[RFC PATCH] sbi: add hardware isolation abstraction framework

[Raymond Mao <raymondmaoca@gmail.com>]

From: Raymond Mao <raymond.mao@riscstar.com>

Introduce a system-level hardware isolation framework with a
registration API and per-domain context tracking.
This establishes an abstraction that allows multiple mechanisms to
be composed while keeping core domain data structures independent
of any single platform implementation.

Signed-off-by: Raymond Mao <raymond.mao@riscstar.com>
---
 include/sbi/sbi_domain.h |   4 +
 include/sbi/sbi_hwiso.h  |  57 +++++++++++
 lib/sbi/objects.mk       |   1 +
 lib/sbi/sbi_hwiso.c      | 215 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 277 insertions(+)
 create mode 100644 include/sbi/sbi_hwiso.h
 create mode 100644 lib/sbi/sbi_hwiso.c

diff --git a/include/sbi/sbi_domain.h b/include/sbi/sbi_domain.h
index 02765777..fc7330a6 100644
--- a/include/sbi/sbi_domain.h
+++ b/include/sbi/sbi_domain.h
@@ -14,6 +14,7 @@
 #include <sbi/sbi_types.h>
 #include <sbi/sbi_hartmask.h>
 #include <sbi/sbi_domain_context.h>
+#include <sbi/sbi_hwiso.h>
 #include <sbi/sbi_rpxy.h>
 
 struct sbi_scratch;
@@ -199,6 +200,9 @@ struct sbi_domain {
 	bool system_reset_allowed;
 	/** Is domain allowed to suspend the system */
 	bool system_suspend_allowed;
+	/** Hardware isolation contexts for registered mechanisms */
+	struct sbi_hwiso_domain_ctx *hwiso_ctxs;
+	u32 hwiso_ctx_count;
 	/** Identifies whether to include the firmware region */
 	bool fw_region_inited;
 };
diff --git a/include/sbi/sbi_hwiso.h b/include/sbi/sbi_hwiso.h
new file mode 100644
index 00000000..adbeb715
--- /dev/null
+++ b/include/sbi/sbi_hwiso.h
@@ -0,0 +1,57 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * System-level hardware isolation framework
+ *
+ * Copyright (c) 2026 RISCstar Solutions Corporation.
+ *
+ * Author: Raymond Mao <raymond.mao@riscstar.com>
+ */
+
+#ifndef __SBI_HWISO_H__
+#define __SBI_HWISO_H__
+
+#include <sbi/sbi_types.h>
+
+struct sbi_domain;
+
+struct sbi_hwiso_ops {
+	const char *name;
+
+	/* Boot-time init */
+	int (*init)(void *fdt);
+
+	/* Per-domain init (domain_offset refers to domain instance node) */
+	int (*domain_init)(void *fdt, int domain_offset,
+			   struct sbi_domain *dom, void **ctx);
+
+	/* Before switching away from a domain */
+	void (*domain_exit)(const struct sbi_domain *src,
+			    const struct sbi_domain *dst, void *ctx);
+
+	/* After switching into a domain */
+	void (*domain_enter)(const struct sbi_domain *dst,
+			     const struct sbi_domain *src, void *ctx);
+
+	/* Optional cleanup */
+	void (*domain_cleanup)(struct sbi_domain *dom, void *ctx);
+};
+
+struct sbi_hwiso_domain_ctx {
+	const struct sbi_hwiso_ops *ops;
+	void *ctx;
+};
+
+int sbi_hwiso_register(const struct sbi_hwiso_ops *ops);
+
+int sbi_hwiso_init(void *fdt);
+int sbi_hwiso_domain_init(void *fdt, int domain_offset,
+			  struct sbi_domain *dom);
+
+void sbi_hwiso_domain_exit(const struct sbi_domain *src,
+			   const struct sbi_domain *dst);
+void sbi_hwiso_domain_enter(const struct sbi_domain *dst,
+			    const struct sbi_domain *src);
+void sbi_hwiso_domain_cleanup(struct sbi_domain *dom);
+
+#endif /* __SBI_HWISO_H__ */
diff --git a/lib/sbi/objects.mk b/lib/sbi/objects.mk
index ca312ee2..6091499a 100644
--- a/lib/sbi/objects.mk
+++ b/lib/sbi/objects.mk
@@ -72,6 +72,7 @@ libsbi-objs-y += sbi_domain.o
 libsbi-objs-y += sbi_emulate_csr.o
 libsbi-objs-y += sbi_fifo.o
 libsbi-objs-y += sbi_hart.o
+libsbi-objs-y += sbi_hwiso.o
 libsbi-objs-y += sbi_heap.o
 libsbi-objs-y += sbi_math.o
 libsbi-objs-y += sbi_hfence.o
diff --git a/lib/sbi/sbi_hwiso.c b/lib/sbi/sbi_hwiso.c
new file mode 100644
index 00000000..5f876b33
--- /dev/null
+++ b/lib/sbi/sbi_hwiso.c
@@ -0,0 +1,215 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * System-level hardware isolation framework
+ *
+ * Copyright (c) 2026 RISCstar Solutions Corporation.
+ *
+ * Author: Raymond Mao <raymond.mao@riscstar.com>
+ */
+
+#include <libfdt.h>
+#include <sbi/sbi_console.h>
+#include <sbi/sbi_domain.h>
+#include <sbi/sbi_error.h>
+#include <sbi/sbi_heap.h>
+#include <sbi/sbi_hwiso.h>
+#include <sbi/sbi_list.h>
+
+struct sbi_hwiso_node {
+	const struct sbi_hwiso_ops *ops;
+	struct sbi_dlist node;
+};
+
+static SBI_LIST_HEAD(hwiso_ops_list);
+static u32 hwiso_ops_count;
+
+static bool hwiso_ops_registered(const struct sbi_hwiso_ops *ops)
+{
+	struct sbi_hwiso_node *entry;
+
+	sbi_list_for_each_entry(entry, &hwiso_ops_list, node) {
+		if (entry->ops == ops)
+			return true;
+	}
+
+	return false;
+}
+
+int sbi_hwiso_register(const struct sbi_hwiso_ops *ops)
+{
+	struct sbi_hwiso_node *node;
+
+	if (!ops || !ops->name)
+		return SBI_EINVAL;
+
+	if (hwiso_ops_registered(ops))
+		return SBI_EALREADY;
+
+	node = sbi_zalloc(sizeof(*node));
+	if (!node)
+		return SBI_ENOMEM;
+
+	node->ops = ops;
+	SBI_INIT_LIST_HEAD(&node->node);
+	sbi_list_add_tail(&node->node, &hwiso_ops_list);
+	hwiso_ops_count++;
+
+	return 0;
+}
+
+int sbi_hwiso_init(void *fdt)
+{
+	struct sbi_hwiso_node *entry;
+	int rc;
+
+	sbi_list_for_each_entry(entry, &hwiso_ops_list, node) {
+		if (!entry->ops->init)
+			continue;
+
+		rc = entry->ops->init(fdt);
+		if (rc == SBI_ENOMEM)
+			return rc;
+		if (rc)
+			sbi_printf("hwiso: %s init failed (error %d)\n",
+				   entry->ops->name, rc);
+	}
+
+	return 0;
+}
+
+static void hwiso_warn_unknown_nodes(void *fdt, int domain_offset)
+{
+	int hoff, child;
+	struct sbi_hwiso_node *entry;
+	bool known;
+
+	if (!fdt || (domain_offset < 0))
+		return;
+
+	hoff = fdt_subnode_offset(fdt, domain_offset, "hw-isolation");
+	if (hoff < 0)
+		return;
+
+	fdt_for_each_subnode(child, fdt, hoff) {
+		known = false;
+		sbi_list_for_each_entry(entry, &hwiso_ops_list, node) {
+			if (!fdt_node_check_compatible(
+					fdt, child, entry->ops->name)) {
+				known = true;
+				break;
+			}
+		}
+
+		if (!known)
+			sbi_printf("hwiso: unknown mechanism at %s\n",
+				   fdt_get_name(fdt, child, NULL));
+	}
+}
+
+int sbi_hwiso_domain_init(void *fdt, int domain_offset,
+			  struct sbi_domain *dom)
+{
+	struct sbi_hwiso_node *entry;
+	struct sbi_hwiso_domain_ctx *ctxs;
+	void *ctx;
+	u32 idx = 0;
+	int rc;
+
+	if (!dom)
+		return 0;
+
+	if (!hwiso_ops_count) {
+		hwiso_warn_unknown_nodes(fdt, domain_offset);
+		return 0;
+	}
+
+	ctxs = sbi_calloc(sizeof(*ctxs), hwiso_ops_count);
+	if (!ctxs)
+		return SBI_ENOMEM;
+
+	dom->hwiso_ctxs = ctxs;
+	dom->hwiso_ctx_count = hwiso_ops_count;
+
+	sbi_list_for_each_entry(entry, &hwiso_ops_list, node) {
+		ctxs[idx].ops = entry->ops;
+		ctxs[idx].ctx = NULL;
+		ctx = NULL;
+
+		if (entry->ops->domain_init) {
+			rc = entry->ops->domain_init(fdt, domain_offset,
+						     dom, &ctx);
+			if (rc == SBI_ENOMEM) {
+				sbi_hwiso_domain_cleanup(dom);
+				return rc;
+			}
+			if (rc) {
+				sbi_printf("hwiso: %s domain init failed"
+					   " (error %d)\n",
+					   entry->ops->name, rc);
+				ctx = NULL;
+			}
+		}
+
+		ctxs[idx].ctx = ctx;
+		idx++;
+	}
+
+	hwiso_warn_unknown_nodes(fdt, domain_offset);
+
+	return 0;
+}
+
+void sbi_hwiso_domain_exit(const struct sbi_domain *src,
+			   const struct sbi_domain *dst)
+{
+	u32 i;
+
+	if (!src || !src->hwiso_ctxs)
+		return;
+
+	for (i = 0; i < src->hwiso_ctx_count; i++) {
+		if (!src->hwiso_ctxs[i].ops ||
+		    !src->hwiso_ctxs[i].ops->domain_exit)
+			continue;
+		src->hwiso_ctxs[i].ops->domain_exit(
+					src, dst, src->hwiso_ctxs[i].ctx);
+	}
+}
+
+void sbi_hwiso_domain_enter(const struct sbi_domain *dst,
+			    const struct sbi_domain *src)
+{
+	u32 i;
+
+	if (!dst || !dst->hwiso_ctxs)
+		return;
+
+	for (i = 0; i < dst->hwiso_ctx_count; i++) {
+		if (!dst->hwiso_ctxs[i].ops ||
+		    !dst->hwiso_ctxs[i].ops->domain_enter)
+			continue;
+		dst->hwiso_ctxs[i].ops->domain_enter(
+					dst, src, dst->hwiso_ctxs[i].ctx);
+	}
+}
+
+void sbi_hwiso_domain_cleanup(struct sbi_domain *dom)
+{
+	u32 i;
+
+	if (!dom || !dom->hwiso_ctxs)
+		return;
+
+	for (i = 0; i < dom->hwiso_ctx_count; i++) {
+		if (!dom->hwiso_ctxs[i].ops ||
+		    !dom->hwiso_ctxs[i].ops->domain_cleanup)
+			continue;
+		dom->hwiso_ctxs[i].ops->domain_cleanup(
+					dom, dom->hwiso_ctxs[i].ctx);
+	}
+
+	sbi_free(dom->hwiso_ctxs);
+	dom->hwiso_ctxs = NULL;
+	dom->hwiso_ctx_count = 0;
+}
-- 
2.25.1


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