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-rw-r--r--block.c15
-rw-r--r--block.h1
-rw-r--r--block_int.h3
-rw-r--r--hw/ide/core.c7
-rw-r--r--hw/scsi-disk.c4
5 files changed, 27 insertions, 3 deletions
diff --git a/block.c b/block.c
index 45ad6fb4b..da0930cbb 100644
--- a/block.c
+++ b/block.c
@@ -408,6 +408,16 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
}
bs->drv = drv;
bs->opaque = qemu_mallocz(drv->instance_size);
+
+ /*
+ * Yes, BDRV_O_NOCACHE aka O_DIRECT means we have to present a
+ * write cache to the guest. We do need the fdatasync to flush
+ * out transactions for block allocations, and we maybe have a
+ * volatile write cache in our backing device to deal with.
+ */
+ if (flags & (BDRV_O_CACHE_WB|BDRV_O_NOCACHE))
+ bs->enable_write_cache = 1;
+
/* Note: for compatibility, we open disk image files as RDWR, and
RDONLY as fallback */
if (!(flags & BDRV_O_FILE))
@@ -918,6 +928,11 @@ int bdrv_is_sg(BlockDriverState *bs)
return bs->sg;
}
+int bdrv_enable_write_cache(BlockDriverState *bs)
+{
+ return bs->enable_write_cache;
+}
+
/* XXX: no longer used */
void bdrv_set_change_cb(BlockDriverState *bs,
void (*change_cb)(void *opaque), void *opaque)
diff --git a/block.h b/block.h
index ea6905291..0ae252653 100644
--- a/block.h
+++ b/block.h
@@ -135,6 +135,7 @@ int bdrv_get_translation_hint(BlockDriverState *bs);
int bdrv_is_removable(BlockDriverState *bs);
int bdrv_is_read_only(BlockDriverState *bs);
int bdrv_is_sg(BlockDriverState *bs);
+int bdrv_enable_write_cache(BlockDriverState *bs);
int bdrv_is_inserted(BlockDriverState *bs);
int bdrv_media_changed(BlockDriverState *bs);
int bdrv_is_locked(BlockDriverState *bs);
diff --git a/block_int.h b/block_int.h
index 3e4b4a387..f95c80b90 100644
--- a/block_int.h
+++ b/block_int.h
@@ -158,6 +158,9 @@ struct BlockDriverState {
/* the memory alignment required for the buffers handled by this driver */
int buffer_alignment;
+ /* do we need to tell the quest if we have a volatile write cache? */
+ int enable_write_cache;
+
/* NOTE: the following infos are only hints for real hardware
drivers. They are not used by the block driver */
int cyls, heads, secs, translation;
diff --git a/hw/ide/core.c b/hw/ide/core.c
index fe5bd172a..6fd6dc247 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -148,8 +148,11 @@ static void ide_identify(IDEState *s)
put_le16(p + 83, (1 << 14) | (1 << 13) | (1 <<12) | (1 << 10));
/* 14=set to 1, 1=SMART self test, 0=SMART error logging */
put_le16(p + 84, (1 << 14) | 0);
- /* 14 = NOP supported, 0=SMART feature set enabled */
- put_le16(p + 85, (1 << 14) | 1);
+ /* 14 = NOP supported, 5=WCACHE enabled, 0=SMART feature set enabled */
+ if (bdrv_enable_write_cache(s->bs))
+ put_le16(p + 85, (1 << 14) | (1 << 5) | 1);
+ else
+ put_le16(p + 85, (1 << 14) | 1);
/* 13=flush_cache_ext,12=flush_cache,10=lba48 */
put_le16(p + 86, (1 << 14) | (1 << 13) | (1 <<12) | (1 << 10));
/* 14=set to 1, 1=smart self test, 0=smart error logging */
diff --git a/hw/scsi-disk.c b/hw/scsi-disk.c
index ffc2654bf..de8e314b1 100644
--- a/hw/scsi-disk.c
+++ b/hw/scsi-disk.c
@@ -709,7 +709,9 @@ static int32_t scsi_send_command(SCSIDevice *d, uint32_t tag,
memset(p,0,20);
p[0] = 8;
p[1] = 0x12;
- p[2] = 4; /* WCE */
+ if (bdrv_enable_write_cache(s->dinfo->bdrv)) {
+ p[2] = 4; /* WCE */
+ }
p += 20;
}
if ((page == 0x3f || page == 0x2a)