LoongArch: mm: Add page table mapped mode support for virt_to_page()

According to LoongArch documentations, there are two types of address
translation modes: direct mapped address translation mode (DMW mode) and
page table mapped address translation mode (TLB mode).

Currently, virt_to_page() only supports direct mapped mode. This patch
determines which mode is used, and adds corresponding handling functions
for both modes.

For more details on the two modes, see [1].

[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#virtual-address-space-and-address-translation-modeSigned-off-by: Enze Li <lienze@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/page.h

@@ -84,7 +84,12 @@ typedef struct { unsigned long pgprot; } pgprot_t;
 #define sym_to_pfn(x)		__phys_to_pfn(__pa_symbol(x))
 
 #define virt_to_pfn(kaddr)	PFN_DOWN(PHYSADDR(kaddr))
-#define virt_to_page(kaddr)	pfn_to_page(virt_to_pfn(kaddr))
+
+#define virt_to_page(kaddr)								\
+({											\
+	(likely((unsigned long)kaddr < vm_map_base)) ?					\
+	dmw_virt_to_page((unsigned long)kaddr) : tlb_virt_to_page((unsigned long)kaddr);\
+})
 
 extern int __virt_addr_valid(volatile void *kaddr);
 #define virt_addr_valid(kaddr)	__virt_addr_valid((volatile void *)(kaddr))

arch/loongarch/include/asm/pgtable.h

@@ -353,6 +353,9 @@ static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *pt
 extern pgd_t swapper_pg_dir[];
 extern pgd_t invalid_pg_dir[];
 
+struct page *dmw_virt_to_page(unsigned long kaddr);
+struct page *tlb_virt_to_page(unsigned long kaddr);
+
 /*
  * The following only work if pte_present() is true.
  * Undefined behaviour if not..

arch/loongarch/mm/pgtable.c

@@ -9,6 +9,18 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 
+struct page *dmw_virt_to_page(unsigned long kaddr)
+{
+	return pfn_to_page(virt_to_pfn(kaddr));
+}
+EXPORT_SYMBOL_GPL(dmw_virt_to_page);
+
+struct page *tlb_virt_to_page(unsigned long kaddr)
+{
+	return pfn_to_page(pte_pfn(*virt_to_kpte(kaddr)));
+}
+EXPORT_SYMBOL_GPL(tlb_virt_to_page);
+
 pgd_t *pgd_alloc(struct mm_struct *mm)
 {
 	pgd_t *ret, *init;