmp_length = 0;
> + u64 tmp_paddr = 0;
> + int rc = 0;
> +
> + down_read(&iopt->iova_rwsem);
> + area = iopt_area_iter_first(iopt, iova, iova);
> + if (!area || !area->pages) {
> + rc = -ENOENT;
> + goto unlock_exit;
> + }
> +
> + if (!area->storage_domain ||
> + area->storage_domain->owner != &iommufd_noiommu_ops) {
> + rc = -EOPNOTSUPP;
> + goto unlock_exit;
> + }
> +
> + *paddr = iommu_iova_to_phys(area->storage_domain, iova);
> + if (!*paddr) {
> + rc = -EINVAL;
> + goto unlock_exit;
> + }
> +
> + tmp_length = PAGE_SIZE - offset_in_page(iova);
> + tmp_paddr = *paddr;
> + /*
> + * Scan the domain for the contiguous physical address
> length so that
> + * userspace search can be optimized for fewer ioctls.
> + */
> + while (iova < iopt_area_last_iova(area)) {
> + unsigned long next_iova;
> + u64 next_paddr;
> +
> + if (check_add_overflow(iova, PAGE_SIZE, &next_iova))
> + break;
> +
> + if (next_iova > iopt_area_last_iova(area))
> + break;
> +
> + next_paddr =
> iommu_iova_to_phys(area->storage_domain, next_iova); +
> + if (!next_paddr || next_paddr != tmp_paddr +
> PAGE_SIZE)
> + break;
> +
> + iova = next_iova;
> + tmp_paddr += PAGE_SIZE;
> + tmp_length += PAGE_SIZE;
> + }
> + *length = tmp_length;
> +
> +unlock_exit:
> + up_read(&iopt->iova_rwsem);
> +
> + return rc;
> +}
> +#endif
> +
> int iopt_unmap_all(struct io_pagetable *iopt, unsigned long
> *unmapped) {
> /* If the IOVAs are empty then unmap all succeeds */
> diff --git a/drivers/iommu/iommufd/ioas.c
> b/drivers/iommu/iommufd/ioas.c index fed06c2b728e..666440e32c9e 100644
> --- a/drivers/iommu/iommufd/ioas.c
> +++ b/drivers/iommu/iommufd/ioas.c
> @@ -375,6 +375,36 @@ int iommufd_ioas_unmap(struct iommufd_ucmd *ucmd)
> return rc;
> }
>
> +#ifdef CONFIG_IOMMUFD_NOIOMMU
> +int iommufd_ioas_noiommu_get_pa(struct iommufd_ucmd *ucmd)
> +{
> + struct iommu_ioas_noiommu_get_pa *cmd = ucmd->cmd;
> + struct iommufd_ioas *ioas;
> + int rc;
> +
> + if (!capable(CAP_SYS_RAWIO))
> + return -EPERM;
> +
> + if (cmd->flags || cmd->__reserved)
> + return -EOPNOTSUPP;
> +
> + ioas = iommufd_get_ioas(ucmd->ictx, cmd->ioas_id);
> + if (IS_ERR(ioas))
> + return PTR_ERR(ioas);
> +
> + rc = iopt_get_phys(&ioas->iopt, cmd->iova, &cmd->out_phys,
> + &cmd->out_length);
> + if (rc)
> + goto out_put;
> +
> + rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
> +out_put:
> + iommufd_put_object(ucmd->ictx, &ioas->obj);
> +
> + return rc;
> +}
> +#endif
> +
> static void iommufd_release_all_iova_rwsem(struct iommufd_ctx *ictx,
> struct xarray *ioas_list)
> {
> diff --git a/drivers/iommu/iommufd/iommufd_private.h
> b/drivers/iommu/iommufd/iommufd_private.h index
> 2682b5baa6e9..13f1506d8066 100644 ---
> a/drivers/iommu/iommufd/iommufd_private.h +++
> b/drivers/iommu/iommufd/iommufd_private.h @@ -118,6 +118,16 @@ int
> iopt_map_pages(struct io_pagetable *iopt, struct list_head
> *pages_list, int iopt_unmap_iova(struct io_pagetable *iopt, unsigned
> long iova, unsigned long length, unsigned long *unmapped); int
> iopt_unmap_all(struct io_pagetable *iopt, unsigned long *unmapped);
> +#ifdef CONFIG_IOMMUFD_NOIOMMU +int iopt_get_phys(struct io_pagetable
> *iopt, unsigned long iova, u64 *paddr,
> + u64 *length);
> +#else
> +static inline int iopt_get_phys(struct io_pagetable *iopt, unsigned
> long iova,
> + u64 *paddr, u64 *length)
> +{
> + return -EOPNOTSUPP;
> +}
> +#endif
>
> int iopt_read_and_clear_dirty_data(struct io_pagetable *iopt,
> struct iommu_domain *domain,
> @@ -346,6 +356,14 @@ int iommufd_ioas_map_file(struct iommufd_ucmd
> *ucmd); int iommufd_ioas_change_process(struct iommufd_ucmd *ucmd);
> int iommufd_ioas_copy(struct iommufd_ucmd *ucmd);
> int iommufd_ioas_unmap(struct iommufd_ucmd *ucmd);
> +#ifdef CONFIG_IOMMUFD_NOIOMMU
> +int iommufd_ioas_noiommu_get_pa(struct iommufd_ucmd *ucmd);
> +#else
> +static inline int iommufd_ioas_noiommu_get_pa(struct iommufd_ucmd
> *ucmd) +{
> + return -EOPNOTSUPP;
> +}
> +#endif
> int iommufd_ioas_option(struct iommufd_ucmd *ucmd);
> int iommufd_option_rlimit_mode(struct iommu_option *cmd,
> struct iommufd_ctx *ictx);
> diff --git a/drivers/iommu/iommufd/main.c
> b/drivers/iommu/iommufd/main.c index 8c6d43601afb..3b4192d70570 100644
> --- a/drivers/iommu/iommufd/main.c
> +++ b/drivers/iommu/iommufd/main.c
> @@ -424,6 +424,7 @@ union ucmd_buffer {
> struct iommu_ioas_alloc alloc;
> struct iommu_ioas_allow_iovas allow_iovas;
> struct iommu_ioas_copy ioas_copy;
> + struct iommu_ioas_noiommu_get_pa noiommu_get_pa;
> struct iommu_ioas_iova_ranges iova_ranges;
> struct iommu_ioas_map map;
> struct iommu_ioas_unmap unmap;
> @@ -482,6 +483,8 @@ static const struct iommufd_ioctl_op
> iommufd_ioctl_ops[] = { IOCTL_OP(IOMMU_IOAS_MAP, iommufd_ioas_map,
> struct iommu_ioas_map, iova), IOCTL_OP(IOMMU_IOAS_MAP_FILE,
> iommufd_ioas_map_file, struct iommu_ioas_map_file, iova),
> + IOCTL_OP(IOMMU_IOAS_NOIOMMU_GET_PA,
> iommufd_ioas_noiommu_get_pa, struct iommu_ioas_noiommu_get_pa,
> + out_phys),
> IOCTL_OP(IOMMU_IOAS_UNMAP, iommufd_ioas_unmap, struct
> iommu_ioas_unmap, length),
> IOCTL_OP(IOMMU_OPTION, iommufd_option, struct iommu_option,
> val64), diff --git a/include/uapi/linux/iommufd.h
> b/include/uapi/linux/iommufd.h index e998dfbd6960..7df366d161f1 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -57,6 +57,7 @@ enum {
> IOMMUFD_CMD_IOAS_CHANGE_PROCESS = 0x92,
> IOMMUFD_CMD_VEVENTQ_ALLOC = 0x93,
> IOMMUFD_CMD_HW_QUEUE_ALLOC = 0x94,
> + IOMMUFD_CMD_IOAS_NOIOMMU_GET_PA = 0x95,
> };
>
> /**
> @@ -219,6 +220,30 @@ struct iommu_ioas_map {
> };
> #define IOMMU_IOAS_MAP _IO(IOMMUFD_TYPE, IOMMUFD_CMD_IOAS_MAP)
>
> +/**
> + * struct iommu_ioas_noiommu_get_pa -
> ioctl(IOMMU_IOAS_NOIOMMU_GET_PA)
> + * @size: sizeof(struct iommu_ioas_noiommu_get_pa)
> + * @flags: Reserved, must be 0 for now
> + * @ioas_id: IOAS ID to query IOVA to PA mapping from
> + * @__reserved: Must be 0
> + * @iova: IOVA to query
> + * @out_length: Number of bytes contiguous physical address starting
> from phys
> + * @out_phys: Output physical address the IOVA maps to
> + *
> + * Query the physical address backing an IOVA range. The entire
> range must be
> + * mapped already. For noiommu devices doing unsafe DMA only.
> + */
> +struct iommu_ioas_noiommu_get_pa {
> + __u32 size;
> + __u32 flags;
> + __u32 ioas_id;
> + __u32 __reserved;
> + __aligned_u64 iova;
> + __aligned_u64 out_length;
> + __aligned_u64 out_phys;
> +};
> +#define IOMMU_IOAS_NOIOMMU_GET_PA _IO(IOMMUFD_TYPE,
> IOMMUFD_CMD_IOAS_NOIOMMU_GET_PA) +
> /**
> * struct iommu_ioas_map_file - ioctl(IOMMU_IOAS_MAP_FILE)
> * @size: sizeof(struct iommu_ioas_map_file)
next prev parent reply other threads:[~2026-05-11 18:58 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-11 18:41 [PATCH v5 0/9] iommufd: Enable noiommu mode for cdev Jacob Pan
2026-05-11 18:41 ` [PATCH v5 1/9] vfio: Rename VFIO_NOIOMMU to VFIO_GROUP_NOIOMMU Jacob Pan
2026-05-11 18:41 ` [PATCH v5 2/9] iommufd: Support a HWPT without an iommu driver for noiommu Jacob Pan
2026-05-11 18:41 ` [PATCH v5 3/9] iommufd: Move igroup allocation to a function Jacob Pan
2026-05-11 18:41 ` [PATCH v5 4/9] iommufd: Allow binding to a noiommu device Jacob Pan
2026-05-11 18:41 ` [PATCH v5 5/9] iommufd: Add an ioctl to query PA from IOVA for noiommu mode Jacob Pan
2026-05-11 18:58 ` Jacob Pan [this message]
2026-05-11 18:41 ` [PATCH v5 6/9] vfio/group: Add VFIO_CDEV_NOIOMMU Kconfig and tolerate NULL group Jacob Pan
2026-05-11 18:41 ` [PATCH v5 7/9] vfio: Enable cdev noiommu mode under iommufd Jacob Pan
2026-05-11 18:41 ` [PATCH v5 8/9] selftests/vfio: Add iommufd noiommu mode selftest for cdev Jacob Pan
2026-05-11 18:41 ` [PATCH v5 9/9] Documentation: Update VFIO NOIOMMU mode Jacob Pan
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