[pc][multiboot] Use DMA for loading kernel and bootdata
Change-Id: I92e14c8237cb065ff77a78a3049ce70c83b692ca
diff --git a/pc-bios/multiboot.bin b/pc-bios/multiboot.bin
index e772713..a32b521 100644
--- a/pc-bios/multiboot.bin
+++ b/pc-bios/multiboot.bin
Binary files differ
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S
index b7efe4d..b40a2c1 100644
--- a/pc-bios/optionrom/multiboot.S
+++ b/pc-bios/optionrom/multiboot.S
@@ -26,7 +26,62 @@
#define GS_PROT_JUMP 0
#define GS_GDT_DESC 6
+#define GS_DMA_CTRL 12
+#define GS_DMA_LEN 16
+#define GS_DMA_ADDR1 20
+#define GS_DMA_ADDR2 24
+/* This macro assumes that gs:GS_DMA_* is set up as a scratch space */
+.macro do_dma data, addr, size
+ /* Struct (all fields are big-endian):
+ typedef struct FWCfgDmaAccess {
+ uint32_t control;
+ uint32_t length;
+ uint64_t address;
+ } FWCfgDmaAccess;
+ */
+ /* Set dma.control (big-endian):
+ high (16-bit) word is FW_CFG_INITRD_DATA
+ low (16-bit) word is FW_CFG_DMA_CTL_READ (0x02) |
+ FW_CFG_DMA_CTL_SELECT (0x08)
+ */
+ movl $(\data << 16 | 0x02 | 0x08), %eax
+ bswap %eax
+ mov %eax, %gs:GS_DMA_CTRL
+ /* Get the initrd's length and set dma.length. */
+ read_fw \size
+ bswap %eax
+ movl %eax, %gs:GS_DMA_LEN
+ /* Set dma.address */
+ /* read_fw clobbers edx, and puts the result in eax */
+ read_fw \addr
+ movl $0, %gs:GS_DMA_ADDR1
+ bswap %eax
+ mov %eax, %gs:GS_DMA_ADDR2
+ /* Kick off the DMA by outputting the physical address of dma to 0x514
+ (as two 32-bit values). */
+ /* The top value is always 0. */
+ xor %eax, %eax
+ mov $0x514, %dx
+ out %eax, (%dx)
+ /* Calculate the physical address of the DMA request structure stored, and
+ * send it to 0x514+4. */
+ mov %gs, %eax
+ movzwl %ax, %eax
+ shl $4, %eax
+ addl $GS_DMA_CTRL, %eax
+ bswap %eax
+ add $4, %dx
+ out %eax, (%dx)
+ /* Wait for DMA to finish */
+.Lwait_for_dma\@:
+ mov %gs:GS_DMA_CTRL, %eax
+ bswap %eax
+ test $~1, %eax
+ jnz .Lwait_for_dma\@
+.endm
+
+#define read_fw_dma(var) do_dma var ## _DATA, var ## _ADDR, var ## _SIZE
BOOT_ROM_START
@@ -67,14 +122,18 @@
xor %eax, %eax
mov %eax, %es
- /* Read the bootinfo struct into RAM */
- read_fw_blob(FW_CFG_INITRD)
+ /* Read the bootinfo struct into RAM using the DMA interface
+ TODO(teisenbe): Should really detect whether DMA is supported. */
+ read_fw_dma(FW_CFG_INITRD)
/* FS = bootinfo_struct */
read_fw FW_CFG_INITRD_ADDR
shr $4, %eax
mov %ax, %fs
+ /* Read the kernel and modules into RAM using the DMA interface */
+ read_fw_dma(FW_CFG_KERNEL)
+
/* Account for the EBDA in the multiboot structure's e801
* map.
*/
@@ -187,9 +246,6 @@
movl %eax, %fs
movl %eax, %gs
- /* Read the kernel and modules into RAM */
- read_fw_blob(FW_CFG_KERNEL)
-
/* Jump off to the kernel */
read_fw FW_CFG_KERNEL_ENTRY
mov %eax, %ecx
