[librm] Support ioremap() for addresses above 4GB in a 64-bit build

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/include/bits/iomap.h

@@ -9,4 +9,6 @@
 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
+#include <ipxe/iomap_pages.h>
+
 #endif /* _BITS_IOMAP_H */

src/arch/x86/include/ipxe/iomap_pages.h

@@ -0,0 +1,24 @@
+#ifndef _IPXE_IOMAP_PAGES_H
+#define _IPXE_IOMAP_PAGES_H
+
+/** @file
+ *
+ * I/O mapping API using page tables
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#ifdef IOMAP_PAGES
+#define IOMAP_PREFIX_pages
+#else
+#define IOMAP_PREFIX_pages __pages_
+#endif
+
+static inline __always_inline unsigned long
+IOMAP_INLINE ( pages, io_to_bus ) ( volatile const void *io_addr ) {
+	/* Not easy to do; just return the CPU address for debugging purposes */
+	return ( ( intptr_t ) io_addr );
+}
+
+#endif /* _IPXE_IOMAP_PAGES_H */

src/arch/x86/include/librm.h

@@ -378,6 +378,51 @@ struct interrupt_vector {
 
 extern void set_interrupt_vector ( unsigned int intr, void *vector );
 
+/** A page table */
+struct page_table {
+	/** Page address and flags */
+	uint64_t page[512];
+};
+
+/** Page flags */
+enum page_flags {
+	/** Page is present */
+	PAGE_P = 0x01,
+	/** Page is writable */
+	PAGE_RW = 0x02,
+	/** Page is accessible by user code */
+	PAGE_US = 0x04,
+	/** Page-level write-through */
+	PAGE_PWT = 0x08,
+	/** Page-level cache disable */
+	PAGE_PCD = 0x10,
+	/** Page is a large page */
+	PAGE_PS = 0x80,
+	/** Page is the last page in an allocation
+	 *
+	 * This bit is ignored by the hardware.  We use it to track
+	 * the size of allocations made by ioremap().
+	 */
+	PAGE_LAST = 0x800,
+};
+
+/** The I/O space page table */
+extern struct page_table io_pages;
+
+/** I/O page size
+ *
+ * We choose to use 2MB pages for I/O space, to minimise the number of
+ * page table entries required.
+ */
+#define IO_PAGE_SIZE 0x200000UL
+
+/** I/O page base address
+ *
+ * We choose to place I/O space immediately above the identity-mapped
+ * 32-bit address space.
+ */
+#define IO_BASE ( ( void * ) 0x100000000ULL )
+
 #endif /* ASSEMBLY */
 
 #endif /* LIBRM_H */