xtensa: userspace: swap page tables via assembly code

Since the necessary register values are now pre-computed and
stored in the memory domain struct, we can use them directly
in various assembly locations, thus replacing the function
call to xtensa_swap_update_page_tables().

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

Author: dcpleung

arch/xtensa/core/offsets/offsets.c

@@ -71,6 +71,18 @@ GEN_OFFSET_SYM(_thread_arch_t, return_ps);
 GEN_OFFSET_SYM(_thread_t, switch_handle);
 #ifdef CONFIG_XTENSA_MMU
 GEN_OFFSET_SYM(_thread_arch_t, ptables);
+
+GEN_OFFSET_SYM(_thread_t, mem_domain_info);
+GEN_OFFSET_SYM(_mem_domain_info_t, mem_domain);
+GEN_OFFSET_SYM(k_mem_domain_t, arch);
+
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_asid);
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_ptevaddr);
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_ptepin_as);
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_ptepin_at);
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_vecpin_as);
+GEN_OFFSET_SYM(arch_mem_domain_t, reg_vecpin_at);
+
 #endif
 #ifdef CONFIG_XTENSA_MPU
 GEN_OFFSET_SYM(_thread_arch_t, mpu_map);

arch/xtensa/core/ptables.c

@@ -1122,12 +1122,4 @@ int arch_buffer_validate(const void *addr, size_t size, int write)
 	return mem_buffer_validate(addr, size, write, XTENSA_MMU_USER_RING);
 }
 
-void xtensa_swap_update_page_tables(struct k_thread *incoming)
-{
-	struct arch_mem_domain *domain =
-		&(incoming->mem_domain_info.mem_domain->arch);
-
-	xtensa_mmu_set_paging(domain);
-}
-
 #endif /* CONFIG_USERSPACE */

arch/xtensa/core/userspace.S

@@ -271,7 +271,7 @@ xtensa_userspace_enter:
 
 	l32i a6, a1, 24
 #ifdef CONFIG_XTENSA_MMU
-	call4 xtensa_swap_update_page_tables
+	SWAP_PAGE_TABLE a6, a3, a7
 #endif
 #ifdef CONFIG_XTENSA_MPU
 	call4 xtensa_mpu_map_write

arch/xtensa/core/xtensa_asm2_util.S

@@ -248,11 +248,10 @@ xtensa_switch:
 	s32i a6, a1, 8
 	s32i a7, a1, 12
 
-	/* Switch page tables */
 	rsr a6, ZSR_CPU
 	l32i a6, a6, ___cpu_t_current_OFFSET
 #ifdef CONFIG_XTENSA_MMU
-	call4 xtensa_swap_update_page_tables
+	SWAP_PAGE_TABLE a6, a4, a7
 #endif
 #ifdef CONFIG_XTENSA_MPU
 	call4 xtensa_mpu_map_write

arch/xtensa/include/offsets_short_arch.h

@@ -17,6 +17,28 @@
 
 #define _thread_offset_to_ptables \
 	(___thread_t_arch_OFFSET + ___thread_arch_t_ptables_OFFSET)
+
+#define _thread_offset_to_mem_domain \
+	(___thread_t_mem_domain_info_OFFSET + ___mem_domain_info_t_mem_domain_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_asid \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_asid_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_ptevaddr \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_ptevaddr_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_ptepin_as \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_ptepin_as_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_ptepin_at \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_ptepin_at_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_vecpin_as \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_vecpin_as_OFFSET)
+
+#define _k_mem_domain_offset_to_arch_reg_vecpin_at \
+	(__k_mem_domain_t_arch_OFFSET + __arch_mem_domain_t_reg_vecpin_at_OFFSET)
+
 #endif /* CONFIG_USERSPACE */
 
 #endif /* ZEPHYR_ARCH_XTENSA_INCLUDE_OFFSETS_SHORT_ARCH_H_ */

arch/xtensa/include/xtensa_asm2_s.h

@@ -225,6 +225,44 @@
 
 .endm
 
+#if defined(CONFIG_XTENSA_MMU) && defined(CONFIG_USERSPACE)
+/*
+ * SWAP_PAGE_TABLE
+ *
+ * This swaps the page tables by using the pre-computed register values
+ * inside the architecture-specific memory domain struct.
+ *
+ * THREAD_PTR_REG is input containing pointer to the incoming thread struct.
+ * SC1_REG and SC2_REG are scratch registers.
+ *
+ * Note that all THREAD_PTR_REG, SC1_REG and SC2_REG are all clobbered.
+ * Restore the thread pointer after this if necessary.
+ */
+.macro SWAP_PAGE_TABLE THREAD_PTR_REG, SC1_REG, SC2_REG
+	l32i \THREAD_PTR_REG, \THREAD_PTR_REG, _thread_offset_to_mem_domain
+
+	j _swap_page_table_\@
+
+.align 16
+_swap_page_table_\@:
+	l32i \SC1_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_ptevaddr
+	l32i \SC2_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_asid
+	wsr \SC1_REG, PTEVADDR
+	wsr \SC2_REG, RASID
+
+	l32i \SC1_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_ptepin_as
+	l32i \SC2_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_ptepin_at
+	wdtlb \SC2_REG, \SC1_REG
+
+	l32i \SC1_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_vecpin_as
+	l32i \SC2_REG, \THREAD_PTR_REG, _k_mem_domain_offset_to_arch_reg_vecpin_at
+	wdtlb \SC2_REG, \SC1_REG
+
+	isync
+.endm
+
+#endif /* CONFIG_XTENSA_MMU && CONFIG_USERSPACE */
+
 /*
  * CROSS_STACK_CALL
  *
@@ -357,7 +395,7 @@ _xstack_call0_\@:
 	l32i a6, a6, ___cpu_t_current_OFFSET
 
 #ifdef CONFIG_XTENSA_MMU
-	call4 xtensa_swap_update_page_tables
+	SWAP_PAGE_TABLE a6, a3, a7
 #endif
 #ifdef CONFIG_XTENSA_MPU
 	call4 xtensa_mpu_map_write

include/zephyr/arch/xtensa/arch.h

@@ -81,6 +81,8 @@ struct arch_mem_domain {
 	sys_snode_t node;
 };
 
+typedef struct arch_mem_domain arch_mem_domain_t;
+
 /**
  * @brief Generate hardware exception.
  *

soc/cdns/dc233c/include/xtensa-dc233c.ld

@@ -162,7 +162,6 @@ SECTIONS
 
     /* Userspace related stuff */
     LIB_OBJ_FUNC_IN_SECT(libarch__xtensa__core.a,userspace.S.obj,xtensa_do_syscall)
-    LIB_OBJ_FUNC_IN_SECT(libarch__xtensa__core.a,ptables.c.obj,xtensa_swap_update_page_tables)
 
     /* Below are to speed up execution by avoiding TLB misses
      * on frequently used functions.