IDE is a bit ugly in this respect. For one it doesn't really keep track
of a sector size - most of the protocol is in units of 512 bytes, and we
assume 2048 bytes for CDROMs which is correct most of the time.
Second IDE allocates an I/O buffer long before we know if we're dealing
with a CDROM or not, so increase the alignment for the io_buffer
unconditionally.
Signed-off-by: Christoph Hellwig <h...@lst.de>
Index: qemu/hw/ide/core.c
===================================================================
--- qemu.orig/hw/ide/core.c 2010-09-12 18:30:06.000000000 -0300
+++ qemu/hw/ide/core.c 2010-09-12 18:32:29.133759395 -0300
@@ -2645,6 +2645,7 @@ int ide_init_drive(IDEState *s, BlockDri
if (bdrv_get_type_hint(bs) == BDRV_TYPE_CDROM) {
s->drive_kind = IDE_CD;
bdrv_set_change_cb(bs, cdrom_change_cb, s);
+ bs->buffer_alignment = 2048;
} else {
if (!bdrv_is_inserted(s->bs)) {
error_report("Device needs media, but drive is empty");
@@ -2679,7 +2680,8 @@ static void ide_init1(IDEBus *bus, int u
s->bus = bus;
s->unit = unit;
s->drive_serial = drive_serial++;
- s->io_buffer = qemu_blockalign(s->bs, IDE_DMA_BUF_SECTORS*512 + 4);
+ /* we need at least 2k alignment for accessing CDROMs using O_DIRECT */
+ s->io_buffer = qemu_memalign(2048, IDE_DMA_BUF_SECTORS*512 + 4);
s->io_buffer_total_len = IDE_DMA_BUF_SECTORS*512 + 4;
s->smart_selftest_data = qemu_blockalign(s->bs, 512);
s->sector_write_timer = qemu_new_timer(vm_clock,
