userspace: add optional member to memory domains

Some systems may need to associate arch-specific data to
a memory domain. Add a Kconfig and `arch` field for this,
and a new arch API to initialize it.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/app_memory/mem_domain.h

@@ -64,6 +64,9 @@ struct k_mem_domain {
 	sys_dlist_t mem_domain_q;
 	/** number of partitions in the domain */
 	uint8_t num_partitions;
+#ifdef CONFIG_ARCH_MEM_DOMAIN_DATA
+	struct arch_mem_domain arch;
+#endif /* CONFIG_ARCH_MEM_DOMAIN_DATA */
 };
 #else
 /* To support use of IS_ENABLED for the APIs below */

include/sys/arch_interface.h

@@ -520,6 +520,26 @@ static inline bool arch_is_user_context(void);
  */
 int arch_mem_domain_max_partitions_get(void);
 
+#ifdef CONFIG_ARCH_MEM_DOMAIN_DATA
+/**
+ *
+ * @brief Architecture-specific hook for memory domain initialization
+ *
+ * Perform any tasks needed to initialize architecture-specific data within
+ * the memory domain, such as reserving memory for page tables. All members
+ * of the provided memory domain aside from `arch` will be initialized when
+ * this is called, but no threads will be a assigned yet.
+ *
+ * This function may fail if initializing the memory domain requires allocation,
+ * such as for page tables.
+ *
+ * @param domain The memory domain to initialize
+ * @retval 0 Success
+ * @retval -ENOMEM Insufficient memory
+ */
+int arch_mem_domain_init(struct k_mem_domain *domain);
+#endif /* CONFIG_ARCH_MEM_DOMAIN_DATA */
+
 /**
  * @brief Add a thread to a memory domain (arch-specific)
  *

kernel/Kconfig

@@ -696,6 +696,19 @@ config MAX_DOMAIN_PARTITIONS
 	help
 	  Configure the maximum number of partitions per memory domain.
 
+config ARCH_MEM_DOMAIN_DATA
+	bool
+	depends on USERSPACE
+	help
+	  This hidden option is selected by the target architecture if
+	  architecture-specific data is needed on a per memory domain basis.
+	  If so, the architecture defines a 'struct arch_mem_domain' which is
+	  embedded within every struct k_mem_domain. The architecture
+	  must also define the arch_mem_domain_init() function to set this up
+	  when a memory domain is created.
+
+	  Typical uses might be a set of page tables for that memory domain.
+
 menu "SMP Options"
 
 config USE_SWITCH

kernel/mem_domain.c

@@ -12,6 +12,10 @@
 #include <stdbool.h>
 #include <spinlock.h>
 
+#define LOG_LEVEL CONFIG_KERNEL_LOG_LEVEL
+#include <logging/log.h>
+LOG_MODULE_DECLARE(os);
+
 static struct k_spinlock lock;
 static uint8_t max_partitions;
 
@@ -124,6 +128,20 @@ void k_mem_domain_init(struct k_mem_domain *domain, uint8_t num_parts,
 
 	sys_dlist_init(&domain->mem_domain_q);
 
+#ifdef CONFIG_ARCH_MEM_DOMAIN_DATA
+	int ret = arch_mem_domain_init(domain);
+
+	/* TODO propagate return values, see #24609.
+	 *
+	 * Not using an assertion here as this is a memory allocation error
+	 */
+	if (ret != 0) {
+		LOG_ERR("architecture-specific initialization failed for domain %p with %d",
+			domain, ret);
+		k_panic();
+	}
+#endif
+
 	k_spin_unlock(&lock, key);
 }