The AMD vIOMMU virtualizes guest MMIO registers at the 3rd 4K region.
This is achieved using the iommufd_viommu_alloc_mmap().

Co-developed-by: Vasant Hegde <Vasant.Hegde@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 drivers/iommu/amd/amd_viommu.h |  5 +++++
 drivers/iommu/amd/iommufd.c    | 17 ++++++++++++++++-
 drivers/iommu/amd/viommu.c     | 11 +++++++++++
 include/uapi/linux/iommufd.h   |  2 ++
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/amd_viommu.h b/drivers/iommu/amd/amd_viommu.h
index 45c2b71af4ba..8dbb12241e8d 100644
--- a/drivers/iommu/amd/amd_viommu.h
+++ b/drivers/iommu/amd/amd_viommu.h
@@ -10,6 +10,7 @@
 
 int amd_viommu_init(struct amd_iommu *iommu);
 
+u64 amd_viommu_get_vfmmio_addr(struct amd_iommu *iommu, u16 gid);
 #else
 
 static inline int amd_viommu_init(struct amd_iommu *iommu)
@@ -17,6 +18,10 @@ static inline int amd_viommu_init(struct amd_iommu *iommu)
 	return 0;
 }
 
+u64 amd_viommu_get_vfmmio_addr(struct amd_iommu *iommu, u16 gid);
+{
+	return 0;
+}
 #endif /* CONFIG_AMD_IOMMU_IOMMUFD */
 
 #endif /* AMD_VIOMMU_H */
diff --git a/drivers/iommu/amd/iommufd.c b/drivers/iommu/amd/iommufd.c
index 6fba5d9b1310..5dcd3fc3ba99 100644
--- a/drivers/iommu/amd/iommufd.c
+++ b/drivers/iommu/amd/iommufd.c
@@ -7,6 +7,7 @@
 
 #include "iommufd.h"
 #include "amd_iommu.h"
+#include "amd_viommu.h"
 #include "amd_iommu_types.h"
 
 static const struct iommufd_viommu_ops amd_viommu_ops;
@@ -44,9 +45,11 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 			    const struct iommu_user_data *user_data)
 {
 	int ret;
+	phys_addr_t page_base;
 	unsigned long flags;
 	struct iommu_viommu_amd data;
 	struct protection_domain *pdom = to_pdomain(parent);
+	struct amd_iommu *iommu = container_of(viommu->iommu_dev, struct amd_iommu, iommu);
 	struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
 
 	xa_init_flags(&aviommu->gdomid_array, XA_FLAGS_ALLOC1);
@@ -66,11 +69,21 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 		return aviommu->gid;
 	pr_debug("%s: gid=%#x", __func__, aviommu->gid);
 
+	page_base = amd_viommu_get_vfmmio_addr(iommu, aviommu->gid);
+	if (page_base <= 0)
+		return -ENODEV;
+
+	ret = iommufd_viommu_alloc_mmap(&aviommu->core,
+					page_base, SZ_4K,
+					(unsigned long *)&data.out_vfmmio_mmap_offset);
+	if (ret)
+		goto err_out;
+
 	ret = iommu_copy_struct_to_user(user_data, &data,
 					IOMMU_VIOMMU_TYPE_AMD,
 					reserved);
 	if (ret)
-		goto err_out;
+		goto free_mmap;
 
 	viommu->ops = &amd_viommu_ops;
 
@@ -79,6 +92,8 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 	spin_unlock_irqrestore(&pdom->lock, flags);
 
 	return 0;
+free_mmap:
+	iommufd_viommu_destroy_mmap(&aviommu->core, data.out_vfmmio_mmap_offset);
 err_out:
 	amd_iommu_gid_free(aviommu->gid);
 	return ret;
diff --git a/drivers/iommu/amd/viommu.c b/drivers/iommu/amd/viommu.c
index 887a9eb8122d..76198bf4f4f6 100644
--- a/drivers/iommu/amd/viommu.c
+++ b/drivers/iommu/amd/viommu.c
@@ -92,6 +92,17 @@ static int __init viommu_vf_vfcntl_init(struct amd_iommu *iommu)
 	return 0;
 }
 
+/*
+ * Returns VF MMIO BAR offset for the give guest ID which will be
+ * mapped to guest vIOMMU 3rd 4K MMIO address
+ */
+u64 amd_viommu_get_vfmmio_addr(struct amd_iommu *iommu, u16 gid)
+{
+	/* TODO: Add check for sVIOMMU and set gid[bit 15] */
+	return iommu->vf_base_phys + gid * VIOMMU_VF_MMIO_ENTRY_SIZE;
+}
+EXPORT_SYMBOL(amd_viommu_get_vfmmio_addr);
+
 int __init amd_viommu_init(struct amd_iommu *iommu)
 {
 	int ret;
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 3a2ac7234b9e..eff5fbd2da6b 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -1075,9 +1075,11 @@ struct iommu_viommu_tegra241_cmdqv {
 
 /**
  * struct iommu_viommu_amd - AMD vIOMMU Interface (IOMMU_VIOMMU_TYPE_AMD)
+ * @out_vfmmio_mmap_offset: (out) mmap offset for vIOMMU VF-MMIO
  * @reserved: Must be zero
  */
 struct iommu_viommu_amd {
+	__aligned_u64 out_vfmmio_mmap_offset;
 	__u32 reserved; /* must be last */
 };
 
-- 
2.34.1

On Mon, Mar 30, 2026 at 1:43 AM Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> wrote:
>
> diff --git a/drivers/iommu/amd/iommufd.c b/drivers/iommu/amd/iommufd.c
> index 6fba5d9b1310..5dcd3fc3ba99 100644
> --- a/drivers/iommu/amd/iommufd.c
> +++ b/drivers/iommu/amd/iommufd.c
> @@ -66,11 +69,21 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
>                 return aviommu->gid;
>         pr_debug("%s: gid=%#x", __func__, aviommu->gid);
>
> +       page_base = amd_viommu_get_vfmmio_addr(iommu, aviommu->gid);
According to the below implementation and prototype, amd_viommu_get_vfmmio_addr() won't return negative value.

> +       if (page_base <= 0)
> +               return -ENODEV;
goto err_out here as well  to avoid leaking the gid allocated above.


> +
> +       ret = iommufd_viommu_alloc_mmap(&aviommu->core,
> +                                       page_base, SZ_4K,
> +                                       (unsigned long *)&data.out_vfmmio_mmap_offset);
> +       if (ret)
> +               goto err_out;
> +
>         ret = iommu_copy_struct_to_user(user_data, &data,
>                                         IOMMU_VIOMMU_TYPE_AMD,
>                                         reserved);
>         if (ret)
> -               goto err_out;
> +               goto free_mmap;
>
>         viommu->ops = &amd_viommu_ops;
>
> @@ -79,6 +92,8 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
>         spin_unlock_irqrestore(&pdom->lock, flags);
>
>         return 0;
> +free_mmap:
> +       iommufd_viommu_destroy_mmap(&aviommu->core, data.out_vfmmio_mmap_offset);
>  err_out:
>         amd_iommu_gid_free(aviommu->gid);
>         return ret;
> diff --git a/drivers/iommu/amd/viommu.c b/drivers/iommu/amd/viommu.c

>
> +/*
> + * Returns VF MMIO BAR offset for the give guest ID which will be
> + * mapped to guest vIOMMU 3rd 4K MMIO address
> + */
> +u64 amd_viommu_get_vfmmio_addr(struct amd_iommu *iommu, u16 gid)
> +{
> +       /* TODO: Add check for sVIOMMU and set gid[bit 15] */
> +       return iommu->vf_base_phys + gid * VIOMMU_VF_MMIO_ENTRY_SIZE;
> +}
> +EXPORT_SYMBOL(amd_viommu_get_vfmmio_addr);