[PATCH v5 05/24] iommu/amd: Allocate Guest IDs for IOMMUFD vIOMMU instances
From: Suravee Suthikulpanit
Date: Mon Sep 14 2026 - 14:49:27 EST
Hardware vIOMMU uses a 16-bit Guest ID (GID) per guest IOMMU to
index driver and hardware state. Allocate one GID per IOMMUFD vIOMMU
from a per-amd_iommu IDA (unique within that IOMMU; a VM behind
multiple IOMMUs may hold more than one GID).
Add amd_iommu_gid_alloc() and amd_iommu_gid_free(), store the ID in
amd_iommu_viommu::gid, and call them from amd_iommufd_viommu_init()
and destroy. Initialize gid_ida in init_iommu_one() and destroy it
in free_iommu_one() with the IOMMU object.
Reject amd_iommufd_viommu_init() with -EOPNOTSUPP when the IOMMU
does not have AMD_IOMMU_FLAG_VIOMMU_EN.
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
drivers/iommu/amd/amd_iommu.h | 4 ++++
drivers/iommu/amd/amd_iommu_types.h | 7 +++++++
drivers/iommu/amd/init.c | 2 ++
drivers/iommu/amd/iommu.c | 16 ++++++++++++++++
drivers/iommu/amd/iommufd.c | 14 ++++++++++++++
5 files changed, 43 insertions(+)
diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index b2ae17e3df34..f6cf412a9820 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -227,4 +227,8 @@ amd_iommu_make_clear_dte(struct iommu_dev_data *dev_data, struct dev_table_entry
struct iommu_domain *
amd_iommu_alloc_domain_nested(struct iommufd_viommu *viommu, u32 flags,
const struct iommu_user_data *user_data);
+
+/* Guest ID for vIOMMU */
+int amd_iommu_gid_alloc(struct amd_iommu *iommu);
+void amd_iommu_gid_free(struct amd_iommu *iommu, int gid);
#endif /* AMD_IOMMU_H */
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 688cd9240790..8c38775ff5c1 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -21,6 +21,7 @@
#include <linux/iommufd.h>
#include <linux/irqreturn.h>
#include <linux/generic_pt/iommu.h>
+#include <linux/idr.h>
#include <uapi/linux/iommufd.h>
@@ -404,6 +405,9 @@
#define MAX_DOMAIN_ID 65536
+/* Guest ID bits 0-14; bit 15 is reserved for secure vIOMMU. */
+#define VIOMMU_MAX_GID 0x7FFF
+
/* Timeout stuff */
#define LOOP_TIMEOUT 100000
#define MMIO_STATUS_TIMEOUT 2000000
@@ -501,6 +505,7 @@ struct amd_iommu_viommu {
struct iommufd_viommu core;
struct protection_domain *parent; /* nest parent domain for this viommu */
struct list_head pdom_list; /* For protection_domain->viommu_list */
+ u16 gid; /* Guest ID for the vIOMMU */
/*
* Per-vIOMMU guest domain ID to host domain ID mapping.
@@ -760,6 +765,8 @@ struct amd_iommu {
/* IOPF support */
struct iopf_queue *iopf_queue;
unsigned char iopfq_name[32];
+
+ struct ida gid_ida; /* guest IDs for this IOMMU */
};
static inline struct amd_iommu *dev_to_amd_iommu(struct device *dev)
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index c80872ce0b60..7b4cb473019d 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -1797,6 +1797,7 @@ static void __init free_iommu_one(struct amd_iommu *iommu)
free_ga_log(iommu);
iommu_unmap_mmio_space(iommu);
amd_iommu_iopf_uninit(iommu);
+ ida_destroy(&iommu->gid_ida);
}
static void __init free_iommu_all(void)
@@ -1885,6 +1886,7 @@ static int __init init_iommu_one(struct amd_iommu *iommu, struct ivhd_header *h,
raw_spin_lock_init(&iommu->lock);
iommu->cmd_sem_val = 0;
+ ida_init(&iommu->gid_ida);
/* Add IOMMU to internal data structures */
list_add_tail(&iommu->list, &amd_iommu_list);
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index c34a0f5a9540..fa9708af258e 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -257,6 +257,22 @@ static inline bool pdom_is_sva_capable(struct protection_domain *pdom)
return pdom_is_v2_pgtbl_mode(pdom) || pdom_is_in_pt_mode(pdom);
}
+int amd_iommu_gid_alloc(struct amd_iommu *iommu)
+{
+ int ret = ida_alloc_range(&iommu->gid_ida, 1, VIOMMU_MAX_GID, GFP_KERNEL);
+
+ if (ret >= 0)
+ pr_debug("%s: iommu devid=%#x, gid=%u\n", __func__, iommu->devid, ret);
+
+ return ret;
+}
+
+void amd_iommu_gid_free(struct amd_iommu *iommu, int gid)
+{
+ pr_debug("%s: iommu devid=%#x, gid=%u\n", __func__, iommu->devid, gid);
+ ida_free(&iommu->gid_ida, gid);
+}
+
static inline int get_acpihid_device_id(struct device *dev,
struct acpihid_map_entry **entry)
{
diff --git a/drivers/iommu/amd/iommufd.c b/drivers/iommu/amd/iommufd.c
index e8e7807f2a33..69a0e61bf83d 100644
--- a/drivers/iommu/amd/iommufd.c
+++ b/drivers/iommu/amd/iommufd.c
@@ -49,13 +49,23 @@ size_t amd_iommufd_get_viommu_size(struct device *dev, enum iommu_viommu_type vi
int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *parent,
const struct iommu_user_data *user_data)
{
+ int ret;
unsigned long flags;
struct protection_domain *pdom = to_pdomain(parent);
struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
+ struct amd_iommu *iommu = container_of(viommu->iommu_dev, struct amd_iommu, iommu);
+
+ if (!amd_iommu_viommu_enabled(iommu))
+ return -EOPNOTSUPP;
xa_init_flags(&aviommu->gdomid_array, XA_FLAGS_ALLOC1);
aviommu->parent = pdom;
+ ret = amd_iommu_gid_alloc(iommu);
+ if (ret < 0)
+ return ret;
+ aviommu->gid = ret;
+
viommu->ops = &amd_viommu_ops;
spin_lock_irqsave(&pdom->lock, flags);
@@ -70,11 +80,15 @@ static void amd_iommufd_viommu_destroy(struct iommufd_viommu *viommu)
unsigned long flags;
struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
struct protection_domain *pdom = aviommu->parent;
+ struct amd_iommu *iommu = container_of(viommu->iommu_dev, struct amd_iommu, iommu);
+
+ pr_debug("%s: gid=%#x, iommu devid=%#x\n", __func__, aviommu->gid, iommu->devid);
spin_lock_irqsave(&pdom->lock, flags);
list_del(&aviommu->pdom_list);
spin_unlock_irqrestore(&pdom->lock, flags);
xa_destroy(&aviommu->gdomid_array);
+ amd_iommu_gid_free(iommu, aviommu->gid);
}
/*
--
2.34.1