Since we don't currently tell the guest when the disk backend is
read-only, it will report any inconsistent read after write as an error.
An image may be read-only either because user requested it on the
command-line, or because write support isn't implemented. Pass the
read-only attribute using the VIRTIO_BLK_F_RO feature.
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
---
disk/core.c | 9 +++++++--
include/kvm/disk-image.h | 1 +
virtio/blk.c | 5 ++++-
3 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/disk/core.c b/disk/core.c
index dd2f258b0..4c7c4f030 100644
--- a/disk/core.c
+++ b/disk/core.c
@@ -139,8 +139,10 @@ static struct disk_image *disk_image__open(const char *filename, bool readonly,
/* blk device ?*/
disk = blkdev__probe(filename, flags, &st);
- if (!IS_ERR_OR_NULL(disk))
+ if (!IS_ERR_OR_NULL(disk)) {
+ disk->readonly = readonly;
return disk;
+ }
fd = open(filename, flags);
if (fd < 0)
@@ -150,13 +152,16 @@ static struct disk_image *disk_image__open(const char *filename, bool readonly,
disk = qcow_probe(fd, true);
if (!IS_ERR_OR_NULL(disk)) {
pr_warning("Forcing read-only support for QCOW");
+ disk->readonly = true;
return disk;
}
/* raw image ?*/
disk = raw_image__probe(fd, &st, readonly);
- if (!IS_ERR_OR_NULL(disk))
+ if (!IS_ERR_OR_NULL(disk)) {
+ disk->readonly = readonly;
return disk;
+ }
if (close(fd) < 0)
pr_warning("close() failed");
diff --git a/include/kvm/disk-image.h b/include/kvm/disk-image.h
index b72805242..4746e88c9 100644
--- a/include/kvm/disk-image.h
+++ b/include/kvm/disk-image.h
@@ -59,6 +59,7 @@ struct disk_image {
void *priv;
void *disk_req_cb_param;
void (*disk_req_cb)(void *param, long len);
+ bool readonly;
bool async;
int evt;
#ifdef CONFIG_HAS_AIO
diff --git a/virtio/blk.c b/virtio/blk.c
index a57df2e96..6e7a1ee36 100644
--- a/virtio/blk.c
+++ b/virtio/blk.c
@@ -148,10 +148,13 @@ static u8 *get_config(struct kvm *kvm, void *dev)
static u32 get_host_features(struct kvm *kvm, void *dev)
{
+ struct blk_dev *bdev = dev;
+
return 1UL << VIRTIO_BLK_F_SEG_MAX
| 1UL << VIRTIO_BLK_F_FLUSH
| 1UL << VIRTIO_RING_F_EVENT_IDX
- | 1UL << VIRTIO_RING_F_INDIRECT_DESC;
+ | 1UL << VIRTIO_RING_F_INDIRECT_DESC
+ | (bdev->disk->readonly ? 1UL << VIRTIO_BLK_F_RO : 0);
}
static void set_guest_features(struct kvm *kvm, void *dev, u32 features)
--
2.21.0
