Michael S. Tsirkin
2022-Jul-27 09:02 UTC
[PATCH V3 5/6] vDPA: answer num of queue pairs = 1 to userspace when VIRTIO_NET_F_MQ == 0
On Wed, Jul 27, 2022 at 02:54:13PM +0800, Jason Wang wrote:> On Wed, Jul 27, 2022 at 2:01 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > On Wed, Jul 27, 2022 at 03:47:35AM +0000, Parav Pandit wrote: > > > > > > > From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > Sent: Tuesday, July 26, 2022 10:53 PM > > > > > > > > On 7/27/2022 10:17 AM, Parav Pandit wrote: > > > > >> From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > >> Sent: Tuesday, July 26, 2022 10:15 PM > > > > >> > > > > >> On 7/26/2022 11:56 PM, Parav Pandit wrote: > > > > >>>> From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > >>>> Sent: Tuesday, July 12, 2022 11:46 PM > > > > >>>>> When the user space which invokes netlink commands, detects that > > > > >> _MQ > > > > >>>> is not supported, hence it takes max_queue_pair = 1 by itself. > > > > >>>> I think the kernel module have all necessary information and it is > > > > >>>> the only one which have precise information of a device, so it > > > > >>>> should answer precisely than let the user space guess. The kernel > > > > >>>> module should be reliable than stay silent, leave the question to > > > > >>>> the user space > > > > >> tool. > > > > >>> Kernel is reliable. It doesn?t expose a config space field if the > > > > >>> field doesn?t > > > > >> exist regardless of field should have default or no default. > > > > >> so when you know it is one queue pair, you should answer one, not try > > > > >> to guess. > > > > >>> User space should not guess either. User space gets to see if _MQ > > > > >> present/not present. If _MQ present than get reliable data from kernel. > > > > >>> If _MQ not present, it means this device has one VQ pair. > > > > >> it is still a guess, right? And all user space tools implemented this > > > > >> feature need to guess > > > > > No. it is not a guess. > > > > > It is explicitly checking the _MQ feature and deriving the value. > > > > > The code you proposed will be present in the user space. > > > > > It will be uniform for _MQ and 10 other features that are present now and > > > > in the future. > > > > MQ and other features like RSS are different. If there is no _RSS_XX, there > > > > are no attributes like max_rss_key_size, and there is not a default value. > > > > But for MQ, we know it has to be 1 wihtout _MQ. > > > "we" = user space. > > > To keep the consistency among all the config space fields. > > > > Actually I looked and the code some more and I'm puzzled: > > > > > > struct virtio_net_config config = {}; > > u64 features; > > u16 val_u16; > > > > vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config)); > > > > if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac), > > config.mac)) > > return -EMSGSIZE; > > > > > > Mac returned even without VIRTIO_NET_F_MAC > > > > > > val_u16 = le16_to_cpu(config.status); > > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16)) > > return -EMSGSIZE; > > > > > > status returned even without VIRTIO_NET_F_STATUS > > > > val_u16 = le16_to_cpu(config.mtu); > > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16)) > > return -EMSGSIZE; > > > > > > MTU returned even without VIRTIO_NET_F_MTU > > > > > > What's going on here? > > Probably too late to fix, but this should be fine as long as all > parents support STATUS/MTU/MAC.Why is this too late to fix.> I wonder if we can add a check in the core and fail the device > registration in this case. > > Thanks > > > > > > > -- > > MST > >
Jason Wang
2022-Jul-27 09:50 UTC
[PATCH V3 5/6] vDPA: answer num of queue pairs = 1 to userspace when VIRTIO_NET_F_MQ == 0
On Wed, Jul 27, 2022 at 5:03 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > On Wed, Jul 27, 2022 at 02:54:13PM +0800, Jason Wang wrote: > > On Wed, Jul 27, 2022 at 2:01 PM Michael S. Tsirkin <mst at redhat.com> wrote: > > > > > > On Wed, Jul 27, 2022 at 03:47:35AM +0000, Parav Pandit wrote: > > > > > > > > > From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > > Sent: Tuesday, July 26, 2022 10:53 PM > > > > > > > > > > On 7/27/2022 10:17 AM, Parav Pandit wrote: > > > > > >> From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > > >> Sent: Tuesday, July 26, 2022 10:15 PM > > > > > >> > > > > > >> On 7/26/2022 11:56 PM, Parav Pandit wrote: > > > > > >>>> From: Zhu, Lingshan <lingshan.zhu at intel.com> > > > > > >>>> Sent: Tuesday, July 12, 2022 11:46 PM > > > > > >>>>> When the user space which invokes netlink commands, detects that > > > > > >> _MQ > > > > > >>>> is not supported, hence it takes max_queue_pair = 1 by itself. > > > > > >>>> I think the kernel module have all necessary information and it is > > > > > >>>> the only one which have precise information of a device, so it > > > > > >>>> should answer precisely than let the user space guess. The kernel > > > > > >>>> module should be reliable than stay silent, leave the question to > > > > > >>>> the user space > > > > > >> tool. > > > > > >>> Kernel is reliable. It doesn?t expose a config space field if the > > > > > >>> field doesn?t > > > > > >> exist regardless of field should have default or no default. > > > > > >> so when you know it is one queue pair, you should answer one, not try > > > > > >> to guess. > > > > > >>> User space should not guess either. User space gets to see if _MQ > > > > > >> present/not present. If _MQ present than get reliable data from kernel. > > > > > >>> If _MQ not present, it means this device has one VQ pair. > > > > > >> it is still a guess, right? And all user space tools implemented this > > > > > >> feature need to guess > > > > > > No. it is not a guess. > > > > > > It is explicitly checking the _MQ feature and deriving the value. > > > > > > The code you proposed will be present in the user space. > > > > > > It will be uniform for _MQ and 10 other features that are present now and > > > > > in the future. > > > > > MQ and other features like RSS are different. If there is no _RSS_XX, there > > > > > are no attributes like max_rss_key_size, and there is not a default value. > > > > > But for MQ, we know it has to be 1 wihtout _MQ. > > > > "we" = user space. > > > > To keep the consistency among all the config space fields. > > > > > > Actually I looked and the code some more and I'm puzzled: > > > > > > > > > struct virtio_net_config config = {}; > > > u64 features; > > > u16 val_u16; > > > > > > vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config)); > > > > > > if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac), > > > config.mac)) > > > return -EMSGSIZE; > > > > > > > > > Mac returned even without VIRTIO_NET_F_MAC > > > > > > > > > val_u16 = le16_to_cpu(config.status); > > > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_STATUS, val_u16)) > > > return -EMSGSIZE; > > > > > > > > > status returned even without VIRTIO_NET_F_STATUS > > > > > > val_u16 = le16_to_cpu(config.mtu); > > > if (nla_put_u16(msg, VDPA_ATTR_DEV_NET_CFG_MTU, val_u16)) > > > return -EMSGSIZE; > > > > > > > > > MTU returned even without VIRTIO_NET_F_MTU > > > > > > > > > What's going on here? > > > > Probably too late to fix, but this should be fine as long as all > > parents support STATUS/MTU/MAC. > > Why is this too late to fix.If we make this conditional on the features. This may break the userspace that always expects VDPA_ATTR_DEV_NET_CFG_MTU? Thanks> > > I wonder if we can add a check in the core and fail the device > > registration in this case. > > > > Thanks > > > > > > > > > > > -- > > > MST > > > >