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Tsirkin" Cc: Wu Zongyong , virtualization , linux-kernel , wei.yang1@linux.alibaba.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 14, 2021 at 8:58 PM Michael S. Tsirkin wrote: > > On Tue, Sep 14, 2021 at 08:24:51PM +0800, Wu Zongyong wrote: > > This new attribute advertises whether the vdpa device is legacy or not. > > Users can pick right virtqueue size if the vdpa device is legacy which > > doesn't support to change virtqueue size. > > > > Signed-off-by: Wu Zongyong > > So if we are bothering with legacy, I think we'd better not. I guess the following may work: 1) disable the driver on BE host 2) present VERSION_1 with ACCESS_PLATFORM in get_features() 3) extend the management to advertise max_queue_size and min_queue_size, for ENI they are the same so management layer knows it needs to set the queue_size correctly during launching qemu Thoughts? Thanks > I think there are > several things to do when building the interface > - support transitional devices, that is allow userspace > to tell device it's in legacy mode > - support reporting/setting supporting endian-ness > > > --- > > drivers/vdpa/vdpa.c | 6 ++++++ > > drivers/virtio/virtio_vdpa.c | 7 ++++++- > > include/uapi/linux/vdpa.h | 1 + > > 3 files changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c > > index 1dc121a07a93..533d7f589eee 100644 > > --- a/drivers/vdpa/vdpa.c > > +++ b/drivers/vdpa/vdpa.c > > @@ -12,6 +12,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > > > @@ -494,6 +495,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > u16 max_vq_size; > > u32 device_id; > > u32 vendor_id; > > + u64 features; > > void *hdr; > > int err; > > > > @@ -508,6 +510,7 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > device_id = vdev->config->get_device_id(vdev); > > vendor_id = vdev->config->get_vendor_id(vdev); > > max_vq_size = vdev->config->get_vq_num_max(vdev); > > + features = vdev->config->get_features(vdev); > > > > err = -EMSGSIZE; > > if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev))) > > @@ -520,6 +523,9 @@ vdpa_dev_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid, u32 seq > > goto msg_err; > > if (nla_put_u16(msg, VDPA_ATTR_DEV_MAX_VQ_SIZE, max_vq_size)) > > goto msg_err; > > + if (features & BIT_ULL(VIRTIO_F_VERSION_1) && > > + nla_put_flag(msg, VDPA_ATTR_DEV_VERSION_1)) > > + goto msg_err; > > > > genlmsg_end(msg, hdr); > > return 0; > > diff --git a/drivers/virtio/virtio_vdpa.c b/drivers/virtio/virtio_vdpa.c > > index 72eaef2caeb1..1cba957c4cdc 100644 > > --- a/drivers/virtio/virtio_vdpa.c > > +++ b/drivers/virtio/virtio_vdpa.c > > @@ -7,6 +7,7 @@ > > * > > */ > > > > +#include "linux/virtio_config.h" > > #include > > #include > > #include > > @@ -145,6 +146,7 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index, > > /* Assume split virtqueue, switch to packed if necessary */ > > struct vdpa_vq_state state = {0}; > > unsigned long flags; > > + bool may_reduce_num = false; > > u32 align, num; > > int err; > > > > @@ -169,10 +171,13 @@ virtio_vdpa_setup_vq(struct virtio_device *vdev, unsigned int index, > > goto error_new_virtqueue; > > } > > > > + if (ops->get_features(vdpa) & BIT_ULL(VIRTIO_F_VERSION_1)) > > + may_reduce_num = true; > > + > > /* Create the vring */ > > align = ops->get_vq_align(vdpa); > > vq = vring_create_virtqueue(index, num, align, vdev, > > - true, true, ctx, > > + true, may_reduce_num, ctx, > > virtio_vdpa_notify, callback, name); > > if (!vq) { > > err = -ENOMEM; > > diff --git a/include/uapi/linux/vdpa.h b/include/uapi/linux/vdpa.h > > index 66a41e4ec163..ce0b74276a5b 100644 > > --- a/include/uapi/linux/vdpa.h > > +++ b/include/uapi/linux/vdpa.h > > @@ -32,6 +32,7 @@ enum vdpa_attr { > > VDPA_ATTR_DEV_VENDOR_ID, /* u32 */ > > VDPA_ATTR_DEV_MAX_VQS, /* u32 */ > > VDPA_ATTR_DEV_MAX_VQ_SIZE, /* u16 */ > > + VDPA_ATTR_DEV_VERSION_1, /* flag */ > > > > /* new attributes must be added above here */ > > VDPA_ATTR_MAX, > > -- > > 2.31.1 >