efi_loader: Add bounce buffer support

Some hardware that is supported by U-Boot can not handle DMA above 32bits.
For these systems, we need to come up with a way to expose the disk interface
in a safe way.

This patch implements EFI specific bounce buffers. For non-EFI cases, this
apparently was no issue so far, since we can just define our environment
variables conveniently.

Signed-off-by: Alexander Graf <agraf@suse.de>

include/efi_loader.h

@@ -139,6 +139,11 @@ uint64_t efi_add_memory_map(uint64_t start, uint64_t pages, int memory_type,
 /* Called by board init to initialize the EFI memory map */
 int efi_memory_init(void);
 
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+extern void *efi_bounce_buffer;
+#define EFI_LOADER_BOUNCE_BUFFER_SIZE (64 * 1024 * 1024)
+#endif
+
 /* Convert strings from normal C strings to uEFI strings */
 static inline void ascii2unicode(u16 *unicode, char *ascii)
 {

lib/efi_loader/Kconfig

@@ -7,3 +7,12 @@ config EFI_LOADER
 	  on top of U-Boot. If this option is enabled, U-Boot will expose EFI
 	  interfaces to a loaded EFI application, enabling it to reuse U-Boot's
 	  device drivers.
+
+config EFI_LOADER_BOUNCE_BUFFER
+	bool "EFI Applications use bounce buffers for DMA operations"
+	depends on EFI_LOADER && ARM64
+	default n
+	help
+	  Some hardware does not support DMA to full 64bit addresses. For this
+	  hardware we can create a bounce buffer so that payloads don't have to
+	  worry about platform details.

lib/efi_loader/efi_disk.c

@@ -76,9 +76,6 @@ static efi_status_t EFIAPI efi_disk_rw_blocks(struct efi_block_io *this,
 	int blocks;
 	unsigned long n;
 
-	EFI_ENTRY("%p, %x, %"PRIx64", %lx, %p", this, media_id, lba,
-		  buffer_size, buffer);
-
 	diskobj = container_of(this, struct efi_disk_obj, ops);
 	if (!(desc = blk_get_dev(diskobj->ifname, diskobj->dev_index)))
 		return EFI_EXIT(EFI_DEVICE_ERROR);
@@ -95,10 +92,11 @@ static efi_status_t EFIAPI efi_disk_rw_blocks(struct efi_block_io *this,
 	if (buffer_size & (blksz - 1))
 		return EFI_EXIT(EFI_DEVICE_ERROR);
 
-	if (direction == EFI_DISK_READ)
+	if (direction == EFI_DISK_READ) {
 		n = desc->block_read(desc, lba, blocks, buffer);
-	else
+	} else {
 		n = desc->block_write(desc, lba, blocks, buffer);
+	}
 
 	/* We don't do interrupts, so check for timers cooperatively */
 	efi_timer_check();
@@ -116,16 +114,70 @@ static efi_status_t efi_disk_read_blocks(struct efi_block_io *this,
 			u32 media_id, u64 lba, unsigned long buffer_size,
 			void *buffer)
 {
-	return efi_disk_rw_blocks(this, media_id, lba, buffer_size, buffer,
-				  EFI_DISK_READ);
+	void *real_buffer = buffer;
+	efi_status_t r;
+
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+	if (buffer_size > EFI_LOADER_BOUNCE_BUFFER_SIZE) {
+		r = efi_disk_read_blocks(this, media_id, lba,
+			EFI_LOADER_BOUNCE_BUFFER_SIZE, buffer);
+		if (r != EFI_SUCCESS)
+			return r;
+		return efi_disk_read_blocks(this, media_id, lba +
+			EFI_LOADER_BOUNCE_BUFFER_SIZE / this->media->block_size,
+			buffer_size - EFI_LOADER_BOUNCE_BUFFER_SIZE,
+			buffer + EFI_LOADER_BOUNCE_BUFFER_SIZE);
+	}
+
+	real_buffer = efi_bounce_buffer;
+#endif
+
+	EFI_ENTRY("%p, %x, %"PRIx64", %lx, %p", this, media_id, lba,
+		  buffer_size, buffer);
+
+	r = efi_disk_rw_blocks(this, media_id, lba, buffer_size, real_buffer,
+			       EFI_DISK_READ);
+
+	/* Copy from bounce buffer to real buffer if necessary */
+	if ((r == EFI_SUCCESS) && (real_buffer != buffer))
+		memcpy(buffer, real_buffer, buffer_size);
+
+	return EFI_EXIT(r);
 }
 
 static efi_status_t efi_disk_write_blocks(struct efi_block_io *this,
 			u32 media_id, u64 lba, unsigned long buffer_size,
 			void *buffer)
 {
-	return efi_disk_rw_blocks(this, media_id, lba, buffer_size, buffer,
-				  EFI_DISK_WRITE);
+	void *real_buffer = buffer;
+	efi_status_t r;
+
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+	if (buffer_size > EFI_LOADER_BOUNCE_BUFFER_SIZE) {
+		r = efi_disk_write_blocks(this, media_id, lba,
+			EFI_LOADER_BOUNCE_BUFFER_SIZE, buffer);
+		if (r != EFI_SUCCESS)
+			return r;
+		return efi_disk_write_blocks(this, media_id, lba +
+			EFI_LOADER_BOUNCE_BUFFER_SIZE / this->media->block_size,
+			buffer_size - EFI_LOADER_BOUNCE_BUFFER_SIZE,
+			buffer + EFI_LOADER_BOUNCE_BUFFER_SIZE);
+	}
+
+	real_buffer = efi_bounce_buffer;
+#endif
+
+	EFI_ENTRY("%p, %x, %"PRIx64", %lx, %p", this, media_id, lba,
+		  buffer_size, buffer);
+
+	/* Populate bounce buffer if necessary */
+	if (real_buffer != buffer)
+		memcpy(real_buffer, buffer, buffer_size);
+
+	r = efi_disk_rw_blocks(this, media_id, lba, buffer_size, real_buffer,
+			       EFI_DISK_WRITE);
+
+	return EFI_EXIT(r);
 }
 
 static efi_status_t EFIAPI efi_disk_flush_blocks(struct efi_block_io *this)

lib/efi_loader/efi_memory.c

@@ -27,6 +27,10 @@ struct efi_mem_list {
 /* This list contains all memory map items */
 LIST_HEAD(efi_mem);
 
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+void *efi_bounce_buffer;
+#endif
+
 /*
  * Sorts the memory list from highest address to lowest address
  *
@@ -349,5 +353,17 @@ int efi_memory_init(void)
 	efi_add_memory_map(runtime_start, runtime_pages,
 			   EFI_RUNTIME_SERVICES_CODE, false);
 
+#ifdef CONFIG_EFI_LOADER_BOUNCE_BUFFER
+	/* Request a 32bit 64MB bounce buffer region */
+	uint64_t efi_bounce_buffer_addr = 0xffffffff;
+
+	if (efi_allocate_pages(1, EFI_LOADER_DATA,
+			       (64 * 1024 * 1024) >> EFI_PAGE_SHIFT,
+			       &efi_bounce_buffer_addr) != EFI_SUCCESS)
+		return -1;
+
+	efi_bounce_buffer = (void*)(uintptr_t)efi_bounce_buffer_addr;
+#endif
+
 	return 0;
 }