[PATCH] fix extboot from boot with cache=off

[Nolan <nolan@sigbus.net>]

Extboot submits requests with whatever buffer alignment the guest gave
to the BIOS.  This breaks with O_DIRECT disks, as they require 512 byte
alignment.

Most guest bootloaders sector align their requests out of paranoia, but
the OpenBSD bootloader does not.

This patch always copies.  Since extboot is only used at boot time to
load limited amounts of data, the overhead is not problematic.  I also
switched to using cpu_physical_memory_* instead of groveling around with
phys_ram_base directly.

Signed-off-by: Nolan Leake <nolan <at> sigbus.net>

---

 qemu/hw/extboot.c |   35 ++++++++++++++++++++++++-----------
 1 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/qemu/hw/extboot.c b/qemu/hw/extboot.c
index ada0fdd..ea16b3e 100644
--- a/qemu/hw/extboot.c
+++ b/qemu/hw/extboot.c
@@ -77,19 +77,29 @@ static void extboot_write_cmd(void *opaque, uint32_t addr, uint32_t value)
     BlockDriverState *bs = opaque;
     int cylinders, heads, sectors, err;
     uint64_t nb_sectors;
-
-    get_translated_chs(bs, &cylinders, &heads, &sectors);
+    target_phys_addr_t pa;
+    int blen;
+    void *buf = NULL;
 
     if (cmd->type == 0x01 || cmd->type == 0x02) {
-	target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.segment;
+	pa = cmd->xfer.segment * 16 + cmd->xfer.offset;
+        blen = cmd->xfer.nb_sectors * 512;
+        buf = qemu_memalign(512, blen);
+        if (!buf) {
+            printf("qemu_memalign failed\n");
+            return;
+        }
 
 	/* possible buffer overflow */
-	if ((pa + cmd->xfer.nb_sectors * 512) > phys_ram_size)
+	if ((pa + blen) > phys_ram_size) {
+            qemu_free(buf);
 	    return;
+        }
     }
 
     switch (cmd->type) {
     case 0x00:
+        get_translated_chs(bs, &cylinders, &heads, &sectors);
 	bdrv_get_geometry(bs, &nb_sectors);
 	cmd->query_geometry.cylinders = cylinders;
 	cmd->query_geometry.heads = heads;
@@ -98,22 +108,25 @@ static void extboot_write_cmd(void *opaque, uint32_t addr, uint32_t value)
 	cpu_physical_memory_set_dirty((value & 0xFFFF) << 4);
 	break;
     case 0x01:
-	err = bdrv_read(bs, cmd->xfer.sector, phys_ram_base +
-			cmd->xfer.segment * 16 + cmd->xfer.offset,
-			cmd->xfer.nb_sectors);
+	err = bdrv_read(bs, cmd->xfer.sector, buf, cmd->xfer.nb_sectors);
 	if (err)
 	    printf("Read failed\n");
+
+        cpu_physical_memory_write(pa, buf, blen);
+
 	break;
     case 0x02:
-	err = bdrv_write(bs, cmd->xfer.sector, phys_ram_base +
-			 cmd->xfer.segment * 16 + cmd->xfer.offset,
-			 cmd->xfer.nb_sectors);
+        cpu_physical_memory_read(pa, buf, blen);
+
+	err = bdrv_write(bs, cmd->xfer.sector, buf, cmd->xfer.nb_sectors);
 	if (err)
 	    printf("Write failed\n");
 
-	cpu_physical_memory_set_dirty(cmd->xfer.segment * 16 + cmd->xfer.offset);
 	break;
     }
+
+    if (buf)
+        qemu_free(buf);
 }
 
 void extboot_init(BlockDriverState *bs, int cmd)