tcm_vhost: Avoid VIRTIO_RING_F_EVENT_IDX feature bit
This patch adds a VHOST_SCSI_FEATURES mask minus VIRTIO_RING_F_EVENT_IDX
so that vhost-scsi-pci userspace will strip this feature bit once
GET_FEATURES reports it as being unsupported on the host.
This is to avoid a bug where ->handle_kicks() are missed when EVENT_IDX
is enabled by default in userspace code.
(mst: Rename to VHOST_SCSI_FEATURES + add comment)
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Asias He <asias@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c
index 43fb11e..2968b49 100644
--- a/drivers/vhost/tcm_vhost.c
+++ b/drivers/vhost/tcm_vhost.c
@@ -60,6 +60,15 @@
VHOST_SCSI_VQ_IO = 2,
};
+/*
+ * VIRTIO_RING_F_EVENT_IDX seems broken. Not sure the bug is in
+ * kernel but disabling it helps.
+ * TODO: debug and remove the workaround.
+ */
+enum {
+ VHOST_SCSI_FEATURES = VHOST_FEATURES & (~VIRTIO_RING_F_EVENT_IDX)
+};
+
#define VHOST_SCSI_MAX_TARGET 256
#define VHOST_SCSI_MAX_VQ 128
@@ -946,7 +955,7 @@
static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
{
- if (features & ~VHOST_FEATURES)
+ if (features & ~VHOST_SCSI_FEATURES)
return -EOPNOTSUPP;
mutex_lock(&vs->dev.mutex);
@@ -992,7 +1001,7 @@
return -EFAULT;
return 0;
case VHOST_GET_FEATURES:
- features = VHOST_FEATURES;
+ features = VHOST_SCSI_FEATURES;
if (copy_to_user(featurep, &features, sizeof features))
return -EFAULT;
return 0;