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>
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@ -60,6 +60,15 @@ enum {
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VHOST_SCSI_VQ_IO = 2,
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VHOST_SCSI_VQ_IO = 2,
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};
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};
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/*
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* VIRTIO_RING_F_EVENT_IDX seems broken. Not sure the bug is in
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* kernel but disabling it helps.
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* TODO: debug and remove the workaround.
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*/
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enum {
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VHOST_SCSI_FEATURES = VHOST_FEATURES & (~VIRTIO_RING_F_EVENT_IDX)
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};
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#define VHOST_SCSI_MAX_TARGET 256
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#define VHOST_SCSI_MAX_TARGET 256
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#define VHOST_SCSI_MAX_VQ 128
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#define VHOST_SCSI_MAX_VQ 128
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@ -946,7 +955,7 @@ static void vhost_scsi_flush(struct vhost_scsi *vs)
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static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
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static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
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{
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{
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if (features & ~VHOST_FEATURES)
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if (features & ~VHOST_SCSI_FEATURES)
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return -EOPNOTSUPP;
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return -EOPNOTSUPP;
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mutex_lock(&vs->dev.mutex);
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mutex_lock(&vs->dev.mutex);
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@ -992,7 +1001,7 @@ static long vhost_scsi_ioctl(struct file *f, unsigned int ioctl,
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return -EFAULT;
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return -EFAULT;
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return 0;
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return 0;
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case VHOST_GET_FEATURES:
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case VHOST_GET_FEATURES:
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features = VHOST_FEATURES;
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features = VHOST_SCSI_FEATURES;
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if (copy_to_user(featurep, &features, sizeof features))
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if (copy_to_user(featurep, &features, sizeof features))
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return -EFAULT;
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return -EFAULT;
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return 0;
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return 0;
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