riscv: replace misleading va_kernel_pa_offset on XIP kernel

On XIP kernel, the name "va_kernel_pa_offset" is misleading: unlike
"normal" kernel, it is not the virtual-physical address offset of kernel
mapping, it is the offset of kernel mapping's first virtual address to
first physical address in DRAM, which is not meaningful because the
kernel's first physical address is not in DRAM.

For XIP kernel, there are 2 different offsets because the read-only part of
the kernel resides in ROM while the rest is in RAM. The offset to ROM is in
kernel_map.va_kernel_xip_pa_offset, while the offset to RAM is not stored
anywhere: it is calculated on-the-fly.

Remove this confusing "va_kernel_pa_offset" and add
"va_kernel_xip_data_pa_offset" as its replacement. This new variable is the
offset of virtual mapping of the kernel's data portion to the corresponding
physical addresses.

With the introduction of this new variable, also rename
va_kernel_xip_pa_offset -> va_kernel_xip_text_pa_offset to make it clear
that this one is about the .text section.
Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/84e5d005c1386d88d7b2531e0b6707ec5352ee54.1717789719.git.namcao@linutronix.deSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/page.h

@@ -112,11 +112,13 @@ struct kernel_mapping {
 	/* Offset between linear mapping virtual address and kernel load address */
 	unsigned long va_pa_offset;
 	/* Offset between kernel mapping virtual address and kernel load address */
-	unsigned long va_kernel_pa_offset;
-	unsigned long va_kernel_xip_pa_offset;
 #ifdef CONFIG_XIP_KERNEL
+	unsigned long va_kernel_xip_text_pa_offset;
+	unsigned long va_kernel_xip_data_pa_offset;
 	uintptr_t xiprom;
 	uintptr_t xiprom_sz;
+#else
+	unsigned long va_kernel_pa_offset;
 #endif
 };
 
@@ -134,12 +136,18 @@ extern phys_addr_t phys_ram_base;
 #else
 void *linear_mapping_pa_to_va(unsigned long x);
 #endif
+
+#ifdef CONFIG_XIP_KERNEL
 #define kernel_mapping_pa_to_va(y)	({					\
 	unsigned long _y = (unsigned long)(y);					\
-	(IS_ENABLED(CONFIG_XIP_KERNEL) && _y < phys_ram_base) ?			\
-		(void *)(_y + kernel_map.va_kernel_xip_pa_offset) :		\
-		(void *)(_y + kernel_map.va_kernel_pa_offset + XIP_OFFSET);	\
+	(_y < phys_ram_base) ?							\
+		(void *)(_y + kernel_map.va_kernel_xip_text_pa_offset) :	\
+		(void *)(_y + kernel_map.va_kernel_xip_data_pa_offset);		\
 	})
+#else
+#define kernel_mapping_pa_to_va(y) ((void *)((unsigned long)(y) + kernel_map.va_kernel_pa_offset))
+#endif
+
 #define __pa_to_va_nodebug(x)		linear_mapping_pa_to_va(x)
 
 #ifndef CONFIG_DEBUG_VIRTUAL
@@ -147,12 +155,17 @@ void *linear_mapping_pa_to_va(unsigned long x);
 #else
 phys_addr_t linear_mapping_va_to_pa(unsigned long x);
 #endif
+
+#ifdef CONFIG_XIP_KERNEL
 #define kernel_mapping_va_to_pa(y) ({						\
 	unsigned long _y = (unsigned long)(y);					\
-	(IS_ENABLED(CONFIG_XIP_KERNEL) && _y < kernel_map.virt_addr + XIP_OFFSET) ? \
-		(_y - kernel_map.va_kernel_xip_pa_offset) :			\
-		(_y - kernel_map.va_kernel_pa_offset - XIP_OFFSET);		\
+	(_y < kernel_map.virt_addr + XIP_OFFSET) ?				\
+		(_y - kernel_map.va_kernel_xip_text_pa_offset) :		\
+		(_y - kernel_map.va_kernel_xip_data_pa_offset);			\
 	})
+#else
+#define kernel_mapping_va_to_pa(y) ((unsigned long)(y) - kernel_map.va_kernel_pa_offset)
+#endif
 
 #define __va_to_pa_nodebug(x)	({						\
 	unsigned long _x = x;							\

arch/riscv/mm/init.c

@@ -1098,11 +1098,14 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	kernel_map.phys_addr = (uintptr_t)CONFIG_PHYS_RAM_BASE;
 	kernel_map.size = (uintptr_t)(&_end) - (uintptr_t)(&_start);
 
-	kernel_map.va_kernel_xip_pa_offset = kernel_map.virt_addr - kernel_map.xiprom;
+	kernel_map.va_kernel_xip_text_pa_offset = kernel_map.virt_addr - kernel_map.xiprom;
+	kernel_map.va_kernel_xip_data_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr
+						+ (uintptr_t)&_sdata - (uintptr_t)&_start;
 #else
 	kernel_map.page_offset = _AC(CONFIG_PAGE_OFFSET, UL);
 	kernel_map.phys_addr = (uintptr_t)(&_start);
 	kernel_map.size = (uintptr_t)(&_end) - kernel_map.phys_addr;
+	kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr;
 #endif
 
 #if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
@@ -1124,7 +1127,6 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	 */
 	kernel_map.va_pa_offset = IS_ENABLED(CONFIG_64BIT) ?
 				0UL : PAGE_OFFSET - kernel_map.phys_addr;
-	kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr;
 
 	/*
 	 * The default maximal physical memory size is KERN_VIRT_SIZE for 32-bit