1 files changed, 294 insertions, 0 deletions
diff --git a/drivers/iommu/amd/nested.c b/drivers/iommu/amd/nested.c
new file mode 100644
index 000000000000..66cc36133c8b
--- /dev/null
+++ b/drivers/iommu/amd/nested.c
@@ -0,0 +1,294 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ */
+
+#define dev_fmt(fmt)	"AMD-Vi: " fmt
+
+#include <linux/iommu.h>
+#include <linux/refcount.h>
+#include <uapi/linux/iommufd.h>
+
+#include "amd_iommu.h"
+
+static const struct iommu_domain_ops nested_domain_ops;
+
+static inline struct nested_domain *to_ndomain(struct iommu_domain *dom)
+{
+	return container_of(dom, struct nested_domain, domain);
+}
+
+/*
+ * Validate guest DTE to make sure that configuration for host (v1)
+ * and guest (v2) page tables are valid when allocating nested domain.
+ */
+static int validate_gdte_nested(struct iommu_hwpt_amd_guest *gdte)
+{
+	u32 gpt_level = FIELD_GET(DTE_GPT_LEVEL_MASK, gdte->dte[2]);
+
+	/* Must be zero: Mode, Host-TPR */
+	if (FIELD_GET(DTE_MODE_MASK, gdte->dte[0]) != 0 ||
+	    FIELD_GET(DTE_HOST_TRP, gdte->dte[0]) != 0)
+		return -EINVAL;
+
+	/* GCR3 TRP must be non-zero if V, GV is set */
+	if (FIELD_GET(DTE_FLAG_V, gdte->dte[0]) == 1 &&
+	    FIELD_GET(DTE_FLAG_GV, gdte->dte[0]) == 1 &&
+	    FIELD_GET(DTE_GCR3_14_12, gdte->dte[0]) == 0 &&
+	    FIELD_GET(DTE_GCR3_30_15, gdte->dte[1]) == 0 &&
+	    FIELD_GET(DTE_GCR3_51_31, gdte->dte[1]) == 0)
+		return -EINVAL;
+
+	/* Valid Guest Paging Mode values are 0 and 1 */
+	if (gpt_level != GUEST_PGTABLE_4_LEVEL &&
+	    gpt_level != GUEST_PGTABLE_5_LEVEL)
+		return -EINVAL;
+
+	/* GLX = 3 is reserved */
+	if (FIELD_GET(DTE_GLX, gdte->dte[0]) == 3)
+		return -EINVAL;
+
+	/*
+	 * We need to check host capability before setting
+	 * the Guest Paging Mode
+	 */
+	if (gpt_level == GUEST_PGTABLE_5_LEVEL &&
+	    amd_iommu_gpt_level < PAGE_MODE_5_LEVEL)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+
+static void *gdom_info_load_or_alloc_locked(struct xarray *xa, unsigned long index)
+{
+	struct guest_domain_mapping_info *elm, *res;
+
+	elm = xa_load(xa, index);
+	if (elm)
+		return elm;
+
+	xa_unlock(xa);
+	elm = kzalloc(sizeof(struct guest_domain_mapping_info), GFP_KERNEL);
+	xa_lock(xa);
+	if (!elm)
+		return ERR_PTR(-ENOMEM);
+
+	res = __xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
+	if (xa_is_err(res))
+		res = ERR_PTR(xa_err(res));
+
+	if (res) {
+		kfree(elm);
+		return res;
+	}
+
+	refcount_set(&elm->users, 0);
+	return elm;
+}
+
+/*
+ * This function is assigned to struct iommufd_viommu_ops.alloc_domain_nested()
+ * during the call to struct iommu_ops.viommu_init().
+ */
+struct iommu_domain *
+amd_iommu_alloc_domain_nested(struct iommufd_viommu *viommu, u32 flags,
+			      const struct iommu_user_data *user_data)
+{
+	int ret;
+	struct nested_domain *ndom;
+	struct guest_domain_mapping_info *gdom_info;
+	struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
+
+	if (user_data->type != IOMMU_HWPT_DATA_AMD_GUEST)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	ndom = kzalloc(sizeof(*ndom), GFP_KERNEL);
+	if (!ndom)
+		return ERR_PTR(-ENOMEM);
+
+	ret = iommu_copy_struct_from_user(&ndom->gdte, user_data,
+					  IOMMU_HWPT_DATA_AMD_GUEST,
+					  dte);
+	if (ret)
+		goto out_err;
+
+	ret = validate_gdte_nested(&ndom->gdte);
+	if (ret)
+		goto out_err;
+
+	ndom->gdom_id = FIELD_GET(DTE_DOMID_MASK, ndom->gdte.dte[1]);
+	ndom->domain.ops = &nested_domain_ops;
+	ndom->domain.type = IOMMU_DOMAIN_NESTED;
+	ndom->viommu = aviommu;
+
+	/*
+	 * Normally, when a guest has multiple pass-through devices,
+	 * the IOMMU driver setup DTEs with the same stage-2 table and
+	 * use the same host domain ID (hDomId). In case of nested translation,
+	 * if the guest setup different stage-1 tables with same PASID,
+	 * IOMMU would use the same TLB tag. This will results in TLB
+	 * aliasing issue.
+	 *
+	 * The guest is assigning gDomIDs based on its own algorithm for managing
+	 * cache tags of (DomID, PASID). Within a single viommu, the nest parent domain
+	 * (w/ S2 table) is used by all DTEs. But we need to consistently map the gDomID
+	 * to a single hDomID. This is done using an xarray in the vIOMMU to
+	 * keep track of the gDomID mapping. When the S2 is changed, the INVALIDATE_IOMMU_PAGES
+	 * command must be issued for each hDomID in the xarray.
+	 */
+	xa_lock(&aviommu->gdomid_array);
+
+	gdom_info = gdom_info_load_or_alloc_locked(&aviommu->gdomid_array, ndom->gdom_id);
+	if (IS_ERR(gdom_info)) {
+		xa_unlock(&aviommu->gdomid_array);
+		ret = PTR_ERR(gdom_info);
+		goto out_err;
+	}
+
+	/* Check if gDomID exist */
+	if (refcount_inc_not_zero(&gdom_info->users)) {
+		ndom->gdom_info = gdom_info;
+		xa_unlock(&aviommu->gdomid_array);
+
+		pr_debug("%s: Found gdom_id=%#x, hdom_id=%#x\n",
+			  __func__, ndom->gdom_id, gdom_info->hdom_id);
+
+		return &ndom->domain;
+	}
+
+	/* The gDomID does not exist. We allocate new hdom_id */
+	gdom_info->hdom_id = amd_iommu_pdom_id_alloc();
+	if (gdom_info->hdom_id <= 0) {
+		__xa_cmpxchg(&aviommu->gdomid_array,
+			     ndom->gdom_id, gdom_info, NULL, GFP_ATOMIC);
+		xa_unlock(&aviommu->gdomid_array);
+		ret = -ENOSPC;
+		goto out_err_gdom_info;
+	}
+
+	ndom->gdom_info = gdom_info;
+	refcount_set(&gdom_info->users, 1);
+
+	xa_unlock(&aviommu->gdomid_array);
+
+	pr_debug("%s: Allocate gdom_id=%#x, hdom_id=%#x\n",
+		 __func__, ndom->gdom_id, gdom_info->hdom_id);
+
+	return &ndom->domain;
+
+out_err_gdom_info:
+	kfree(gdom_info);
+out_err:
+	kfree(ndom);
+	return ERR_PTR(ret);
+}
+
+static void set_dte_nested(struct amd_iommu *iommu, struct iommu_domain *dom,
+			   struct iommu_dev_data *dev_data, struct dev_table_entry *new)
+{
+	struct protection_domain *parent;
+	struct nested_domain *ndom = to_ndomain(dom);
+	struct iommu_hwpt_amd_guest *gdte = &ndom->gdte;
+	struct pt_iommu_amdv1_hw_info pt_info;
+
+	/*
+	 * The nest parent domain is attached during the call to the
+	 * struct iommu_ops.viommu_init(), which will be stored as part
+	 * of the struct amd_iommu_viommu.parent.
+	 */
+	if (WARN_ON(!ndom->viommu || !ndom->viommu->parent))
+		return;
+
+	parent = ndom->viommu->parent;
+	amd_iommu_make_clear_dte(dev_data, new);
+
+	/* Retrieve the current pagetable info via the IOMMU PT API. */
+	pt_iommu_amdv1_hw_info(&parent->amdv1, &pt_info);
+
+	/*
+	 * Use domain ID from nested domain to program DTE.
+	 * See amd_iommu_alloc_domain_nested().
+	 */
+	amd_iommu_set_dte_v1(dev_data, parent, ndom->gdom_info->hdom_id,
+			     &pt_info, new);
+
+	/* GV is required for nested page table */
+	new->data[0] |= DTE_FLAG_GV;
+
+	/* Guest PPR */
+	new->data[0] |= gdte->dte[0] & DTE_FLAG_PPR;
+
+	/* Guest translation stuff */
+	new->data[0] |= gdte->dte[0] & (DTE_GLX | DTE_FLAG_GIOV);
+
+	/* GCR3 table */
+	new->data[0] |= gdte->dte[0] & DTE_GCR3_14_12;
+	new->data[1] |= gdte->dte[1] & (DTE_GCR3_30_15 | DTE_GCR3_51_31);
+
+	/* Guest paging mode */
+	new->data[2] |= gdte->dte[2] & DTE_GPT_LEVEL_MASK;
+}
+
+static int nested_attach_device(struct iommu_domain *dom, struct device *dev,
+				struct iommu_domain *old)
+{
+	struct dev_table_entry new = {0};
+	struct iommu_dev_data *dev_data = dev_iommu_priv_get(dev);
+	struct amd_iommu *iommu = get_amd_iommu_from_dev_data(dev_data);
+	int ret = 0;
+
+	/*
+	 * Needs to make sure PASID is not enabled
+	 * for this attach path.
+	 */
+	if (WARN_ON(dev_data->pasid_enabled))
+		return -EINVAL;
+
+	mutex_lock(&dev_data->mutex);
+
+	set_dte_nested(iommu, dom, dev_data, &new);
+
+	amd_iommu_update_dte(iommu, dev_data, &new);
+
+	mutex_unlock(&dev_data->mutex);
+
+	return ret;
+}
+
+static void nested_domain_free(struct iommu_domain *dom)
+{
+	struct guest_domain_mapping_info *curr;
+	struct nested_domain *ndom = to_ndomain(dom);
+	struct amd_iommu_viommu *aviommu = ndom->viommu;
+
+	xa_lock(&aviommu->gdomid_array);
+
+	if (!refcount_dec_and_test(&ndom->gdom_info->users)) {
+		xa_unlock(&aviommu->gdomid_array);
+		return;
+	}
+
+	/*
+	 * The refcount for the gdom_id to hdom_id mapping is zero.
+	 * It is now safe to remove the mapping.
+	 */
+	curr = __xa_cmpxchg(&aviommu->gdomid_array, ndom->gdom_id,
+			    ndom->gdom_info, NULL, GFP_ATOMIC);
+
+	xa_unlock(&aviommu->gdomid_array);
+	if (WARN_ON(!curr || xa_err(curr)))
+		return;
+
+	/* success */
+	pr_debug("%s: Free gdom_id=%#x, hdom_id=%#x\n",
+		__func__, ndom->gdom_id, curr->hdom_id);
+
+	amd_iommu_pdom_id_free(ndom->gdom_info->hdom_id);
+	kfree(curr);
+	kfree(ndom);
+}
+
+static const struct iommu_domain_ops nested_domain_ops = {
+	.attach_dev = nested_attach_device,
+	.free = nested_domain_free,
+};