riscv: fix the global name pfn_base confliction error

RISCV uses a global variable pfn_base for page/pfn translation. But this
is a common name and will be used elsewhere. In those cases, the
page-pfn macros which refer to this name will be referred to the
local/input variable instead. (such as in vfio_pin_pages_remote). This
make everything wrong.

This patch changes the name from pfn_base to riscv_pfn_base to fix
this problem.
Signed-off-by: Kenneth Lee <liguozhu@hisilicon.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/page.h

@@ -79,8 +79,8 @@ typedef struct page *pgtable_t;
 #endif
 
 #ifdef CONFIG_MMU
-extern unsigned long pfn_base;
-#define ARCH_PFN_OFFSET		(pfn_base)
+extern unsigned long riscv_pfn_base;
+#define ARCH_PFN_OFFSET		(riscv_pfn_base)
 #else
 #define ARCH_PFN_OFFSET		(PAGE_OFFSET >> PAGE_SHIFT)
 #endif /* CONFIG_MMU */

arch/riscv/mm/init.c

@@ -214,8 +214,8 @@ static struct pt_alloc_ops _pt_ops __initdata;
 #define pt_ops _pt_ops
 #endif
 
-unsigned long pfn_base __ro_after_init;
-EXPORT_SYMBOL(pfn_base);
+unsigned long riscv_pfn_base __ro_after_init;
+EXPORT_SYMBOL(riscv_pfn_base);
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
@@ -587,7 +587,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	kernel_map.va_pa_offset = PAGE_OFFSET - kernel_map.phys_addr;
 	kernel_map.va_kernel_pa_offset = kernel_map.virt_addr - kernel_map.phys_addr;
 
-	pfn_base = PFN_DOWN(kernel_map.phys_addr);
+	riscv_pfn_base = PFN_DOWN(kernel_map.phys_addr);
 
 	/* Sanity check alignment and size */
 	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);