Michael S. Tsirkin
2022-Jul-27 06:01 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 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? -- MST
Jason Wang
2022-Jul-27 06:54 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 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. I wonder if we can add a check in the core and fail the device registration in this case. Thanks> > > -- > MST >
Si-Wei Liu
2022-Jul-27 07:50 UTC
[PATCH V3 5/6] vDPA: answer num of queue pairs = 1 to userspace when VIRTIO_NET_F_MQ == 0
On 7/26/2022 11:01 PM, Michael S. Tsirkin 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? > >I guess this is spec thing (historical debt), I vaguely recall these fields are always present in config space regardless the existence of corresponding feature bit. -Siwei